Draw Overlay in Android (system wide)

Question

Is there a way to draw an overlay window always on top of any android application?

I am using Android x86 port and have system rights.

@Edit: The view below the overlay should receive all events.

Answer 1

It's possible to do that by creating a Service that adds the view in the current WindowManager:

public class OverlayService extends Service {

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

        WindowManager windowManager = (WindowManager) getSystemService(WINDOW_SERVICE);

        View overlay = /* create your overlay here */;

        WindowManager.LayoutParams params = new WindowManager.LayoutParams(
            WindowManager.LayoutParams.WRAP_CONTENT,
            WindowManager.LayoutParams.WRAP_CONTENT,
            WindowManager.LayoutParams.TYPE_SYSTEM_ALERT,
            WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE,
            PixelFormat.TRANSLUCENT);
        windowManager.addView(overlay , params);
    }

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

But you need this extra permission:

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

And then just register the service in the manifest:

<service android:name=".OverlayService" ></service>

and start it:

startService(new Intent(this, OverlayService.class));