What happened is that when I move my codes to different lines, and when I CTRL+S, the code automatically get moved to a different line.
What setting in VS Code is this?
That's because you have format on save.
You need to go to VS Code settings and search formatOnSave
and turn it off
check if the "auto format on save" option is on: VSCode: How do you autoformat on save?
you can also go into the dart plugin's preferences in vscode and change the line length at which formatting the code will auto-wrap it. You can make it however long you want. Just go into settings and search "Dart: Line Length"
For me, I went to the dart extension setting, there is an option of Dart: Enable SDK Formatter. It should be the problem I guess because when I disabled it, everything started working fine.
We can directly search for Dart: Enable SDK Formatter in VS Code settings.