修訂版 3
最後更新：2013 年 6 月 24 日
版權所有 © 2012，Google Inc。保留所有權利。
compatibility@android.com
目錄
一、簡介
2.資源
3. 軟件
3.1.託管API 兼容性
3 .2。軟 API 兼容性
3.2.1.權限
3 .2.2。構建參數
3 .2.3。意圖兼容性
3.2.3.1.核心應用意圖
3 .2.3.2。意圖覆蓋
3 .2.3.3。意圖命名空間
3 .2.3.4。廣播意圖
3.3.本機API 兼容性
3.3.1 應用程序二進制接口
3.4.網絡兼容性
3.4.1. Web 視圖兼容性
3.4.2.瀏覽器兼容性
3.5. API 行為兼容性
3.6. API 命名空間
3.7.虛擬機兼容性
3 .8。用戶界面兼容性
3.8.1.小部件
3.8.2.通知
3 .8.3。搜索
3 .8.4。乾杯
3 .8.5。主題
3 .8.6。活沃爾論文
3 .8.7。最近申請顯示
3 .8.8。輸入管理設置
3 .8.9。鎖屏遙控器
3.9設備管理
3.10無障礙
3 .11 文字轉語音
4.應用程序封裝兼容性
5. 多媒體兼容性
5.1.媒體編解碼器
5.2.視頻編碼
5.3.聲音錄製
5.4.音頻延遲
5 .5。網絡協議
6.開發工具兼容性
7.硬件兼容性
7 .1。顯示和圖形
7.1.1.屏幕配置
7.1.2.顯示指標
7.1.3.屏幕方向
7 .1.4。 2D 和 3D 圖形加速
7 .1.5。遺留應用程序兼容模式
7 .1.6。屏幕類型
7 .1.7。屏幕技術
7.2.輸入設備
7 .2.1。鍵盤
7 .2.2。非觸摸導航
7.2.3.導航鍵
7.2.4.觸摸屏輸入
7.2.5.假觸摸輸入
7.2.6.麥克風
7.3.傳感器
7 .3.1。加速度計
7.3.1.加速度計
7 .3.2。磁力計
7 .3.3。全球定位系統
7 .3.4。陀螺儀
7 .3.5。晴雨表
7 .3.6。溫度計
7 .3.7。光度計
7 .3.8。接近傳感器
7 .4。數據連接
7.4.1.電話
7.4.2. IEEE 802.11（無線網絡）
7.4.2.1. WiFi直連
7.4.3.藍牙
7.4.4.近場通信
7 .4.5。最小網絡容量
7.5.照相機
7.5.1.後置攝像頭
7 .5.2。前置攝像頭
7 .5.3。相機 API 行為
7 .5.4。相機方向
7.6.內存和存儲
7.6.1.最小內存和存儲
7 .6.2。應用程序共享存儲
7.7.優盤
8.性能兼容性
9. 安全模型兼容性
9.1.權限
9 .2。 UID 和進程隔離
9 .3。文件系統權限
9.4.備用執行環境
10. 軟件兼容性測試
10.1.兼容性測試套件
10.2. CTS 驗證器
10.3.參考應用
11.可更新的軟件
12.聯繫我們
附錄 A - 藍牙測試程序
一、簡介
本文檔列舉了設備必須滿足的要求
兼容Android 4.1。
使用“必須”、“不得”、“必須”、“必須”、“不得”、“應該”、“不應該”、
“推薦”、“可能”和“可選”符合 RFC2119 中定義的 IETF 標準
[資源，1]。
如本文檔中所用，“設備實施者”或“實施者”是一個人或
開發運行 Android 4.1 的硬件/軟件解決方案的組織。一個裝置
implementation”或“implementation”是這樣開發的硬件/軟件解決方案。
要被視為與 Android 4.1 兼容，設備實現必須滿足
本兼容性定義中提出的要求，包括任何文件
通過引用併入。
本定義或第 10 節中描述的軟件測試沒有提及的地方，
模棱兩可或不完整，設備實施者有責任確保
與現有實現的兼容性。
為此，Android 開源項目 [Resources, 3] 既是參考資料
和 Android 的首選實現。設備實施者實力雄厚
鼓勵他們的實施最大程度地基於
“上游”源代碼可從 Android 開源項目獲得。雖然有些
假設組件可以替換為替代實現
強烈反對實��，因為通過軟件測試將成為
大y更難。實施者有責任確保完整的行為
與標準 Android 實現的兼容性，包括和超越
兼容性測試套件。最後 y，請注意某些組件替換和
本文檔明確禁止修改。
2.資源
1. IETF RFC2119 要求等級：http://www.ietf.org/rfc/rfc2119.txt
2. 安卓兼容方案概述：
http://source.android.com/compatibility/i index.html
3.安卓開源項目：http://source.android.com/
4. API定義和文檔：
http://developer.android.com/reference/packages.html
5.Android權限參考：
http://developer.android.com/reference/android/Manifest.permission.html
6. android.os.Build參考：
http://developer.android.com/reference/android/os/Build.html
7. Android 4.1 al owed version strings:
http://source.android.com/compatibility/4.1/versions.html
8.渲染腳本：
http://developer.android.com/guide/topics/graphics/renderscript.html
9. 硬件加速：
http://developer.android.com/guide/topics/graphics/hardware-accel.html
10.android.webkit.WebView類：
http://developer.android.com/reference/android/webkit/WebView.html
11. HTML5：http://www.whatwg.org/specs/web-apps/current-work/multipage/
12. HTML5 離線功能：http://dev.w3.org/html5/spec/Overview.html#offline
13. HTML5視頻標籤：http://dev.w3.org/html5/spec/Overview.html#video
14. HTML5/ W3C 地理定位 API：http://www.w3.org/TR/geolocation-API/
15. HTML5/W3C webdatabase PI: http://www.w3.org/TR/webdatabase/
16. HTML5/W3C IndexedDB API：http://www.w3.org/TR/IndexedDB/
17. Dalvik 虛擬機規範：在 Android 源代碼中可用，網址為
達爾維克/文檔
18. 應用小部件：
http://developer.android.com/guide/practices/ui_guidelines/widget_design.html
19.通知：
http://developer.android.com/guide/topics/ui/notifiers/notifications.html
20.應用資源：http://code.google.com/android/reference/available-
資源.html
21.狀態欄圖標樣式指南：
http://developer.android.com/guide/practices/ui_guidelines/icon_design_status_bar.html
22.搜索管理器：
http://developer.android.com/reference/android/app/SearchManager.html
23. Toasts：http://developer.android.com/reference/android/widget/Toast.html
24. 主題：http://developer.android.com/guide/topics/ui/themes.html
25. R.style類：h ttp ://developer.android.com/reference/android/R.style.html
26. Live Wal論文：http://developer.android.com/resources/articles/live-
wal文件.html
27.安卓設備管理：
http://developer.android.com/guide/topics/admin/device-admin.html
28. android.app.admin.DevicePolicyManager類：
http://developer.android.com/reference/android/app/admin/DevicePolicyManager.html
29. Android 無障礙服務 API：
http://developer.android.com/reference/android/accessibilityservice/package-
摘要.html
30. Android 輔助功能 API：
http://developer.android.com/reference/android/view/accessibility/package-
摘要.html
31. Eyes Free 項目：http://code.google.com/p/eyes-free
32. 文本轉語音 API ：
http://developer.android.com/reference/android/speech/tts/package-
摘要.html
33.參考工具文檔（adb、aapt、ddms）：
http://developer.android.com/guide/developing/tools/index.html
34.安卓apk文件說明：
http://developer.android.com/guide/topics/fundamentals.html
35.清單文件：http://developer.android.com/guide/topics/manifes t/manifest-
簡介.html
36.猴子測試工具：
https://developer.android.com/studio/test/other-testing-tools/monkey
37. Android android.content.pm.PackageManager 類和硬件特性
列表：
http://developer.android.com/reference/android/content/pm/PackageManager.html
38.支持多屏：
http://developer.android.com/guide/practices/screens_support.html
39. android.util.DisplayMetrics:
http://developer.android.com/reference/android/util/DisplayMetrics.html
40.android.content.res.配置：
http://developer.android.com/reference/android/content/res/Configuration.htm l
41. android.hardware.SensorEvent：
http://developer.android.com/reference/android/hardware/SensorEvent.html
42.藍牙API：
http://developer.android.com/reference/android/bluetooth/package-summary.html
43. NDEF 推送協議：http://source.android.com/compatibility/ndef-push-
協議.pdf
44. MIFARE MF1S503X：http://www.nxp.com/documents/data_sheet/MF1S503x.p df
45. MIFARE MF1S703X：http://www.nxp.com/documents/data_sheet/MF1S703x.p df
46. MIFARE MF0ICU1：http : //www.nxp.com/documents/data_sheet/MF0ICU1.pdf
47.MIFARE MF0ICU2：
http://www.nxp.com/documents/short_data_sheet/MF0ICU2_SDS.pdf
48. MIFARE AN130511：
http://www.nxp.com/documents/application_note/AN130511.pdf
49. MIFARE AN130411：
http://www.nxp.com/documents/application_note/AN130411.pdf
50.相機方向API：
http://developer.android.com/reference/android/hardware/Camera.html#setDisplayOrientation(int)
51. android.hardware.Camera:
http://developer.android.com/reference/android/hardware/Camera.html
52.安卓開放配件：
http://developer.android.com/guide/topics/usb/accessory.html
53. USB 主機 API：http://developer.android.com/guide/topics/usb/host.html
54. Android 安全和權限參考：
http://developer.android.com/guide/topics/security/security.html
55. Android 應用程序：http://code.google.com/p/apps-for-android
