Using FLAG_ACTIVITY_REORDER_TO_FRONT to switch among persistently running UI activities leads to “no window focus” error

Question

My objective is to keep two UI activities alive and to switch back and forth between them at will without having to kill/restart either of them. But there is a serious side

Answer 1

The workaround provided in https://code.google.com/p/android/issues/detail?id=63570#c15 worked pretty well for me to resolve the issue of Activity not getting window focus:

protected void onNewIntent(Intent intent) {
    super.onNewIntent(intent);
    if ((intent.getFlags() | Intent.FLAG_ACTIVITY_REORDER_TO_FRONT) > 0) {
        if (android.os.Build.VERSION.SDK_INT >= 19 && !isTaskRoot()) {
            ActivityManager tasksManager = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
            tasksManager.moveTaskToFront(getTaskId(), ActivityManager.MOVE_TASK_NO_USER_ACTION);
        }
    }
}

This will also need the permission in AndroidManifest.xml

<uses-permission android:name="android.permission.REORDER_TASKS" />

I actually run into this issue in Espresso test getting such error:

java.lang.RuntimeException: Waited for the root of the view hierarchy to have window focus and not be requesting layout for over 10 seconds. If you specified a non default root matcher, it may be picking a root that never takes focus. Otherwise, something is seriously wrong.