Question

I am developing an Android app and I want to detect when the user exits my app either by clicking the Back button or the Home button.

Also, an event like onInit() would be useful in my scenario, as I just want to have the MyInıt action start at first.

onDestroy() is not called until other apps need more memory.

Answer 1

If your activity is the last in the stack then detecting a back button with onKeyDown would solve 1/2 of this

The home key is a little trickier, there is no absolute method but you could do something like this which works for my simple needs.

The onUserLeaveHint is called according to the documentation when the user clicks the home button OR when something interrupts your application (like an incoming phone call) so to guess which it is you use the onUserInteraction method to stamp the last user interaction time.

Now if that precedes the onUserLeaveHint closely enough you can assume (not guaranteed but has worked for me so far) that the home button was the reason your application is being pushed into the background (exiting)

Not sure what your intent is in catching the home button, anyway here is a simplistic way to do that, I use a 100ms fence around the two events which I have found has always worked for me. NOTE: I have only tested on a handful of phones, like all things in Android your mileage will vary dependent on OS / Hardware (heck even the stuff that’s documented and supposed to work sometimes doesn’t)

long userInteractionTime = 0;

@Override
public void onUserInteraction() {
    userInteractionTime = System.currentTimeMillis();
    super.onUserInteraction();
    Log.i("appname","Interaction");
}

@Override
public void onUserLeaveHint() {
    long uiDelta = (System.currentTimeMillis() - userInteractionTime);

    super.onUserLeaveHint();
    Log.i("bThere","Last User Interaction = "+uiLag);
    if (uiDelta < 100)
        Log.i("appname","Home Key Pressed");    
    else
        Log.i("appname","We are leaving, but will probably be back shortly!");  
}