56. android.app.DownloadManager類：
http://developer.android.com/reference/android/app/DownloadManager.html
57. 安卓文件傳輸：http: //www.android.com/filetransfer
58. Android 媒體格式：http://developer.android.com/guide/appendix/media-
格式.html
59. HTTP Live Streaming Draft Protocol：http: //tools.ietf.org/html/d raft-pantos-http-
直播-03
60. NFC連接切換：http://www.nfc-
forum.org/specs/spec_list/#conn_handover
61.使用 NFC 的藍牙安全簡單配對：http://www.nfc-
forum.org/resources/AppDocs/NFCForum_AD_BTSSP_1_0.pdf
62. Wifi 多播 API：
http://developer.android.com/reference/android/net/wifi/WifiManager.MulticastLock.html
63.動作輔助：
http://developer.android.com/reference/android/content/Intent.html#ACTION_ASSIST
64. USB充電規格：
http://www.usb.org/developers/devclass_docs/USB_Battery_Charging_1.2.pdf
65. Android Beam： http://developer.android.com/guide/topics/nfc/nfc.html
66.安卓USB音頻：
http://developer.android.com/reference/android/hardware/usb/UsbConstants.html#USB_CLASS_AUDIO
67.安卓NFC共享設置：
http://developer.android.com/reference/android/provider/Settings.html#ACTION_NFCSHARING_SETTINGS
68. Wifi 直連（Wifi P2P）：
http://developer.android.com/reference/android/net/wifi/p2p/WifiP2pManager.html
69.媒體遠程控制客戶端：
http://developer.android.com/reference/android/media/RemoteControlClient.html
70.運動事件API：
http://developer.android.com/reference/android/view/MotionEvent.html
71.觸摸輸入配置：http://source.android.com/tech/input/touch-
設備.html
其中許多資源直接或間接源自 Android 4.1 SDK，
並且功能與該 SDK 文檔中的信息相同。在任何
此兼容性定義或兼容性測試套件不同意的情況
SDK文檔，SDK文檔被認為是權威的。任何
上述參考文獻中提供的技術細節由
包含成為此兼容性定義的一部分。
3. 軟件
3.1.託管 API 兼容性
託管（基於 Dalvik）執行環境是 Android 的主要載體
應用程序。 Android 應用程序編程接口 (API) 是一組
向託管 VM 中運行的應用程序公開的 Android 平台接口
環境。設備實現必須提供完整的實現，
包括所有記錄在案的行為，Android 公開的任何記錄在案的 API
4.1 SDK [資源，4]。
設備實現不得省略任何託管 API、更改 API 接口或
簽名，偏離記錄的行為，或包括空操作，除非
此兼容性定義特別允許。
此兼容性定義允許 Android 適用的某些類型的硬件
包括設備實現省略的 API。在這種情況下，API 必須
仍然在場並以合理的方式行事。具體見第7節
這個場景的要求。
3.2.軟 API 兼容性
除了第 3.1 節中的託管 API 之外，Android 還包括一個重要的
僅限運行時的“軟”API，以諸如意圖、權限和
無法在應用程序編譯時強制執行的 Android 應用程序的類似方面
時間。
3.2.1.權限
設備實現者必須支持和強制執行所有權限常量，因為
Permission 參考頁 [Resources, 5] 記錄了這一點。請注意，第 10 節
列出了與 Android 安全模型相關的其他要求。
3.2.2.構建參數
Android API 在 android.os.Build 類中包含許多常量
[Resources, 6] 旨在描述當前設備。提供一致的，
跨設備實現有意義的值，下表包括額外的
限制設備實現必須遵守的這些值的格式
符合。
範圍
註釋
當前執行的 Android 系統的版本，採用人類可讀的格式。該字段必須有一個
android.os.Build.VERSION.RELEASE
[Resources, 7] 中定義的字符串值。
當前執行的 Android 系統的版本，採用第三方應用程序代碼可訪問的格式。
android.os.Build.VERSION.SDK
對於 Android 4.1，此字段必須具有整數�� 16。
當前執行的 Android 系統的版本，採用第三方應用程序代碼可訪問的格式。
android.os.Build.VERSION.SDK_INT
對於 Android 4.1，此字段必須具有整數值 16。
設備實現者選擇的值，指定當前正在執行的 Android 的特定構建
系統，以人類可讀的格式。此值不得重複用於提供給不同的構建
android.os.Build.VERSION.INCREMENTAL
終端用戶。該字段的典型用途是指示哪個內部版本號或源代碼控制更改標識符是
用於生成構建。該字段的具體格式沒有要求，只是必須
不是 nul 或空字符串 ("")。
設備實現者選擇的一個值，用於標識設備使用的特定內部硬件，在
人類可讀的格式。該字段的一個可能用途是指示電路板供電的特定版本
android.os.Build.BOARD
裝置。該字段的值必須可編碼為 7 位 ASCI 並匹配正則表達式
“^[a-zA-Z0-9.,_-]+$”。
由設備實施者選擇的值，用於標識公司、組織、個人等的名稱。
誰生產了設備，以人類可讀的格式。該字段的一個可能用途是指示 OEM
android.os.Build.BRAND 品牌
和/或銷售該設備的運營商。該字段的值必須可編碼為 7 位 ASCI 並匹配
正則表達式“^[a-zA-Z0-9.,_-]+$”。
本機代碼的指令集（CPU 類型 + ABI 約定）的名稱。請參閱第 3.3 節：本機 API
android.os.Build.CPU_ABI
兼容性。
本機代碼的第二個指令集（CPU 類型 + ABI 約定）的名稱。請參閱第 3.3 節：本機
android.os.Build.CPU_ABI2
AP I 兼容性。
由設備實施者選擇的值，用於標識主體的特定配置或版本
android.os.Build.DEVICE
（有時稱為“工業設計”）的設備。該字段的值必須可編碼為 7 位
ASCI 並匹配正則表達式“^[a-zA-Z0-9.,_-]+$”。
唯一標識此構建的字符串。它應該是合理的人類可讀的。它必須遵循這個
模板：
$(BRAND)/$(PRODUCT)/$(DEVICE):$(VERSION.RELEASE)/$(ID)/$(VERSION.INCREMENTAL):$(TYPE)/$(TAGS)
例如：
android.os.Build.指紋
acme/mydevice/generic:4.1/JRN53/3359:userdebug/test-keys
指紋不得包含空白字符。如果上面模板中包含的其他字段有
空白字符，它們必須在構建指紋中替換為另一個字符，例如
下劃線 ("_") 字符。該字段的值必須可編碼為 7 位 ASCI。
硬件名稱（來自內核命令行或 /proc）。它應該是合理的人性化的——
android.os.Build.硬件
可讀。該字段的值必須可編碼為 7 位 ASCI 並匹配正則表達式“^[a-
zA-Z0-9.,_-]+$”。
一個字符串，以人類可讀的格式唯一標識構建所在的主機。沒有
android.os.Build.HOST
對該字段的特定格式有要求，除了它不能為 nul 或空字符串 ("")。
設備實施者選擇的標識符，以人類可讀格式引用特定版本。這個
字段可以與 android.os.Build.VERSION.INCREMENTAL 相同，但應該是一個足夠大的值
android.os.Build.ID
對最終用戶區分軟件構建有意義。該字段的值必須是可編碼的
作為 7 位 ASCI 並匹配正則表達式“^[a-zA-Z0-9.,_-]+$”。
產品原始設備製造商 (OEM) 的商標名稱。沒有要求
android.os.Build.MANUFACTURER
該字段的特定格式，除了它不能為 nul 或空字符串 ("")。
由設備實施者選擇的值，其中包含最終用戶已知的設備名稱。這個
android.os.Build.MODEL
應與設備營銷和銷售給最終用戶時使用的名稱相同。沒有
對該字段的特定格式有要求，除了它不能為 nul 或空字符串 ("")。
設備實施者選擇的一個值，包含產品的開發名稱或代號
android.os.Build.PRODUCT
（SKU）。必須是人類可讀的，但不一定供最終用戶查看。這個的價值
字段必須可編碼為 7 位 ASCI，並匹配正則表達式“^[a-zA-Z0-9.,_-]+$”。
硬件序列號（如果有）。該字段的值必須可編碼為 7 位 ASCI 並匹配
android.os.Build.SERIAL
正則表達式“^([a-zA-Z0-9]{0,20})$”。
設備實施者選擇的以逗號分隔的標籤列表，進一步區分構建。為了
android.os.Build.TAGS
例如，“未簽名，調試”。此字段的值必須可編碼為 7 位 ASCI 並匹配常規
表達式“^[a-zA-Z0-9.,_-]+$”。
android.os.Build.TIME
表示構建發生時間的時間戳的值。
由設備實現者選擇的值，指定構建的運行時配置。這個領域
應具有對應於三種典型 Android 運行時配置的值之一：“user”、
android.os.Build.TYPE
“userdebug”或“eng”。此字段的值必須可編碼為 7 位 ASCI 並匹配常規
表達式“^[a-zA-Z0-9.,_-]+$”。
生成構建的用戶（或自動用戶）的名稱或用戶 ID。沒有要求
android.os.Build.USER
該字段的特定格式，除了它不能為 nul 或空字符串 ("")。
3.2.3.意圖兼容性
設備實現必須遵循 Android 的鬆散耦合 Intent 系統，因為
在下面的部分中描述。 “榮幸”是指設備實施者
必須提供指定匹配 Intent 過濾器的 Android 活動或服務，並且
為每個指定的 Intent 模式綁定並實現正確的行為。
3.2.3.1.核心應用意圖
Android上游項目定義了一些核心應用，比如聯繫人，
日曆、相冊、音樂播放器等。設備實施者可以更換
這些應用程序具有替代版本。
但是，任何此類替代版本必須遵循提供的相同 Intent 模式
由上游項目。例如，如果設備包含替代音樂播放器，
它仍然必須遵守第三方應用程序發出的選擇歌曲的 Intent 模式。
以下應用程序被視為核心 Android 系統應用程序：
台鐘
瀏覽器
日曆
聯繫人
畫廊
全球搜索
啟動器
音樂
設置
核心Android系統應用包括各種Activity，或者Service組件
被認為是“公共”的。也就是說，屬性“android:exported”可能不存在，或者
可能具有值“true”。
對於在非核心 Android 系統應用程序之一中定義的每個活動或服務
通過值為“false”的 android:exported 屬性標記為非公開，設備
實現必須包含一個相同類型的組件來實現
與核心 Android 系統應用程序相同的 Intent 過濾器模式。
換句話說，設備實現可以取代核心 Android 系統應用程序；
但是，如果支持，���設備實現必須支持定義的所有 Intent 模式
被替換的每個核心 Android 系統應用程序。
3.2.3.2.意圖覆蓋
由於 Android 是一個可擴展的平台，設備實現必須允許每個 Intent
第 3.2.3.2 節中引用的模式將被第三方應用程序覆蓋。這
上游 Android 開源實現默認允許這樣做；設備
實施者不得將特殊特權附加到系統應用程序的使用
這些 Intent 模式，或阻止第三方應用程序綁定和假設
控制這些模式。此禁令具體包括但不限於
禁用允許用戶在多個選項之間進行選擇的“選擇器”用戶界面
處理相同 Intent 模式的應用程序。
但是，設備實現可以為特定 URI 提供默認活動
模式（例如 http://play.google.com）如果默認活動提供更具體的過濾器
對於數據 URI。例如，指定數據 URI 的意圖過濾器
“http://www.android.com”比“http://”的瀏覽器過濾器更具體。設備
實現必須為用戶提供一個用戶界面來修改默認活動
對於意圖。
3.2.3.3.意圖命名空間
設備實現不得包含支持任何
使用 ACTION、CATEGORY 或其他鍵的新 Intent 或 Broadcast Intent 模式
android.* 或 com.android.* 命名空間中的字符串。設備實施者不得
包含任何支持任何新 Intent 或 Broadcast Intent 模式的 Android 組件
在屬於的包空間中使用 ACTION、CATEGORY 或其他鍵字符串
另一個組織。設備實施者不得更改或擴展任何 Intent
3.2.3.1 節中列出的核心應用程序使用的模式。設備實現可能
包括使用名稱空間的 Intent 模式，這些模式清楚且明顯地與其相關聯
自己的組織。
此禁止類似於第 1 節中為 Java 語言類指定的禁止
3.6.
