我怎么知道什么时候由于方向改变而不是返回/返回而调用onPause（）？

Question

The title says it all. How can I tell when onPause() is being called because of an orientation change instead of the back or home buttons being pressed?

Answer 1

I avoided the problem altogether by doing this instead:

You can use onWindowFocusChanged event instead of onPause. This function is not called when orientation changed.

@Override
public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);
    Log.d(TAG, "FOCUS = " + hasFocus);
    if (!hasFocus) finish();
}

But note: this event is called when activity is still visible (like onPause()), you should use onStop if you want to finish the activity when it is really and fully invisible:

private boolean isInFocus = false;

@Override
public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);
    Log.d(TAG, "FOCUS = " + hasFocus);
    isInFocus = hasFocus;
}

@Override
public void onStop() {
    super.onStop();
    if (!isInFocus) finish();
}

Answer 2

You cannot differentiate how onPause is called. What you could do is, You can override onKeyDown and look for back button and home button key events.

Have a flag that marks back/home button presses and check for this flag in onPause(). If this flag is not set, onPause is called cos of orientation change. However, there is a chance that your app is moved to background due to a phone call or alarm! So maynot be a perfect solution.

The other solution is to keep track of orientation changes in onConfigurationChanged

Answer 3

You probably want onSaveInstanceState instead of onPause

they serve similar function but onSaveInstanceState is not called when the user is backing out of the activity.

Answer 4

http://developer.android.com/reference/android/view/OrientationEventListener.html This should work. Why don't you toast in this.

Answer 5

You can't. Simple as that. You can however measure the time it takes to reach onResume again and if the device was tilted by reading the display configuration.

An interval of 3 seconds is somewhat reasonable, also for slower devices.

Here are the relevant parts that we use:

protected void onCreate() {
  ...
  orientation = getResources().getConfiguration().orientation;
}

protected void onResume() {
  ...
  long time = SystemClock.elapsedRealtime() - pauseTime;
  int o = getResources().getConfiguration().orientation;
  Log.d(TAG, "pauseTime: " + pauseTime + " System: " + SystemClock.elapsedRealtime() + " elapsed pause time: " + time + " orientation now: " + o + " orientation then: " + orientation);
  if (time < 3000 && o != orientation) {
    // device was turned
  }
  orientation = o;
}

protected void onPause() {
  ...
  pauseTime = SystemClock.elapsedRealtime();
}

protected void onSaveInstanceState(final Bundle outState) {
  ...
  outState.putLong(PAUSE_TIME, pauseTime);
  outState.putInt(ORIENTATION, orientation);
}

protected void onRestoreInstanceState(final Bundle savedInstanceState) {
  ...
  pauseTime = savedInstanceState.getLong(PAUSE_TIME, -1);
  orientation = savedInstanceState.getInt(ORIENTATION, -1);
}

The above code is running on about 40k devices and reliably works.