Android Facebook lock screen notification

Question

On the latest version of Android app Facebook showed lock screen notification feature, like on this screenshot:

Did anyone try to implement this?

I

Answer 1

I think it is probably using the same trick as the Chat heads bubbles for Messenger.

Basically you use this permission "android.permission.SYSTEM_ALERT_WINDOW" to display your views above other apps.

I haven't tried myself but I am pretty sure they used this.

From the docs "Allows an application to open windows using the type TYPE_SYSTEM_ALERT, shown on top of all other applications. " http://developer.android.com/reference/android/Manifest.permission.html#SYSTEM_ALERT_WINDOW

Answer 2

Actually, ferdy182 was/is onto something.

Here's what I got using the android.permission.SYSTEM_ALERT_WINDOW:

So, I couldn't do this with an Activity. It just wouldn't work. I had to implement a Service which added a View using the WindowManager.

One possible workflow would be: a broadcast is received by your BroadcastReceiver => it starts a Service => the Service adds the required view.

Now, the code (the comments explain a few things):

public class MyService extends Service {

    View mView;

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

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

        // instance of WindowManager
        WindowManager mWindowManager = (WindowManager) getSystemService(WINDOW_SERVICE);

        LayoutInflater mInflater = (LayoutInflater) 
                                      getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        // inflate required layout file
        mView = mInflater.inflate(R.layout.abc, null);

        // attach OnClickListener
        mView.findViewById(R.id.some_id).setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // you can fire an Intent accordingly - to deal with the click event
                // stop the service - this also removes `mView` from the window
                // because onDestroy() is called - that's where we remove `mView`
                stopSelf();
            }
        });

        // the LayoutParams for `mView`
        // main attraction here is `TYPE_SYSTEM_ERROR`
        // as you noted above, `TYPE_SYSTEM_ALERT` does not work on the lockscreen
        // `TYPE_SYSTEM_OVERLAY` works very well but is focusable - no click events
        // `TYPE_SYSTEM_ERROR` supports all these requirements
        WindowManager.LayoutParams mLayoutParams = new WindowManager.LayoutParams(
            ViewGroup.LayoutParams.WRAP_CONTENT, 
            ViewGroup.LayoutParams.WRAP_CONTENT, 0, 0,
            WindowManager.LayoutParams.TYPE_SYSTEM_ERROR,
            WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED
                    | WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD
                    | WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
                    | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON, 
                      PixelFormat.RGBA_8888);

        // finally, add the view to window
        mWindowManager.addView(mView, mLayoutParams);
    }

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

        // remove `mView` from the window
        removeViewFromWindow();
    }

    // Removes `mView` from the window
    public void removeNow() {
        if (mView != null) {
            WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
            wm.removeView(mView);
        }
    }
}

And finally, add the permission to your app's manifest:

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