3.2.3.4.廣播意圖
第三方應用依賴平台廣播某些Intent來通知自己
硬件或軟件環境的變化。安卓兼容設備
必須廣播公共廣播意圖以響應適當的系統
事件。 SDK 文檔中描述了廣播意圖。
3.3.本機 API 兼容性
3.3.1 應用程序二進制接口
在 Dalvik 中運行的託管代碼可以調用應用程序中提供的本機代碼
.apk 文件作為 ELF .so 文件編譯為適當的設備硬件架構。
由於本機代碼高度依賴於底層處理器技術，Android
在 Android NDK 中定義了一些應用程序二進制接口 (ABI)，在文件中
文檔/CPU-ARCH-ABIS.html。如果設備實現與一個或多個兼容
定義的 ABI，它應該實現與 Android NDK 的兼容性，如下所示。
如果設備實現包括對 Android ABI 的支持，它：
必須包括對在託管環境中運行的代碼的支持以進行校準
本機代碼，使用標準的 Java 本機接口 (JNI) 語義。
必須是源代碼兼容的（即標頭兼容的）和二進制兼容的（例如
ABI）以及下面列表中的每個必需的庫
必須準確報告支持的本機應用程序二進制接口 (ABI)
由設備通過 android.os.Build.CPU_ABI API
必須僅報告最新版本的 Android 中記錄的那些 ABI
NDK，在文件 docs/CPU-ARCH-ABIS.txt 中
應該使用源代碼和頭文件構建
上游安卓開源項目
以下原生代碼 API 必須可供包含原生代碼的應用程序���用：
libc（C 庫）
libm（數學庫）
對 C++ 的最小支持
JNI接口
liblog（Android 日誌記錄）
libz（Zlib 壓縮）
libdl（動態鏈接器）
libGLESv1_CM.so (OpenGL ES 1.0)
libGLESv2.so（OpenGL ES 2.0）
libEGL.so（本機 OpenGL 表面管理）
libjnigraphics.so
libOpenSLES.so（OpenSL ES 1.0.1 音頻支持）
libOpenMAXAL.so（OpenMAX AL 1.0.1 支持）
libandroid.so（本機 Android 活動支持）
支持 OpenGL，如下所述
請注意，Android NDK 的未來版本可能會引入對其他功能的支持
ABI。如果設備實現與現有的預定義 ABI 不兼容，它
不得報告對任何 ABI 的支持。
本機代碼兼容性具有挑戰性。出於這個原因，應該重複
強烈建議設備實施者使用上游
上面列出的庫的實現，以幫助確保兼容性。
3.4.網絡兼容性
3.4.1. Web 視圖兼容性
Android 開源實現使用 WebKit 渲染引擎來
實現 android.webkit.WebView。因為開發一個不可行
Web 渲染系統的綜合測試套件，設備實現者必須使用
WebView 實現中 WebKit 的特定上游構建。具體 y：
設備實現的 android.webkit.WebView 實現必須是
基於來自上游 Android 開源樹的 534.30 WebKit 構建
適用於安卓 4.1。此構建包括一組特定的功能和安全性
WebView 的修復。設備實施者可以包括對
WebKit 實現；然而，任何此類定制不得改變
WebView 的行為，包括渲染行為。
WebView 報告的用戶代理字符串必須採用以下格式：
Mozilla/5.0 (Linux; U; Android $(VERSION); $(LOCALE); $(MODEL)
Build/$(BUILD)) AppleWebKit/534.30 (KHTML, like Gecko) 版本/4.1
移動 Safari/534.30
$(VERSION) 字符串的值必須與
$(VERSION) 字符串的值必須與
android.os.Build.VERSION.RELEASE
$(LOCALE) 字符串的值應該遵循 ISO 約定
國家代碼和語言，並且應該參考當前配置的
設備的語言環境
$(MODEL) 字符串的值必須與
android.os.Build.MODEL
$(BUILD) 字符串的值必須與
android.os.Build.ID
設備實現可以在用戶代理字符串中省略 Mobile
WebView 組件應該包括對 HTML5 盡可能多的支持
[資源, 11] 盡可能。最小 y，設備實現必須支持每個
WebView 中與 HTML5 關聯的這些 API：
應用程序緩存/離線操作 [資源，12]
<video> 標籤 [資源, 13]
地理定位 [資源, 14]
另外，設備實現必須支持 HTML5/W3C webstorage API
[資源，15]，並且應該支持 HTML5/W3C IndexedDB API [資源，
16]。請注意，隨著網絡開發標準機構正在轉變為支持
I ndexedDB over webstorage，IndexedDB有望成為必備
未來版本的 Android 中的���件。
HTML5 API 和所有 JavaScript API 一樣，必須在 WebView 中默認禁用，
除非開發人員通過常用的 Android API 明確啟用它們。
3.4.2.瀏覽器兼容性
設備實現必須包括一個獨立的瀏覽器應用程序，用於一般
用戶網頁瀏覽。獨立瀏覽器可以基於瀏覽器技術
除了 WebKit。但是，即使使用備用瀏覽器應用程序，
提供給第三方應用程序的 android.webkit.WebView 組件必須是
基於 WebKit，如第 3.4.1 節所述。
實現可以在獨立瀏覽器中發送自定義用戶代理字符串
應用。
獨立的瀏覽器應用程序（是否基於上游的 WebKit 瀏覽器
應用程序或第三方替代品）應該包括對盡可能多的支持
HTML5 [資源, 11] 盡可能。最小 y，設備實現必須支持
這些與 HTML5 相關的 API 中的每一個：
應用程序緩存/離線操作 [資源，12]
<video> 標籤 [資源, 13]
地理定位 [資源, 14]
另外，設備實現必須支持 HTML5/W3C webstorage API
[資源，15]，並且應該支持HTML5/W3C IndexedDB API [資源，
16]。請注意，隨著網絡開發標準機構正在轉變為支持
IndexedDB over webstorage，IndexedDB有望成為必備
未來版本的 Android 中的組件。
3.5. API 行為兼容性
每種 API 類型（託管、軟、本機和 Web）的行為必須是
與上游Android開源的首選實現一致
項目[資源，3]。一些特定的兼容性領域是：
設備不得更改標準 Intent 的行為或語義
設備不得改變特定類型的生命週期或生命週期語義
系統組件（如 Service、Activity、ContentProvider 等）
設備不得更改標準權限的語義
上面的列表並不全面。兼容性測試套件 (CTS) 測試
平台的重要部分用於行為兼容性，但不是全部。它是
實施者有責任確保與 Android 的行為兼容性
開源項目。出於這個原因，設備實現者應該使用源
盡可能通過 Android 開源項目獲得代碼，而不是重新
實施系統的重要部分。
3.6. API 命名空間
Android 遵循 Java 定義的包和類命名空間約定
編程語言。為確保與第三方應用程序的兼容性，設備
實施者不得對這些進行任何禁止的修改（見下文）
包命名空間：
java.*
javax.*
太陽。*
安卓。*
com.android.*
禁止的修改包括：
設備實現不得修改公開暴露的 API
Android 平台通過更改任何方法或類簽名，或通過刪除
類或類字段。
設備實現者可以修改 API 的底層實現，但是
此類修改不得影響規定的行為和 Java 語言
任何公開暴露的 API 的簽名。
設備實施者不得添加任何公開暴露的元素（例如
類或接口，或現有類或接口的字段或方法）到
上面的API。
“公開暴露的元素”是任何沒有用“@hide”修飾的結構
上游 Android 源代碼中使用的標記。換句話說，設備
實施者不得公開新的 API 或更改命名空間中的現有 API
上面提到。 Device implementers MAY make internal-only modifications, but those
modifications MUST NOT be advertised or otherwise exposed to developers.
Device implementers MAY add custom APIs, but any such APIs MUST NOT be in a
namespace owned by or referring to another organization. For instance, device
implementers MUST NOT add APIs to the com.google.* or similar namespace; only
Google may do so. Similarly, Google MUST NOT add APIs to other companies'
namespaces. Additional y, if a device implementation includes custom APIs outside
the standard Android namespace, those APIs MUST be packaged in an Android
shared library so that only apps that explicitly use them (via the <uses-library>
mechanism) are affected by the increased memory usage of such APIs.
If a device implementer proposes to improve one of the package namespaces above
(such as by adding useful new functionality to an existing API, or adding a new API), the
implementer SHOULD visit source.android.com and begin the process for contributing
changes and code, according to the information on that site.
Note that the restrictions above correspond to standard conventions for naming APIs in
the Java programming language; this section simply aims to reinforce those
conventions and make them binding through inclusion in this compatibility definition.
3.7. Virtual Machine Compatibility
Device implementations MUST support the ful Dalvik Executable (DEX) bytecode
specification and Dalvik Virtual Machine semantics [Resources, 17].
Device implementations MUST configure Dalvik to al ocate memory in accordance
with the upstream Android platform, and as specified b y the fol owing ta ble. (See
Section 7.1.1 for screen size and screen density definitions.)
Note that memory values specified below are considered minimum values, and device
i mplementation s MAY al ocate more memory per application.
Screen Size
Screen Density
Application Memory
smal / normal / large
ldpi / mdpi
16MB
smal / normal / large
tvdpi / hdpi
32MB
smal / normal / large
xhdpi
64MB
xlarge
mdpi
32MB
xlarge
tvdpi / hdpi
64MB
xlarge
xhdpi
128MB
3.8. User Interface Compatibility
3.8.1. Widgets
Android defines a component type and corresponding API and lifecycle that al ows
applications to expose an "AppWidget" to the end user [Re sources, 18]. The Android
Open Source reference release includes a Launcher application that includes user
interface affordances al owing the user to add, view, and remove AppWidgets from the
home screen.
Device implementations MAY substitute an alternative to the reference Launcher (ie
home screen). Alternative Launchers SHOULD include built-in support for AppWidgets,
and expose user interface affordances to add, configure, view, and remove
AppWidgets directly within the Launcher. Alternative Launchers MAY omit these user
interface elements; however, if they are omitted, the device implementation MUST
provide a separate application accessible from the Launcher that al ows users to add,
configure, view, and remove AppWidgets.
Device implementations MUST be capable of rendering widgets that are 4 x 4 in the
standard grid size. (See the App Widget Design Guidelines in the Android SDK
documentation [Resources, 18] for details.
3.8.2. Notifications
Android includes APIs that al ow developers to notify users of notable events
[Resources, 19], using hardware and software features of the device.
Some APIs al ow applications to perform notifications or attract attention using
hardware, specifical y sound, vibration, and light. Device implementations MUST
support notifications that use hardware features, as described in the SDK
documentation, and to the extent possible with the device implementation hardware.
For instance, if a device implementation includes a vibrator, it MUST correctly
implement the vibration APIs. If a device implementation lacks hardware, the
corresponding APIs MUST be implemented as no-ops. Note that this behavior is
further detailed in Section 7.
Additional y, the im plementatio n MUST correctly render al resources (icons, sound
files, etc.) provided for in the APIs [Resources, 20], or in the Status/System Bar icon
style guide [Resources, 21]. Device implementers MAY provide an alternative user
experience for notifications than that provided by the reference Android Open Source
implementati on; however, suc h alternative notification systems MUST support existing
notification resources, as above.
Android 4.1 includes support for rich notifications, such as interactive Views for
ongoing notifications. Device implementations MUST properly display and execute rich
notifications, as documented in the Android APIs.
3.8.3. Search
Android includes APIs [Resources, 22] that al ow developers to incorporate search into
their applications, and expose their application's data into the global system search.
General y speaking, this f unctionality cons ists of a single, system-wide user interface
that al ows users to enter queries, displays suggestions as users type, and displays
results. The Android APIs al ow developers to reuse this interface to provide search
within their own apps, and al ow developers to supply results to the common global
search user interface.
Device implementations MUST include a single, shared, system-wide search user
interface capable of real-time suggestions in response to user input. Device
implementations MUST implement the APIs that al ow developers to reuse this user
interface to provide search within their own applications. Device implementations
MUST implement the APIs that al ow third-party applications to add suggestions to the
search box when it is run in global search mode. If no third-party applications are
instal ed that make use of this functionality, the default behavior SHOULD be to display
web search engine results and suggestions.
3.8.4. Toasts
Applications can use the "Toast" API (defined in [Resources, 23]) to display short non-
modal strings to the end user, that disappear after a brief period of time. Device
implementations MUST display Toasts from applications to end users in some high-
visibility manner.
3.8.5. Themes
Android provides "themes" as a mechanism for applications to apply styles across an
entire Activity or application. Android 3.0 introduced a new "Holo" or "holographic"
theme as a set of defined styles for application developers to use if they want to match
the Holo theme look and feel as defined by the Android SDK [Resources, 24]. Device
implementations MUST NOT alter any of the Holo theme attributes exposed to
applications [ Resources, 25].
Android 4.0 introduced a new "Device Default" theme as a set of defined styles for
application developers to use if they want to match the look and feel of the device
theme as defined by the device implementer. Device implementations MAY modify the
DeviceDefault theme attributes exposed to applications [Re sources, 25].
3.8.6. Live Wallpapers
Android defines a component type and corresponding API and lifecycle that al ows
applications to expose one or more "Live Wal papers" to the end user [Resources, 26].
Live Wal papers are animations, patterns, or similar images with limited input
capabilities that display as a wal paper, behind other applications.
Hardware is considered capable of reliably running live wal papers if it can run al live
wal papers, with no limitations on functionality, at a reasonable framerate with no
adverse affects on other applications. If limitations in the hardware cause wal papers
and/or applications to crash, malfunction, consume excessive CPU or battery power, or
run at unacceptably low frame rates, the hardware is considered incapable of running
live wal paper. As an example, some live wal papers may use an Open GL 1.0 or 2.0
context to render their content. Live wal paper wil not run reliably on hardware that
does not support multiple OpenGL contexts because the live wal paper use of an
OpenGL context may conflict with other applications that also use an OpenGL context.
Device implementations capable of running live wal papers reliably as described
above SHOULD implement live wal papers. Device implementations determined to not
run live wal papers reliably as described above MUST NOT implement live wal papers.
3.8.7. Recent Application Display
The upstream Android 4.1 source code includes a user interface for displaying recent
applications using a thumbnail image of the application's graphical state at the
moment the user last left the application. Device implementations MAY alter or
eliminate this user interface; however, a future version of Android is planned to make
more extensive use of this functionality. Device implementations are strongly
encouraged to use the upstream Android 4.1 user interface (or a similar thumbnail-
based interface) for recent applications, or else they may not be compatible with a
future version of Android.
3.8.8. Input Management Settings
Android 4.1 includes support for Input Management Engines. The Android 4.1 APIs
al ow custom app IMEs to specify user-tunable settings. Device implementations
MUST include a way for the user to access IME settings at al times when an IME that
provides such user settings is displayed.
3.8.9. Lock Screen Remote Control
Android 4.0 introduced support for Remote Control API that lets media applications
integrate with playback controls that are displayed in a remote view like the device
lock screen [Resources, 69]. Device implementations SHOULD include support for
embedding remote controls in the device lock screen.
3.9 Device Administration
Android 4.1 includes features that al ow security-aware applications to perform device
administration functions at the system level, such as enforcing password policies or
performing remote wipe, through the Android Device Administration API [Resources,
27]. Device implementations MUST provide an implementation of the
DevicePolicyManager class [Resources, 28], and SHOULD support the ful range of
device administration policies defined in the Android SDK documentation [Resources,
27].
Note: while some of the requirements outlined above are stated as "SHOULD" for
Android 4.1, the Compatibility Definition for a future version is planned to change these
to "MUST". That is, these requirements are optional in Android 4.1 but will be
required by a future version. Existing and new devices that run Android 4.1 are very
strongly encouraged to meet these requirements in Android 4.1 , or they wil not
be able to attain Android compatibility when upgraded to the future version.
