Use Analytics in a WebView


Calls to log events or set user properties fired from within a WebView must be forwarded to native code before they can be sent to Google Analytics.

Implement JavaScript handler

The first step in using Google Analytics in a WebView is to create JavaScript functions to forward events and user properties to native code. The following example shows how to do this in a way that is compatible with both Android and Apple native code: 
function logEvent(name, params) {
  if (!name) {
    return;
  }

  if (window.AnalyticsWebInterface) {
    // Call Android interface
    window.AnalyticsWebInterface.logEvent(name, JSON.stringify(params));
  } else if (window.webkit
      && window.webkit.messageHandlers
      && window.webkit.messageHandlers.firebase) {
    // Call iOS interface
    var message = {
      command: 'logEvent',
      name: name,
      parameters: params
    };
    window.webkit.messageHandlers.firebase.postMessage(message);
  } else {
    // No Android or iOS interface found
    console.log("No native APIs found.");
  }
}

function setUserProperty(name, value) {
  if (!name || !value) {
    return;
  }

  if (window.AnalyticsWebInterface) {
    // Call Android interface
    window.AnalyticsWebInterface.setUserProperty(name, value);
  } else if (window.webkit
      && window.webkit.messageHandlers
      && window.webkit.messageHandlers.firebase) {
    // Call iOS interface
    var message = {
      command: 'setUserProperty',
      name: name,
      value: value
   };
    window.webkit.messageHandlers.firebase.postMessage(message);
  } else {
    // No Android or iOS interface found
    console.log("No native APIs found.");
  }
}
index.js

Call the JavaScript handler from your WebView

You can properly log events and set user properties from within a WebView by calling the JavaScript functions that you defined in the previous step. The following example shows how to properly log a purchase event and set a user property as an example: 
function logEventExample() {
   
   // Log an event named "purchase" with parameters
   logEvent("purchase", {
      content_type: "product",
      value: 123,
      currency: "USD",
      quantity: 2,
      items: [{
        item_id: "sample-item-id",
        item_variant: "232323"
      }],
      transaction_id: "1234567"
   });
}

function logUserPropertyExample() {
   // Set a user property named 'favorite_genre'
   setUserProperty("favorite_genre", "comedy")    
}

Implement native interface

To invoke native Apple code from JavaScript, create a message handler class conforming to the WKScriptMessageHandler protocol. You can make Google Analytics calls inside the userContentController:didReceiveScriptMessage: callback:

Swift

Note: This Firebase product is not available on the macOS target. 
func userContentController(_ userContentController: WKUserContentController,
                         didReceive message: WKScriptMessage) {
  guard let body = message.body as? [String: Any] else { return }
  guard let command = body["command"] as? String else { return }
  guard let name = body["name"] as? String else { return }

  if command == "setUserProperty" {
    guard let value = body["value"] as? String else { return }
    Analytics.setUserProperty(value, forName: name)
  } else if command == "logEvent" {
    guard let params = body["parameters"] as? [String: NSObject] else { return }
    Analytics.logEvent(name, parameters: params)
  }
}
ViewController.swift

Objective-C

- (void)userContentController:(WKUserContentController *)userContentController
      didReceiveScriptMessage:(WKScriptMessage *)message {
  if ([message.body[@"command"] isEqual:@"setUserProperty"]) {
    [FIRAnalytics setUserPropertyString:message.body[@"value"] forName:message.body[@"name"]];
  } else if ([message.body[@"command"] isEqual: @"logEvent"]) {
    [FIRAnalytics logEventWithName:message.body[@"name"] parameters:message.body[@"parameters"]];
  }
}
ViewController.m

Finally, add the message handler to the webview's user content controller:

Swift

Note: This Firebase product is not available on the macOS target. 
self.webView.configuration.userContentController.add(self, name: "firebase")
ViewController.swift

Objective-C

Note: This Firebase product is not available on the macOS target. 
[self.webView.configuration.userContentController addScriptMessageHandler:self
                                                                     name:@"firebase"];
ViewController.m

Next Steps

For a fully functional implementation of Google Analytics in a WebView, see the analytics-webview sample.