How do I detect if the user has left my app?

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!");  
}

Note: This only works if your target is >= API14

You can also use Application.registerActivityLifecycleCallbacks() and when any activity pauses post a delayed Runnable (that will invoke when user lefts app) to Handler. When activities are created/started/resumed you remove that Runnable from Handler. So when you navigate inside your app you always cancel that Runnable, but if another activity not from your app is activated - the Runnable will be invoked.

I used this to logout user when he lefts my app, here's code for callbacks:

public class MyApplication extends Application implements Application.ActivityLifecycleCallbacks {

    private Handler handler;
    private Runnable runLogout = new Runnable() {
        @Override
        public void run() {
            //logoutUser()
        }
    };

    @Override
    public void onCreate() {
        super.onCreate();

        registerActivityLifecycleCallbacks(this);
        handler = new Handler(getMainLooper());
    }

    @Override
    public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
        handler.removeCallbacks(runLogout);
    }

    @Override
    public void onActivityStarted(Activity activity) {
        handler.removeCallbacks(runLogout);
    }

    @Override
    public void onActivityResumed(Activity activity) {
        handler.removeCallbacks(runLogout);
    }

    @Override
    public void onActivityPaused(Activity activity) {
        handler.postDelayed(runLogout, 1000);
    }

    @Override
    public void onActivityStopped(Activity activity) {

    }

    @Override
    public void onActivitySaveInstanceState(Activity activity, Bundle outState) {

    }

    @Override
    public void onActivityDestroyed(Activity activity) {

    }
}

However, Runnable will run not in the context of activity lifecycle, so to use this in activity you would need to set and check some application-wide flag or broadcast an intent.

Tags:

Android

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