3.10 Accessibility
Android 4.1 provides an accessibility layer that helps users with disabilities to navigate
their devices more easily. In addition, Android 4.1 provides platform APIs that enable
accessibility service implementations to receive cal backs for user and system events
and generate alternate feedback mechanisms, such as text-to-speech, haptic
feedback, and trackbal /d-pad navigation [R esources, 29]. D evice implementations
MUST provide an implementation of the Android accessibility framework consistent
with the default Android implementation. Specifical y, device implementations MUST
meet the fol owing requirements.
Device implementations MUST support third party accessibility service
i mplementations through the android.accessibilityservice APIs [Resources,
30].
Device implementations MUST generate AccessibilityEvents and deliver
these events to al registered AccessibilityService implementations in a
manner consistent with the default Android implementation.
Device implementations MUST provide a user-accessible mechanism to enable
and disable accessibility services, and MUST display this interface in response
to the android.provider.Settings.ACTION_ACCESSIBILITY_SETTINGS intent.
Additional y, device implementations SHOULD provide an implementation of an
accessibility service on the device, and SHOULD provide a mechanism for users to
enable the accessibility service during device setup. An open source implementation
of an accessibility service is available from the Eyes Free project [Resources, 31].
3.11 Text-to-Speech
Android 4.1 includes APIs that al ow applications to make use of text-to-speech (TTS)
services, and al ows service providers to provide implementations of TTS services
[Resources, 32]. Device implementations MUST meet these requirements related to
t he Android TTS framework:
Device implementations MUST support the Android TTS framework APIs and
SHOULD include a TTS engine supporting the languages available on the
device. Note that the upstream Android open source software includes a ful -
featured TTS engine implementation.
Device implementations MUST support instal ation of third-party TTS engines.
Device implementations MUST provide a user-accessible interface that al ows
users to select a TTS engine for use at the system level.
4. Application Packaging Compatibility
Device implementations MUST instal and run Android ".apk" files as generated by the
"aapt" tool included in the official Android SDK [Resources, 33].
Devices implementations MUST NOT extend eithe r the .apk [Reso urces, 34], Android
Manifest [Resources, 35], Dalvik bytecode [Resources, 17], or renderscript bytecode
formats in such a way that would prevent those files from instal in g and running co rrectly
on other c ompatible device s. Device impleme nters SHOULD u se the reference
upstream implementation of Dalvik, and the reference implementation's package
management system.
5. Multimedia Compatibility
Device implementations MUST include at least one form of audio output, such as
speakers, headphone jack, external speaker connection, etc.
5.1. Media Codecs
Device implementations MUST support the core media formats specified in the
Android SDK documentation [Resources, 58] except where explicitly permitted in this
document. Specifical y, device implementations MUST support the media formats,
encoders, decoders, file types and container formats defined in the tables below. Al of
these codecs are provided as s oftware impleme ntations in the preferred Android
implementation from the Android Open Source Project.
Please note that neither Google nor the Open Handset Alliance make any
representation that these codecs are unencumbered by third-party patents.
Those intending to use this source code in hardware or software products are
advised that implementations of this code, including in open source software
or shareware, may require patent licenses from the relevant patent holders.
Note that these tables do not list specific bitrate requirements for most video codecs
because current device hardware does not necessarily support bitrates that map
exactly to the required bitrates specified by the relevant standards. Instead, device
implementations SHOULD support the highest bitrate practical on the hardware, up to
the limits defined by the specifications.
File Type(s) /
Format /
Type
Encoder
Decoder
Details
Container
Codec
Formats
Support for
REQUIRED
mono/stereo/5.0/5.1*
MPEG-4
Required for device implementations
content with
AAC Profile
that include microphone hardware
REQUIRED
standard sampling
(AAC LC)
and define
3GPP
rates from 8 to 48
android.hardware.microphone.
(.3gp)
kHz.
MPEG-4
Support for
(.mp4,
MPEG-4
mono/stereo/5.0/5.1*
.m4a)
HE AAC
content with
ADTS raw
REQUIRED
Profile
standard sampling
AAC (.aac,
(AAC+)
rates from 16 to 48
decode in
kHz.
Android
3.1+,
Support for
MPEG-4
REQUIRED for device
encode in
mono/stereo/5.0/5.1*
HE AAC v2
implementations that include
Android
content with
Profile
microphone hardware and
4.0+, ADIF
standard sampling
(enhanced
define
not
rates from 16 to 48
AAC+)
android.hardware.microphone
supported)
kHz.
MPEG-TS
MPEG-4
(.ts, not
Audio
REQUIRED for device
Support for
seekable,
Object Type
implementations that include
mono/stereo content
Android
ER AAC
microphone hardware and
REQUIRED
with standard
3.0+)
ELD
define
sampling rates from
(Enhanced
android.hardware.microphone
16 to 48 kHz.
Low Delay
AAC)
REQUIRED
Required for device implementations
4.75 to 12.2 kbps
AMR-NB
that include microphone hardware
REQUIRED
3GPP (.3gp)
sampled @ 8kHz
and define
android.hardware.microphone.
REQUIRED
Required for device implementations
9 rates from 6.60
AMR-WB
that include microphone hardware
REQUIRED
kbit/s to 23.85 kbit/s
3GPP (.3gp)
and define
sampled @ 16kHz
android.hardware.microphone.
Mono/Stereo (no
multichannel).
Audio
Sample rates up to
48 kHz (but up to
44.1 kHz is
recommended on
devices with 44.1
REQUIRED
FLAC
kHz output, as the 48
FLAC (.flac) only
(Android 3.1+)
to 44.1 kHz
downsampler does
not include a low-
pass filter). 16-bit
recommended; no
dither applied for 24-
bit.
Mono/Stereo 8-
320Kbps constant
MP3
REQUIRED
MP3 (.mp3)
(CBR) or variable
bit-rate (VBR)
Type 0 and
MIDI Type 0 and 1.
1 (.mid,
DLS Version 1 and
.xmf, .mxmf)
2. XMF and Mobile
RTTTL/RTX
MIDI
REQUIRED
XMF. Support for
(.rtttl, .rtx)
ringtone formats
OTA (.ota)
RTTTL/RTX, OTA,
iMelody
and iMelody
(.imy)
Ogg (.ogg)
Vorbis
REQUIRED
Matroska
(.mkv)
8-bit and 16-bit
linear PCM** (rates
up to limit of
hardware).Devices
MUST support
PCM/WAVE
REQUIRED
REQUIRED
WAVE (.wav)
sampling rates for
raw PCM recording
at 8000,16000 and
44100 Hz
frequencies
JPEG
REQUIRED
REQUIRED
Base+progressive
JPEG (.jpg)
GIF
REQUIRED
GIF (.gif)
Image
PNG
REQUIRED
REQUIRED
PNG (.png)
BMP
REQUIRED
BMP (.bmp)
WEBP
REQUIRED
REQUIRED
WebP (.webp)
REQUIRED
Required for device implementations
3GPP
that include camera hardware and
(.3gp)
H.263
REQUIRED
define android.hardware.camera
MPEG-4
or
(.mp4)
android.hardware.camera.front.
3GPP
(.3gp)
REQUIRED
MPEG-4
(.mp4)
Required for device implementations
MPEG-TS
that include camera hardware and
Baseline Profile
Video
H.264 AVC
REQUIRED
(.ts, AAC
define android.hardware.camera
(BP)
audio only,
or
not
android.hardware.camera.front.
seekable,
Android
3.0+)
MPEG-4
REQUIRED
3GPP (.3gp)
SP
WebM (.webm)
REQUIRED
and Matroska
VP8
(Android
(.mkv, Android
2.3.3+)
4.0+)
*Note: Only downmix of 5.0/5.1 content is required; recording or rendering more than 2
channels is optional. **Note: 16-bit linear PCM capture is mandatory. 8-bit linear PCM
capture is not mandatory.
5.2 Video Encoding
Android device implementations that include a rear-facing camera and declare
android.hardware.camera SHOULD support the fol owing video encoding profiles.
HD (When supported by
SD (Low quality) SD (High quality)
hardware)
H.264 Baseline
H.264 Baseline
Video codec
H.264 Baseline Profile
Profile
Profile
Video
176 x 144 px
480 x 360 px
1280 x 720 px
resolution
Video frame 12 fps
30 fps
30 fps
rate
500 Kbps or
Video bitrate 56 Kbps
2 Mbps or higher
higher
Audio codec AAC-LC
AAC-LC
AAC-LC
Audio
1 (mono)
2 (stereo)
2 (stereo)
channels
Audio bitrate 24 Kbps
128 Kbps
192 Kbps
5.3. Audio Recording
When an application has used the android.media.AudioRecord API to start recording
an audio stream, device implementations that include microphone hardware and
declare android.hardware.microphone MUST sample and record audio with each of
these behaviors:
The device SHOULD exhibit approximately flat amplitude versus frequency
characteristics; specifical y, ±3 dB, from 100 Hz to 4000 Hz
Audio input sensitivity SHOULD be set such that a 90 dB sound power level
(SPL) source at 1000 Hz yields RMS of 2500 for 16-bit samples.
PCM amplitude levels SHOULD linearly track input SPL changes over at least a
30 dB range from -18 dB to +12 dB re 90 dB SPL at the microphone.
Total harmonic distortion SHOULD be less than 1% for 1Khz at 90 dB SPL input
level.
In addition to the above recording specifications, when an application has started
recording an audio stream using the
android.media.MediaRecorder.AudioSource.VOICE_RECOGNITION audio source:
Noise reduction processing, if present, MUST be disabled.
Automatic gain control, if present, MUST be disabled.
Note: while some of the requirements outlined above are stated as "SHOULD" for
Android 4.1, the Compatibility Definition for a future version is planned to change these
to "MUST". That is, these requirements are optional in Android 4.1 but will be
required by a future version. Existing and new devices that run Android 4.1 are very
strongly encouraged to meet these requirements in Android 4.1 , or they wil not
be able to attain Android compatibility when upgraded to the future version.
5.4. Audio Latency
Audio latency is broadly defined as the interval between when an application requests
an audio playback or record operation, and when the device implementation actual y
begins the operation. Many classes of applications rely on short latencies, to achieve
real-time effects such sound effects or VOIP communication. Device implementations
that include microphone hardware and declare android.hardware.microphone
SHOULD meet al audio latency requirements outlined in this section. See Section 7
for details on the conditions under which microphone hardware may be omitted by
device implementations.
For the purposes of this section:
"cold output latency" is defined to be the interval between when an application
requests audio playback and when sound begins playing, when the audio system
has been idle and powered down prior to the request
"warm output latency" is defined to be the interval between when an application
requests audio playback and when sound begins playing, when the audio system
has been recently used but is currently idle (that is, silent)
"continuous output latency" is defined to be the interval between when an
application issues a sample to be played and when the speaker physical y plays
the corresponding sound, while the device is currently playing back audio
"cold input latency" is defined to be the interval between when an application
requests audio recording and when the first sample is delivered to the
application via its cal back, when the audio system and microphone has been
idle and powered down prior to the request
"continuous input latency" is defined to be when an ambient sound occurs and
when the sample corresponding to that sound is delivered to a recording
application via its cal back, while the device is in recording mode
Using the above definitions, device implementations SHOULD exhibit each of these
properties:
cold output latency of 100 mil iseconds or less
warm output latency of 10 mil iseconds or less
continuous output latency of 45 mil iseconds or less
cold input latency of 100 mil iseconds or less
continuous input latency of 50 mil iseconds or less
Note: while the requirements outlined above are stated as "SHOULD" for Android 4.1,
the Compatibility Definition for a future version is planned to change these to "MUST".
That is, these requirements are optional in Android 4.1 but will be required by a future
version. Existing and new devices that run Android 4.1 are very strongly
encouraged to meet these requirements in Android 4.1 , or they wil not be able to
attain Android compatibility when upgraded to the future version.
If a device implementation meets the requirements of this section, it MAY report
support for low-latency audio, by reporting the feature "android.hardware.audio.low-
latency" via the android.content.pm.PackageManager class. [Re sources, 37]
Conversely, if the device implementation does not meet these requirements it MUST
NOT report support for low-latency audio.
5.5. Network Protocols
Devices MUST support the media network protocols for audio and video playback as
specified in the Android SDK documentation [Resources, 58]. Specifical y, devices
MUST support the fol owing media network proto cols:
RTSP (RTP, SDP)
HTTP(S) progressive streaming
HTTP(S) Live Streaming draft protocol, Version 3 [Resources, 59]
6. Developer Tool Compatibility
Device implementations MUST support the Android Developer Tools provided in the
Android SDK. Specifical y, Android-compatible devices MUST be compatible with:
Android Debug Bridge (known as adb) [Resources, 33]
Device implementations MUST support al adb functions as doc umented in the
Android SDK. The device-side adb daemon MUST be inactive by default, and
there MUST be a user-accessible mechanism to turn on the Android Debug
Bridge.
