Overlay-Bildschirm auf Android

Antwort ist SYSTEM_ALERT_WINDOW, diese geben Ihnen die Fähigkeit zu zeichnen, über jede Sache, die in android, die gleiche Funktion facebook für die Zeichnung seinen chat-heads.

http://developer.android.com/reference/android/Manifest.permission.html#SYSTEM_ALERT_WINDOW

Beispielcode:

    private WindowManager windowManager;
    private ImageView imageView;
   //Get window manager reference

    windowManager = (WindowManager) getSystemService(WINDOW_SERVICE);

    imageView= new ImageView(YOUR_CONTEXT_HERE);
    imageView.setImageResource(R.drawable.android_head);

    //Setup layout parameter
    WindowManager.LayoutParams params = new WindowManager.LayoutParams(
        WindowManager.LayoutParams.WRAP_CONTENT,
        WindowManager.LayoutParams.WRAP_CONTENT,
        WindowManager.LayoutParams.TYPE_PHONE,
        WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
        PixelFormat.TRANSLUCENT);

    params.gravity = Gravity.TOP | Gravity.LEFT; //Orientation
    params.x = 100; //where you want to draw this, coordinates
    params.y = 100;
    //At it to window manager for display, it will be printed over any thing
    windowManager.addView(chatHead, params);


   //Make sure to remove it when you are done, else it will stick there until you reboot
   //Do keep track of same reference of view you added, don't mess with that
   windowManager.removeView(imageView);