Dalvik Debug Monitor Service (known as ddms) [Resources, 33]
Device implementations MUST support al ddms features as documented in the
Android SDK. As ddms uses adb, support for ddms SHOULD be inactive by
default, but MUST be supported whenever the user has activated the Android
Debug Bridge, as above.
Monkey [Resources, 36]
Device implementations MUST include the Monkey framework, and make it
available f or applications to use.
Most Linux-based systems and Apple Macintosh systems recognize Android devices
using the standard Android SDK tools, without additional support; however Microsoft
Windows systems typical y require a driver for new Android devices. (For instance,
new vendor IDs and sometimes new device IDs require custom USB drivers for
Windows systems.) If a device implementation is unrecognized by the adb tool as
provided in the standard Android SDK, device implementers MUST provide Windows
drivers al owing developers to connect to the device using the adb protocol. These
drivers MUST be provided for Windows XP, Windows Vista, and Windows 7, in both
32-bit and 64-bit versions.
7. Hardware Compatibility
If a device includes a particular hardware component that has a corresponding API for
third-party developers, the device implementation MUST implement that API as
described in the Android SDK documentation. If an API in the SDK interacts with a
hardware component that is stated to be optional and the device implementation does
not possess that component:
complete class definitions (as documented by the SDK) for the component's
APIs MUST stil be present
the API's behaviors MUST be implemented as no-ops in some reasonable
fashion
API methods MUST return nul values where permitted by the SDK
documentation
API methods MUST return no-op implementations of classes where nul values
are not permitted by the SDK documentation
API methods MUST NOT throw exceptions not documented by the SDK
documentation
A typical example of a scenario where these requirements apply is the telephony API:
even on non-phone devices, these APIs must be implemented as reasonable no-ops.
Device implementations MUST accurately report accurate hardware configuration
information via the getSystemAvailableFeatures() and hasSystemFeature(String)
methods on the android.content.pm.PackageManager class. [Re sources, 37]
7.1. Display and Graphics
Android 4.1 includes facilities that automatical y adjust application assets and UI
layouts appropriately for the device, to ensure that third-party applications run wel on a
variety of hardware configurations [Resources, 38]. Devices MUST properly implement
these APIs and behaviors, as detailed in this section.
The units referenced by the requirements in this section are defined as fol ows:
"Physical diagonal size" is the distance in inches between two opposing corners
of the il uminated portion of the display.
"dpi" (meaning "dots per inch") is the number of pixels encompassed by a linear
horizontal or vertical span of 1". Where dpi values are listed, both horizontal and
vertical dpi must fal within the range.
"Aspect ratio" is the ratio of the longer dimension of the screen to the shorter
dimension. For example, a display of 480x854 pixels would be 854 / 480 =
1.779, or roughly "16:9".
A "density-independent pixel" or ("dp") is the virtual pixel unit normalized to a 160
dpi screen, calculated as: pixels = dps * (density / 160).
7.1.1. Screen Configuration
Screen Size
The Android UI framework supports a variety of different screen sizes, and al ows
applications to query the device screen size (aka "screen layout") via
android.content.res.Configuration.screenLayout with the
SCREENLAYOUT_SIZE_MASK. Device implementations MUST report the correct screen
size as defined in the Android SDK documentation [Resources, 38] and determined by
the upstream Android platform. Specifical y, device implementations must report the
correct screen size according to the fol owing logical d ensity-independe nt pixel (dp)
screen dimensions.
Devices MUST have screen sizes of at least 426 dp x 320 dp ('smal ')
Devices that report screen size 'normal' MUST have screen sizes of at least 480
dp x 320 dp
Devices that report screen size 'large' MUST have screen sizes of at least 640
dp x 480 dp
Devices that report screen size 'xlarge' MUST have screen sizes of at least 960
dp x 720 dp
In addition, devices MUST have screen sizes of at least 2.5 inches in physical diagonal
size.
Devices MUST NOT change their reported screen size at any time.
Applications optional y indicate which screen sizes they support via the <supports-
screens> attribute in the AndroidManifest.xml file. Device implementations MUST
correctly honor applications' stated support for smal , normal, large, and xlarge
screens, as described in the Android SDK documentation.
Screen Aspect Ratio
The aspect ratio MUST be between 1.3333 (4:3) and 1.85 (16:9).
Screen Density
The Android UI framework defines a set of standard logical densities to help
application developers target application resources. Device implementations MUST
report one of the fol owing logical Android framework densities through the
android.util.DisplayMetrics APIs, and MUST execute applications at this standard
density.
120 dpi, known as 'ldpi'
160 dpi, known as 'mdpi'
213 dpi, known as 'tvdpi'
240 dpi, known as 'hdpi'
320 dpi, known as 'xhdpi'
480 dpi, known as 'xxhdpi'
Device implementations SHOULD define the standard Android framework density that
is numerical y closest to the physical density of the screen, unless that logical density
is numerical y closest to the physical density of the screen, unless that logical density
pushes the reported screen size below the minimum supported. If the standard Android
framework density that is numerical y closest to the physical density results in a screen
size that is smal er than the smal est supported compatible screen size (320 dp width),
device implementations SHOULD report the next lowest standard Android framework
density.
7.1.2. Display Metrics
Device implementations MUST report correct values for al display metrics defined in
android.util.DisplayMetrics [Resources, 39].
7.1.3. Screen Orientation
Devices MUST support dynamic orientation by applications to either portrait or
landscape screen orientation. That is, the device must respect the application's
request for a specific screen orientation. Device implementations MAY select either
portrait or landscape orientation as the default.
Devices MUST report the correct value for the device's current orientation, whenever
queried via the android.content.res.Configuration.orientation,
android.view.Display.getOrientation(), or other APIs.
Devices MUST NOT change the reported screen size or density when changing
orientation.
Devices MUST report which screen orientations they support (
android.hardware.screen.portrait and/or android.hardware.screen.landscape)
and MUST report at least one supported orientation. For example, a device with a
fixed-orientation landscape screen, such as a television or laptop, MUST only report
android.hardware.screen.landscape.
7.1.4. 2D and 3D Graphics Acceleration
Device implementations MUST support both OpenGL ES 1.0 and 2.0, as embodied
and detailed in the Android SDK documentations. Device implementations MUST also
support Android Renderscript, as detailed in the Android SDK documentation
[Resources, 8].
Device impleme ntations MUST also correctly identify themselves as supporting
OpenGL ES 1.0 and 2.0. That is:
The managed APIs (such as via the GLES10.getString() method) MUST report
support for OpenGL ES 1.0 and 2.0
The native C/C++ OpenGL APIs (that is, those available to apps via
libGLES_v1CM.so, libGLES_v2.so, or libEGL.so) MUST report support for
OpenGL ES 1.0 and 2.0.
Device implementations MAY implement any desired OpenGL ES extensions.
However, device implementations MUST report via the OpenGL ES managed and
native APIs al extension strings that they do support, and conversely MUST NOT report
extension strings that they do not support.
Note that Android 4.1 includes support for applications to optional y specify that they
require specific OpenGL texture compression formats. These formats are typical y
vendor-specific. Device implementations are not required by Android 4.1 to implement
any specific texture compression format. However, they SHOULD accurately report any
texture compression formats that they do support, via the getString() method in the
OpenGL API.
Android 4.1 includes a mechanism for applications to declare that they wanted to
enable hardware acceleration for 2D graphics at the Application, Activity, Window or
View level through the use of a manifest tag android:hardwareAccelerated or direct
API cal s [Resources, 9].
In Android 4.1, device implementations MUST enable hardware acceleration by
default, and MUST disable hardware acceleration if the developer so requests by
setting android:hardwareAccelerated="false" or disabling hardware acceleration
directly through the Android View APIs.
In addition, device implementations MUST exhibit behavior consistent with the Android
SDK documentation on hardware acceleration [Resources, 9].
Android 4.1 includes a TextureView object that lets developers directly integrate
hardware-accelerated OpenGL ES textures as rendering targets in a UI hierarchy.
Device implementations MUST support the Textur eView API, and MUST exhibit
consistent behavior with the upstream Android implementation.
7.1.5. Legacy Application Compatibility Mode
Android 4.1 specifies a "compatibility mode" in which the framework operates in an
'normal' screen size equivalent (320dp width) mode for the benefit of legacy
applications not developed for old versions of Android that pre-date screen-size
independence. Device implementations MUST include support for legacy application
compatibility mode as implemented by the upstream Android open source code. That
is, device implementations MUST NOT alter the triggers or thresholds at which
compatibility mode is activated, and MUST NOT alter the behavior of the compatibility
mode itself.
7.1.6. Screen Types
Device implementation screens are classified as one of two types:
Fixed-pixel display implementations: the screen is a single panel that supports
only a single pixel width and height. Typical y the screen is physical y integrated
with the device. Examples include mobile phones, tablets, and so on.
Variable-pixel display implementations: the device implementation either has no
embedded screen and includes a video output port such as VGA, HDMI or a
wireless port for display, or has an embedded screen that can change pixel
dimensions. Examples include televisions, set-top boxes, and so on.
Fixed-Pixel Device Implementations
Fixed-pixel device implementations MAY use screens of any pixel dimensions,
provided that they meet the requirements defined this Compatibility Definition.
Fixed-pixel implementations MAY include a video output port for use with an external
display. However, if that display is ever used for running apps, the device MUST meet
the fol owing requirements:
The device MUST report the same screen configuration and display metrics, as
detailed in Sections 7.1.1 and 7.1.2, as the fixed-pixel display.
The device MUST report the same logical density as the fixed-pixel display.
The device MUST report screen dimensions that are the same as, or very close
to, the fixed-pixel display.
For example, a tablet that is 7" diagonal size with a 1024x600 pixel resolution is
considered a fixed-pixel large mdpi display implementation. If it contains a video
output port that displays at 720p or 1080p, the device implementation MUST scale the
output so that applications are only executed in a large mdpi window, regardless of
whether the fixed-pixel display or video output port is in use.
Variable-Pixel Device Implementations
Variable-pixel device implementations MUST support one or both of 1280x720, or
1920x1080 (that is, 720p or 1080p). Device implementations with variable-pixel
displays MUST NOT support any other screen configuration or mode. Device
implementations with variable-pixel screens MAY change screen configuration or
mode at runtime or boot-time. For example, a user of a set-top box may replace a
720p display with a 1080p display, and the device implementation may adjust
accordingly.
Additional y, variable-pixel device implementations MUST report the fol owing
configuration buckets for these pixel dimensions:
1280x720 (also known as 720p): 'large' screen size, 'tvdpi' (213 dpi) density
1920x1080 (also known as 1080p): 'large' screen size, 'xhdpi' (320 dpi) density
For clarity, device implementations with variable pixel dimensions are restricted to
720p or 1080p in Android 4.1, and MUST be configured to report screen size and
density buckets as noted above.
7.1.7. Screen Technology
The Android platform includes APIs that al ow applications to render rich graphics to
the display. Devices MUST support al of these APIs as defined by the Android SDK
unless specifical y al owed in this document. Specifical y:
Devices MUST support displays capable of rendering 16-bit color graphics and
SHOULD support displays capable of 24-bit color graphics.
Devices MUST support displays capable of rendering animations.
The display technology used MUST have a pixel aspect ratio (PAR) between 0.9
and 1.1. That is, the pixel aspect ratio MUST be near square (1.0) with a 10%
tolerance.
7.2. Input Devices
7.2.1. Keyboard
Device implementations:
MUST include support for the Input Management Framework (which al ows third
party developers to create Input Management Engines - ie soft keyboard) as
detailed at http://developer.android.com
MUST provide at least one soft keyboard implementation (regardless of whether
a hard keyboard is present)
MAY include additional soft keyboard implementations
MAY include a hardware keyboard
MUST NOT include a hardware keyboard that does not match one of the formats
specified in android.content.res.Configuration.keyboard [Resources, 40]
(that is, QWERTY, or 12-key)
7.2.2. Non-touch Navigation
Device implementations:
MAY omit a non-touch navigation option (that is, may omit a trackbal , d-pad, or
wheel)
MUST report the correct value for
android.content.res.Configuration.navigation [Resources, 40]
MUST provide a reasonable alternative user interface m echanism for the
selection and editing of text, compatible with Input Management Engines. The
upstream Android open source software includes a selection mechanism
suitable for use with devices that lack non-touch navigation inputs.
7.2.3. Navigation keys
The Home, Menu and Back functions are essential to the Android navigation
paradigm. Device implementations MUST make these functions available to the user
at al times when running applications. These functions MAY be implemented via
dedicated physical buttons (such as mechanical or capacitive touch buttons), or MAY
be implemented using dedicated software keys, gestures, touch panel, etc. Android
4.1 supports both implementations.
Android 4.1 introduces support for assist action [Resources, 63]. Device
implementations MUST make the assist action available to the user at al times when
running applications. This function MAY be impleme nted via hardwa re or software
keys.
Device implementations MAY use a distinct portion of the screen to display the
navigation keys, but if so, MUST meet these requirements:
Device implementation navigation keys MUST use a distinct portion of the
screen, not available to applications, and MUST NOT obscure or otherwise
interfere with the portion of the screen available to applications.
Device implementations MUST make available a portion of the display to
applications that meets the requirements defined in Section 7.1.1.
Device implementations MUST display the navigation keys when applications do
not specify a system UI mode, or specify SYSTEM_UI_FLAG_VISIBLE.
Device implementations MUST present the navigation keys in an unob trusive
"low profile" (eg. dimmed) mode when applications specify
SYSTEM_UI_FLAG_LOW_PROFILE.
Device implementations MUST hide the navigation keys when applications
specify SYSTEM_UI_FLAG_HIDE_NAVIGATION.
Device implementation MUST present a Menu key to applications when
targetSdkVersion <= 10 and SHOULD NOT present a Menu key when the
targetSdkVersion > 10.
Device implementations MUST make available a portion of the display to
applications that meets the requirements defined in Section 7.1.1.
7.2.4. Touchscreen input
Device implementations SHOULD have a pointer input syste m of some kind (either
mouse-like, or touch). However, if a device implementation does not support a pointer
input system, it MUST NOT report the android.hardware.touchscreen or
android.hardware.faketouch feature constant. Device implementations that do
include a pointer input system:
SHOULD support ful y independently tracked pointers, if the device input system
supports multiple pointers
MUST report the value of android.content.res.Configuration.touchscreen
[ Resources, 40] c orresponding to the type of the specific touchscreen on the
device
Android 4.0 includes support for a variety of touch screens, touch pads, and fake touch
input devices. Touch screen based device implementations are associated with a
display [Resources, 71] such that the user has the impression of directly manipulating
items on screen. Since the user is directly touching the screen, the system does not
require any additional affordances to indicate the objects being manipulated. In
contrast, a fake touch interface provides a user input system that approximates a
subset of touchscreen capabilities. For example, a mouse or remote control that drives
an on-screen cursor approximates touch, but requires the user to first point or focus
then click. Numerous input devices like the mouse, trackpad, gyro-based air mouse,
gyro-pointer, joystick, and multi-touch trackpad can support fake touch interactions.
Android 4.0 includes the feature constant android.hardware.faketouch, which
corresponds to a high-fidelity non-touch (that is, pointer-based) input device such as a
mouse or trackpad that can adequately emulate touch-based input (including basic
gesture support), and indicates that the device supports an emulated subset of
touchscreen functionality. Device implementations that declare the fake touch feature
MUST meet the fake touch requirements in Section 7.2.5.
Device implementations MUST report the correct feature corresponding to the type of
input used. Device implementations that include a touchscreen (single-touch or better)
MUST report the platform feature constant android.hardware.touchscreen. Device
implementations that report the platform feature constant
android.hardware.touchscreen MUST also report the platform feature constant
android.hardware.faketouch. Device implementations that do not include a
touchscreen (and rely on a pointer device only) MUST NOT report any touchscreen
feature, and MUST report only android.hardware.faketouch if they meet the fake
touch requirements in Section 7.2.5.
7.2.5. Fake touch inp ut
Device implementations that declare support for android.hardware.faketouch
MUST report the absolute X and Y screen positions of the pointer location and
display a visual pointer on the screen[Resources, 70]
MUST report touch event with the action code [Resources, 70] that specifies the
state change that occurs on the pointer g oing down or up on the screen
[Resources, 70]
MUST support pointer down and up on an object on the screen, which al ows
u sers to emulate tap on an object on the screen
MUST support pointer down, pointer up, pointer down then pointer up in the same
place on an object on the screen within a time threshold, which al ows users to
emulate double tap on an object on the screen [Resources, 70]
MUST support pointer down on an arbitrary point on the screen, pointer move to
any other arbitrary point on the screen, fol owed by a pointer up , which al ows
users to emulate a touch drag
MUST support pointer down then al ow users to quickly move the object to a
different position on the screen and then pointer up on the screen, which al ows
users to fling an object on the screen
Devices that declare support for android.hardware.faketouch.multitouch.distinct
MUST meet the requirements for faketouch above, and MUST also support distinct
tracking of two or more independent pointer inputs.
7.2.6. Microphone
Device implementations MAY omit a microphone. However, if a device implementation
omits a microphone, it MUST NOT report the android.hardware.microphone feature
constant, and must implement the audio recording API as no-ops, per Section 7.
Conversely, device implementations that do possess a microphone:
MUST report the android.hardware.microphone feature constant
SHOULD meet the audio quality requirements in Section 5.4
SHOULD meet the audio latency requirements in Section 5.5
7.3. Sensors
Android 4.1 includes APIs for accessing a variety of sensor types. Devices
implementations general y MAY omit these sensors, as provided for in the fol owing
subsections. If a device includes a particular sensor type that has a corresponding API
for third-party developers, the device implementation MUST implement that API as
described in the Android SDK documentation. For example, device implementations:
MUST accurately report the presence or absence of sensors per the
android.content.pm.PackageManager class. [Re sources, 37]
MUST return an accurate list of supported sensors via the
SensorManager.getSensorList() and similar methods
MUST behave reasonably for al other sensor APIs (for example, by returning true
or false as appropriate when applications attempt to register listeners, not cal ing
sensor listeners when the corresponding sensors are not present; etc.)
MUST report al sensor measurements using the relevant International System of
Units (ie metric) values for each sensor type as defined in the Android SDK
documentation [Resources, 41]
The list above is not comprehensive; the documented behavior of the Android SDK is
to be considered authoritative.
Some sensor types are synthetic, meaning they can be derived from data provided by
one or more other sensors. (Examples include the orientation sensor, and the linear
acceleration sensor.) Device implementations SHOULD implement these sensor
types, when they include the prerequisite physical sensors.
The Android 4.1 APIs introduce a notion of a "streaming" sensor, which is one that
returns data continuously, rather than only when the data changes. Device
implementations MUST continuously provide periodic data samples for any API
indicated by the Android 4.1 SDK documentation to be a streaming sensor.
7.3.1. Accelerometer
Device implementations SHOULD include a 3-axis accelerometer. If a device
implementation does include a 3-axis accelerometer, it:
SHOULD be able to deliver events at 120 Hz or greater. Note that while the
accelerometer frequency above is stated as "SHOULD" for Android 4.1, the
Compatibility Definition for a future version is planned to change these to
"MUST". That is, these standards are optional in Android 4.1 but will be
required in future versions. Existing and new devices that run Android 4.1 are
very strongly encouraged to meet these requirements in Android 4.1 so
they wil be able to upgrade to the future platform releases
MUST comply with the Android sensor coordinate system as detailed in the
Android APIs (see [Resources, 41])
MUST be capable of measuring from freefal up to twice gravity (2g) or more on
any three-dimension al vector
MUST have 8-bits of accuracy or more
MUST have a standard deviation no greater than 0.05 m/s^2
7.3.2. Magnetometer
Device implementations SHOULD include a 3-axis magnetometer (ie compass.) If a
device does include a 3-axis magnetometer, it:
MUST be able to deliver events at 10 Hz or greater
MUST comply with the Android sensor coordinate system as detailed in the
Android APIs (see [Resources, 41]).
MUST be capable of sampling a range of field strengths adequate to cover the
geomagnetic field
MUST have 8-bits of accuracy or mor e
MUST have a standard deviation no greater than 0.5 µT
7.3.3. GPS
Device implementations SHOULD include a GPS receiver. If a device implementation
does include a GPS receiver, it SHOULD include some form of "assisted GPS"
technique to minimize GPS lock-on time.
7.3.4. Gyroscope
Device implementations SHOULD include a gyroscope (ie angular change sensor.)
Devices SHOULD NOT include a gyroscope sensor unless a 3-axis accelerometer is
also included. If a device implementation includes a gyroscope, it:
MUST be temperature compensated
MUST be capable of measuring orientation changes up to 5.5*Pi
radians/second (that is, approximately 1,000 degrees per second)
SHOULD be able to deliver events at 200 Hz or greater. Note that while the
gyroscope frequency above is stated as "SHOULD" for Android 4.1, the
Compatibility Definition for a future version is planned to change these to
"MUST". That is, these standards are optional in Android 4.1 but will be
required in future versions. Existing and new devices that run Android 4.1 are
very strongly encouraged to meet these requirements in Android 4.1 so
they wil be able to upgrade to the future platform releases
MUST have 12-bits of accuracy or more
MUST have a variance no greater than 1e-7 rad^2 / s^2 per Hz (variance per Hz,
or rad^2 / s). The variance is al owed to vary with the sampling rate, but must be
constrained by this value. In other words, if you measure the variance of the gyro
at 1 Hz sampling rate it should be no greater than 1e-7 rad^2/s^2.
MUST have timestamps as close to when the hardware event happened as
possible. The constant latency must be removed.
7.3.5. Barometer
Device implementations MAY include a barometer (ie ambient air pressure sensor.) If
a device implementation includes a barometer, it:
MUST be able to deliver events at 5 Hz or greater
MUST have adequate precision to enable estimating altitude
MUST be temperature compensated
7.3.7. Thermometer
Device implementations MAY but SHOULD NOT include a thermometer (ie
temperature sensor.) If a device implementation does include a thermometer, it MUST
measure the temperature of the device CPU. It MUST NOT measure any other
temperature. (Note that this sensor type is deprecated in the Android 4.1 APIs.)
7.3.7. Photometer
Device implementations MAY include a photometer (ie ambient light sensor.)
7.3.8. Proximity Sensor
Device implementations MAY include a proximity sensor. If a device implementation
does include a proximity sensor, it MUST measure the proximity of an object in the
same direction as the screen. That is, the proximity sensor MUST be oriented to detect
objects close to the screen, as the primary intent of this sensor type is to detect a
phone in use by the user. If a device implementation includes a proximity sensor with
any other orientation, it MUST NOT be accessible through this API. If a device
implementation has a proximity sensor, it MUST be have 1-bit of accuracy or more.
7.4. Data Connectivity
7.4.1. Telephony
"Telephony" as used by the Android 4.1 APIs and this document refers specifical y to
hardware related to placing voice cal s and sending SMS messages via a GSM or
CDMA network. While these voice cal s may or may not be packet-switched, they are
for the purposes of Android 4.1 considered independent of any data connectivity that
may be implemented using the same network. In other words, the Android "telephony"
functionality and APIs refer specifical y to voice cal s and SMS; for instance, device
implementations that cannot place cal s or send/receive SMS messages MUST NOT
report the "android.hardware.telephony" feature or any sub-features, regardless of
whether they use a cel ular network for data connectivity.
Android 4.1 MAY be used on devices that do not include telephony hardware. That is,
Android 4.1 is compatible with devices that are not phones. However, if a device
implementation does include GSM or CDMA telephony, it MUST implement ful support
for the API for that technology. Device implementations that do not include telephony
hardware MUST implement the ful APIs as no-ops.
7.4.2. IEEE 802.11 (WiFi)
Android 4.1 device implementations SHOULD include support for one or more forms
of 802.11 (b/g/a/n, etc.) If a device implementation does include support for 802.11, it
MUST implement the corresponding Android API.
Device implementations MUST implement the multicast API as described in the SDK
documentation [ Resources, 62]. D evice implementations that do include Wifi support
MUST support multicast DNS (mDNS). Device implementations MUST not filter mDNS
packets (224.0.0.251) at any time of operation including when the screen is not in an
active state.
7.4.2.1. WiFi Direct
Device implementations SHOULD include support for Wifi direct (Wifi peer-to-peer). If
a device implementation does include support for Wifi direct, it MUST implement the
corresponding Android API as described in the SDK documentation [Resources, 68]. If
a device implementation includes support for Wifi direct, then it:
MUST support regular Wifi operation
SHOULD support concurrent wifi and wifi Direct operation
7.4.3. Bluetooth
Device implementations SHOULD include a Bluetooth transceiver. Device
implementations that do include a Bluetooth transceiver MUST enable the RFCOMM-
based Bluetooth API as described in the SDK documentation [Resources, 42]. Device
implementations SHOULD implement relevant Bluetooth profiles, such as A2DP,
AVRCP, OBEX, etc. as appropriate for the device.
The Compatibility Test Suite includes cases that cover basic operation of the Android
RFCOMM Bluetooth API. However, since Bluetooth is a communications protocol
between devices, it cannot be ful y tested by unit tests running on a single device.
Consequently, device implementations MUST also pass the human-driven Bluetooth
test procedure described in Appendix A.
7.4.4. Near-Field Communications
Device implementations SHOULD include a transceiver and related hardware for
Near-Field Communications (NFC). If a device implementation does include NFC
hardware, then it:
MUST report the android.hardware.nfc feature from the
android.content.pm.PackageManager.hasSystemFeature() method.
[Resources, 37]
MUST be capable of reading and writing NDEF messages via the fol owing NFC
s tandards:
MUST be capable of acting as an NFC Forum reader/writer (as defined by
the NFC Forum technical specification NFCForum-TS-DigitalProtocol-1.0)
via the fol owing NFC standards:
NfcA (ISO14443-3A)
NfcB (ISO14443-3B)
NfcF (JIS 6319-4)
IsoDep (ISO 14443-4)
NFC Forum Tag Types 1, 2, 3, 4 (defined by the NFC Forum)
SHOULD be capable of reading and writing NDEF messages via the fol owing
NFC standards. Note that while the NFC standards below are stated as
"SHOULD" for Android 4.1, the Compatibility Definition for a future version is
planned to change these to "MUST". That is, these standards are optional in
Android 4.1 but will be required in future versions. Existing and new devices
that run Android 4.1 are very strongly encouraged to meet these
requirements in Android 4.1 so they wil be able to upgrade to the future
platform releases.
NfcV (ISO 15693)
MUST be capable of transmitting and receiving data via the fol owing peer-to-
peer standards and protocols:
ISO 18092
LLCP 1.0 (defined by the NFC Forum)
SDP 1.0 (defined by the NFC Forum)
NDEF Push Protocol [Resources, 43]
SNEP 1.0 (defined by the NFC Forum)
MUST include support for Android Beam [Resources, 65]:
MUST implement the S NEP default serv er. Valid NDEF messages
received by the default SNEP server MUST be dispatched to applications
using the android.nfc.ACTION_NDEF_DISCOVERED intent. Disabling
Android Beam in settings MUST NOT disable dispatch of incoming NDEF
message.
Device implementations MUST honor the
android.settings.NFCSHARING_SETTINGS intent to show NFC sharing
settings [R esources, 67].
MUST implement the NPP server. Messages received by the NPP server
MUST be processed the same way as the SNEP default server.
MUST implement a SNEP client and attempt to send outbound P2P NDEF
to the default SNEP server when Android Beam is enabled. If no default
SNEP server is found then the client MUST attempt to send to an NPP
server.
MUST al ow foreground activities to set the outbound P2P NDEF message
using android.nfc.NfcAdapter.setNdefPushMessage, and
android.nfc.NfcAdapter.setNdefPushMessageCal back, and
android.nfc.NfcAdapter.enableForegroundNdefPush.
SHOULD use a gesture or on-screen confirmation, such as 'Touch to
Beam', before sending outbound P2P NDEF messages.
SHOULD enable Android Beam by default
MUST support NFC Connection handover to Bluetooth when the device
supports Bluetooth Object Push Profile. Device implementations must
support connection handover to Bluetooth when using
android.nfc.NfcAdapter.setBeamPushUris, by implementing the
"Connection Handover version 1.2" [Resources, 60] and "Bluetooth Secure
Simple Pairing Using NFC version 1.0" [Resources, 61 ] specs from the
NFC Forum. Such an implementation SHO ULD use SNEP G ET requests
for exchanging the handover request / select records over NFC, and it
MUST use the Bluetooth Object Push Profile for the actual Bluetooth data
transfer.
MUST pol for al supported technologies while in NFC discovery mode.
SHOULD be in NFC discovery mode while the device is awake with the screen
active and the lock-screen unlocked.
(Note that publicly available links are not available for the JIS, ISO, and NFC Forum
specifications cited above.)
Additional y, device implementations MAY include reader/writer support for the
fol owing MIFARE technologies.
MIFARE Classic (NXP MF1S503x [Resources, 44], MF1S703x [Resources, 44])
MIFARE Ultralight (NXP MF0ICU1 [Resources, 46], MF0ICU2 [Resources, 46])
NDEF on MIFARE Classic (NXP AN1 30511 [Resourc es, 48], AN13 0411
[Resources, 49])
Note th at Android 4.1 in cludes APIs for these MIFARE types. If a device
implementation supports MIFARE in the reader/writer role, it:
MUST implement the corresponding Android APIs as documented by the
Android SDK
MUST report the feature com.nxp.mifare from the
android.content.pm.PackageManager.hasSystemFeature() method.
[Resources, 37] Note that this is not a standard Android feature, and as such
does not appear as a constant on the PackageManager class.
MUST NOT imple ment the corresponding Android APIs nor report the
com.nxp.mifare feature unless it also implements general NFC support as
described in this section
If a device implementation does not include NFC hardware, it MUST NOT declare the
android.hardware.nfc feature from the
android.content.pm.PackageManager.hasSystemFeature() method [Resources, 37],
and MUST implement the Android 4.1 NFC API as a no-op.
As the classes android.nfc.NdefMessage and android.nfc.NdefRecord r epresent a
protocol-independent data representation format, device implementations MUST
implement these APIs even if they do not include support for NFC or declare the
android.hardware.nfc feature.
7.4.5. Minimum Network Capability
Device implementations MUST include support for one or more forms of data
networking. Specifical y, device implementations MUST include support for at least one
data standard capable of 200Kbit/sec or greater. Examples of technologies that
satisfy this requirement include EDGE, HSPA, EV-DO, 802.11g, Ethernet, etc.
Device implementations where a physical networking standard (such as Ethernet) is
the primary data connection SHOULD also include support for at least one common
wireless data standard, such as 802.11 (WiFi).
Devices MAY implement more than one form of data connectivity.
7.5. Cameras
Device implementations SHOULD include a rear-facing camera, and MAY include a
front-facing camera. A rear-facing camera is a camera located on the side of the
device opposite the display; that is, it images scenes on the far side of the device, like
a traditional camera. A front-facing camera is a camera located on the same side of
the device as the display; that is, a camera typical y used to image the user, such as for
video conferencing and similar applications.
7.5.1. Rear-Facing Camera
Device implementations SHOULD include a rear-facing camera. If a device
implementation includes a rear-facing camera, it:
MUST have a resolution of at least 2 megapixels
SHOULD have either hardware auto-focus, or software auto-focus implemented
in the camera driver (transparent to application software)
MAY have fixed-focus or EDOF (extended depth of field) hardware
MAY include a flash. If the Camera includes a flash, the flash lamp MUST NOT be
lit while an android.hardware.Camera.PreviewCal back instance has been
registered on a Camera preview surface, unless the application has explicitly
enabled the flash by enabling the FLASH_MODE_AUTO or FLASH_MODE_ON attributes
of a Camera.Parameters object. Note that this constraint does not apply to the
device's built-in system camera application, but only to third-party applications
using Camera.PreviewCallback.
7.5.2. Front-Facing Camera
Device implementations MAY include a front-facing camera. If a device implementation
includes a front-facing camera, it:
MUST have a resolution of at least VGA (that is, 640x480 pixels)
MUST NOT use a front-facing camera as the default for the Camera API. That is,
the camera API in Android 4.1 has specific support for front-facing cameras, and
device implementations MUST NOT configure the API to to treat a front-facing
camera as the default rear-facing camera, even if it is the only camera on the
device.
MAY include features (such as auto-focus, flash, etc.) available to rear-facing
cameras as described in Section 7.5.1.
MUST horizontal y reflect (ie mirror) the stream displayed by an app in a
CameraPreview, as fol ows:
If the device implementation is capable of being rotated by user (such as
automatical y via an accelerometer or manual y via user input), the camera
preview MUST be mirrored horizontal y relative to the device's current
orientation.
If the current application has explicitly requested that the Camera display
be rotated via a cal to the
android.hardware.Camera.setDisplayOrientation() [Resources, 50]
method, the camera preview MUST be mirrored horizontal y relative to the
orientation specified by the application.
Otherwise, the preview MUST be mirrored along the device's default
horizontal axis.
MUST mirror the image displayed by the postview in the same manner as the
camera preview image stream. (If the device implementation does not support
postview, this requirement obviously does not apply.)
MUST NOT mirror the final captured stil image or video streams returned to
application cal backs or committed to media storage
7.5.3. Camera API Behavior
Device implementations MUST implement the fol owing behaviors for the camera-
related APIs, for both front- and rear-facing cameras:
1. If an application has never cal ed
android.hardware.Camera.Parameters.setPreviewFormat(int), then the
device MUST use android.hardware.PixelFormat.YCbCr_420_SP for preview
data provided to application cal backs.
2. If an application registers an android.hardware.Camera.PreviewCallback
instance and the system cal s the onPreviewFrame() method when the preview
format is YCbCr_420_SP, the data in the byte[] passed into onPreviewFrame()
must further be in the NV21 encoding format. That is, NV21 MUST be the default.
3. Device implementations MUST support the YV12 format (as denoted by the
android.graphics.ImageFormat.YV12 constant) for camera previews for both
front- and rear-facing cameras. (The hardware video decoder and camera may
use any native pixel format, but the device implementation MUST support
conversion to YV12.)
Device implementations MUST implement the ful Camera API included in the Android
4.1 SDK documentation [R esources, 51]), r egardless of whether the device includes
hardware autofocus or other capabilities. For instance, cameras that lack autofocus
MUST stil cal any registered android.hardware.Camera.AutoFocusCallback
instances (even though this has no relevance to a non-autofocus camera.) Note that
this does apply to front-facing cameras; for instance, even though most front-facing
cameras do not support autofocus, the API cal backs must stil be "faked" as
described.
Device implementations MUST recognize and honor each parameter name defined as
a constant on the android.hardware.Camera.Parameters class, if the underlying
hardware supports the feature. If the device hardware does not support a feature, the
API must behave as documented. Conversely, Device implementations MUST NOT
honor or recognize string constants passed to the
android.hardware.Camera.setParameters() method other than those documented as
constants on the android.hardware.Camera.Parameters. That is, device
implementations MUST support al standard Camera parameters if the hardware
al ows, and MUST NOT support custom Camera parameter types.
Device implementations MUST broadcast the Camera.ACTION_NEW_PICTURE intent
whenever a new picture is taken by the camera and the entry of the picture has been
added to the media store.
Device implementations MUST broadcast the Camera.ACTION_NEW_VIDEO intent
whenever a new video is recorded by the camera and the entry of the picture has been
added to the media store.
7.5.4. Camera Orientation
Both front- and rear-facing cameras, if present, MUST be oriented so that the long
dimension of the camera aligns with the screen's long dimention. That is, when the
device is held in the landscape orientation, cameras MUST capture images in the
landscape orientation. This applies regardless of the device's natural orientation; that
is, it applies to landscape-primary devices as wel as portrait-primary devices.
7.6. Memory and Storage
7.6.1. Minimum Memory and Storage
Device implementations MUST have at least 340MB of memory available to the kernel
and userspace. The 340MB MUST be in addition to any memory dedicated to
hardware components such as radio, video, and so on that is not under the kernel's
control.
Device implementations MUST have at least 350MB of non-volatile storage available
for application private data. That is, the /data partition MUST be at least 350MB.
The Android APIs include a Download Manager that applications may use to download
data files [Resources, 56]. The device implementation of the Download Manager
MUST be capable of downloading individual files of at least 100MB in size to the
default "cache" location.
7.6.2. Application Shared Storage
Device implementations MUST offer shared storage for applications. The shared
storage provided MUST be at least 1GB in size.
Device implementations MUST be configured with shared storage mounted by default,
"out of the box". If the shared storage is not mounted on the Linux path /sdcard, then
the device MUST include a Linux symbolic link from /sdcard to the actual mount point.
Device implementations MUST enforce as documented the
android.permission.WRITE_EXTERNAL_STORAGE permission on this shared storage.
Shared storage MUST otherwise be writable by any application that obtains that
permission.
Device implementations MAY have hardware for user-accessible removable storage,
such as a Secure Digital card. Alternatively, device implementations MAY al ocate
internal (non-removable) storage as shared storage for apps.
Regardless of the form of shared storage used, device implementations MUST
provide some mechanism to access the contents of shared storage from a host
computer, such as USB mass storage (UMS) or Media Transfer Protocol (MTP).
Device implementations MAY use USB mass storage, but SHOULD use Media
Transfer Protocol. If the device implementation supports Media Transfer Protocol:
The device implementation SHOULD be compatible with the reference Android
MTP host, Android File Transfer [R esources, 57].
The device implementation SHOULD report a USB device class of 0x00.
The device implementation SHOULD report a USB interface name of 'MTP'.
If the device implementation lacks USB ports, it MUST provide a host computer with
access to the contents of shared storage by some other means, such as a network file
system.
It is il ustrative to consider two common examples. If a device implementation includes
an SD card slot to satisfy the shared storage requirement, a FAT-formatted SD card
1GB in size or larger MUST be included with the device as sold to users, and MUST
be mounted by default. Alternatively, if a device implementation uses internal fixed
storage to satisfy this requirement, that storage MUST be 1GB in size or larger and
mounted on /sdcard (or /sdcard MUST be a symbolic link to the physical location if it
is mounted elsewhere.)
Device implementations that include multiple shared storage paths (such as both an
SD card slot and shared internal storage) SHOULD modify the core applications such
as the media scanner and ContentProvider to transparently support files placed in both
locations.
7.7. USB
Device implementations SHOULD include a USB client port, and SHOULD include a
USB host port.
If a device implementation includes a USB client port:
the port MUST be connectable to a USB host with a standard USB-A port
the port SHOULD use the micro USB form factor on the device side. Existing
and new devices that run Android 4.1 are very strongly encouraged to meet
these requirements in Android 4.1 so they wil be able to upgrade to the future
platform releases
the port SHOULD be centered in the middle of an edge. Device implementations
SHOULD either locate the port on the bottom of the device (according to natural
orientation) or enable software screen rotation for al apps (including home
screen), so that the display draws correctly when the device is oriented with the
port at bottom. Existing and new devices that run Android 4.1 are very strongly
encouraged to meet these requirements in Android 4.1 so they wil be able
to upgrade to future platform releases.
if the device has other ports (such as a non-USB charging port) it SHOULD be
on the same edge as the micro-USB port
it MUST al ow a host connected to the device to access the contents of the
shared storage volume using either USB mass storage or Media Transfer
Protocol
it MUST implement the Android Open Accessory API and specification as
documented in the Android SDK documentation, and MUST declare support for
the hardware feature android.hardware.usb.accessory [Resources, 52]
it MUST implement the USB audio class as documented in the Android SDK
documentation [Resources, 66]
it SHOULD implement support for USB battery charging spec ification
[Resources, 64] Existing and new devices that run Android 4.1 are very
strongly encour aged to meet th ese requirements in Android 4.1 so they
wil be able to upgrade to the future platform releases
If a device implementation includes a USB host port:
it MAY use a non-standard port form factor, but if so MUST ship with a cable or
cables adapting the port to standard USB-A
it MUST implement the Android USB host API as documented in the Android
SDK, and MUST declare support for the hardware feature
android.hardware.usb.host [Resources, 53]
Device implementations MUST implement the Android Debug Bridge. If a device
implementation omits a USB client port, it MUST implement the Android Debug Bridge
via local-area network (such as Ethern et or 802.11)
8. Performance Compatibility
Device implementations MUST meet the key performance metrics of an Android 4.1
compatible device defined in the table below:
Metric
Performance Threshold
Comments
The fol owing applications
should launch within the
specified time.
The launch time is measured as the
total time to complete loading the
Browser: less than
default activity for the application,
Application
1300ms
including the time it takes to start the
Launch Time
Contacts: less than
Linux process, load the Android
700ms
package into the Dalvik VM, and cal
Settings: less than
onCreate.
700ms
When multiple applications
have been launched, re-
launching an already-
Simultaneous
running application after it
Applications
has been launched must
take less than the original
launch time.
9. Security Model Compatibility
Device implementations MUST implement a security model consistent with the Android
platform security model as defined in Security and Permissions reference document in
the APIs [Resources, 54] in the Android developer documentation. Device
implementations MUST support instal ation of self-signed applications without
requiring any additional permissions/certificates from any third parties/authorities.
Specifical y, compatible devices MUST support the security mechanisms described in
the fol ow sub-sections.
9.1. Permissions
Device implementations MUST support the Android permissions model as defined in
the Android developer documentation [Resources, 54]. Specifical y, implementations
MUST enforce each permission defined as described in the SDK documentation; no
permissions may be omitted, altered, or i gnored. Impleme ntations MAY add additional
permissions, provided the new permission ID strings are not in the android.*
namespace.
9.2. UID and Process Isolation
Device implementations MUST support the Android application sandbox model, in
which each application runs as a unique Unix-style UID and in a separate process.
Device implementations MUST support running multiple applications as the same
Linux user ID, provided that the applications are properly signed and constructed, as
defined in the Security and Permissions reference [Resources, 54].
9.3. Filesystem Permissions
Device implementations MUST support the Android file access permissions model as
defined in as defined in the Security and Permissions reference [Resources, 54].
9.4. Alternate Execution Environments
Device implementations MAY include runtime environments that execute applications
using some other software or technology than the Dalvik virtual machine or native
code. However, such alternate execution environments MUST NOT compromise the
Android security model or the security of instal ed Android applications, as described
in this section.
Alternate runtimes MUST themselves be Android applications, and abide by the
standard Android security model, as described elsewhere in Section 9.
Alternate runtimes MUST NOT be granted access to resources protected by
permissions not requested in the runtime's AndroidManifest.xml file via the <uses-
permission> mechanism.
Alternate runtimes MUST NOT permit applications to make use of features protected
by Android permissions restricted to system applications.
Alternate runtimes MUST abide by the Android sandbox model. Specifical y:
Alternate runtimes SHOULD instal apps via the PackageManager into separate
Android sandboxes (that is, Linux user IDs, etc.)
Alternate runtimes MAY provide a single Android sandbox shared by al
applications using the alternate runtime
Alternate runtimes and instal ed applications using an alternate runtime MUST
NOT reuse the sandbox of any other app instal ed on the device, except through
the standard Android mechanisms of shared user ID and signing certificate
Alternate runtimes MUST NOT launch with, grant, or be granted access to the
sandboxes corresponding to other Android applications
Alternate runtimes MUST NOT be launched with, be granted, or grant to other
applications any privileges of the superuser (root), or of any other user ID.
The .apk files of alternate runtimes MAY be included in the system image of a device
implementation, but MUST be signed with a key distinct from the key used to sign other
applications included with the device implementation.
When instal ing applications, alternate runtimes MUST obtain user consent for the
Android permissions used by the application. That is, if an application needs to make
use of a device resource for which there is a corresponding Android permission (such
as Camera, GPS, etc.), the alternate runtime MUST inform the user that the application
wil be able to access that resource. If the runtime environment does not record
application capabilities in this manner, the runtime environment MUST list al
permissions held by the runtime itself when instal ing any application using that runtime.
10. Software Compatibility Testing
Device implementations MUST pass al tests described in this section.
However, note that no software test package is ful y comprehensive. For this reason,
device implementers are very strongly encouraged to make the minimum number of
changes as possible to the reference and preferred implementation of Android 4.1
available from the Android Open Source Project. This wil minimize the risk of
introducing bugs that create incompatibilities requiring rework and potential device
updates.
10.1. Compatibility Test Suite
Device implementations MUST pass the Android Compatibility Test Suite (CTS)
[Resources, 2] available from the Android Open Source Project, using the final
shipping software on the device. Additional y, device implementers SHOULD use the
r eference imple mentation in the Android Open Source tree as much as possible, and
MUST ensure compatibility in cases of ambiguity in CTS and for any
reimplementations of parts of the reference source code.
The CTS is designed to be run on an actual device. Like any software, the CTS may
itself contain bugs. The CTS wil be versioned independently of this Compatibility
Definition, and multiple revisions of the CTS may be released for Android 4.1. Device
implementations MUST pass the latest CTS version available at the time the device
software is completed.
10.2. CTS Verifier
Device implementations MUST correctly execute al applicable cases in the CTS
Verifier. The CTS Verifier is included with the Compatibility Test Suite, and is intended
to be run by a human operator to test functionality that cannot be tested by an
automated system, such as correct functioning of a camera and sensors.
The CTS Verifier has tests for many kinds of hardware, including some hardware that
is optional. Device implementations MUST pass al tests for hardware which they
possess; for instance, if a device possesses an accelerometer, it MUST correctly
execute the Accelerometer test case in the CTS Verifier. Test cases for features noted
as optional by this Compatibility Definition Document MAY be skipped or omitted.
Every device and every build MUST correctly run the CTS Verifier, as noted above.
However, since many builds are very similar, device implementers are not expected to
explicitly run the CTS Verifier on builds that differ only in trivial ways. Specifical y,
device implementations that differ from an implementation that has passed the CTS
Verfier only by the set of included locales, branding, etc. MAY omit the CTS Verifier
test.
10.3. Reference Applications
Device implementers MUST test implementation compatibility using the fol owing open
source applications:
The "Apps for Android" applications [Re sources, 55]
Replica Island (available in Android Market)
Each app above MUST launch and behave correctly on the implementation, for the
implementation to be considered compatible.
11. Updatable Software
Device implementations MUST include a mechanism to replace the entirety of the
system software. The mechanism need not perform "live" upgrades - that is, a device
restart MAY be required.
Any method can be used, provided that it can replace the entirety of the software
preinstal ed on the device. For instance, any of the fol owing approaches wil satisfy
this requirement:
Over-the-air (OTA) downloads with offline update via reboot
"Tethered" updates over USB from a host PC
"Offline" updates via a reboot and update from a file on removable storage
The update mechanism used MUST support updates without wiping user data. That is,
the update mechanism MUST preserve application private data and application
shared data. Note that the upstream Android software includes an update mechanism
that satisfies this requirement.
If an error is found in a device implementation after it has been released but within its
reasonable product lifetime that is determined in consultation with the Android
Compatibility Team to affect the compatibility of third-party applications, the device
implementer MUST correct the error via a software update available that can be
applied per the mechanism just described.
12. Contact Us
You can contact the document authors at compatibility@android.com for clarifications
and to bring up any issues that you think the document does not cover.
Appendix A - Bluetooth Test Procedure
The Compatibility Test Suite includes cases that cover basic operation of the Android
RFCOMM Bluetooth API. However, since Bluetooth is a communications protocol
between devices, it cannot be ful y tested by unit tests running on a single device.
Consequently, device implementations MUST also pass the human-operated Bluetooth
test procedure described below.
The test procedure is based on the BluetoothChat sample app included in the Android
open source project tree. The procedure requires two devices:
a candidate device implementation running the software build to be tested
a separate device implementation already known to be compatible, and of a
model from the device implementation being tested - that is, a "known good"
device implementation
The test procedure below refers to these devices as the "candidate" and "known
good" devices, respectively.
Setup and Installation
1. Build BluetoothChat.apk via 'make samples' from an Android source code tree
2. Instal BluetoothChat.apk on the known-good device
3. Instal BluetoothChat.apk on the candidate device
Test Bluetooth Control by Apps
1. Launch BluetoothChat on the candidate device, while Bluetooth is disabled
2. Verify that the candidate device either turns on Bluetooth, or prompts the user
with a dialog to turn on Bluetooth
Test Pairing and Communication
1. Launch the Bluetooth Chat app on both devices
2. Make the known-good device discoverable from within BluetoothChat (using the
Menu)
3. On the candidate device, scan for Bluetooth devices from within BluetoothChat
(using the Menu) and pair with the known-good device
4. Send 10 or more messages from each device, and verify that the other device
receives them correctly
5. Close the BluetoothChat app on both devices by pressing Home
6. Unpair each device from the other, using the device Settings app
Test Pairing and Communication in the Reverse
Direction
1. Launch the Bluetooth Chat app on both devices.
2. Make the candidate device discoverable from within BluetoothChat (using the
Menu).
3. On the known-good device, scan for Bluetooth devices from within BluetoothChat
(using the Menu) and pair with the candidate device.
4. Send 10 or messages from each device, and verify that the other device
receives them correctly.
5. Close the Bluetooth Chat app on both devices by pressing Back repeatedly to
get to the Launcher.
Test Re-Launches
1. Re-launch the Bluetooth Chat app on both devices.
2. Send 10 or messages from each device, and verify that the other device
receives them correctly.
Note: the above tests have some cases which end a test section by using Home, and
some using Back. These tests are not redundant and are not optional: the objective is
to verify that the Bluetooth API and stack works correctly both when Activities are
explicitly terminated (via the user pressing Back, which cal s finish()), and implicitly sent
to background (via the user pressing Home.) Each test sequence MUST be performed
as described.