android - Creating a system overlay window (always on top)

Question

I'm trying to create an always-op-top button/clickable-image which stays on top of all the windows all the time.

The proof of concept is

• here - Smart Taskbar (on AppBrain)
• and here V1.4.0 Sidebar style SWKey - Button savior (on xda-developers)

I have been successful and have a running service now. The service displays some text on top left corner of screen all the time while user can freely interact with rest of apps in normal manner.

What I'm doing is subclass ViewGroup and add it to root window manager with flag TYPE_SYSTEM_OVERLAY. Now I want to add a button/clickable-image in place of this text which can receive touch events on itself. I tried overriding "onTouchEvent" for the whole ViewGroup but it does not receive any event.

How can I receive events only on certain parts of my always-on-top view group? Kindly suggest.

public class HUD extends Service {
    HUDView mView;

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

    @Override
    public void onCreate() {
        super.onCreate();
        Toast.makeText(getBaseContext(),"onCreate", Toast.LENGTH_LONG).show();
        mView = new HUDView(this);
        WindowManager.LayoutParams params = new WindowManager.LayoutParams(
                WindowManager.LayoutParams.WRAP_CONTENT,
                WindowManager.LayoutParams.WRAP_CONTENT,
                WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY,
                0,
//              WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
//                      | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE,
                PixelFormat.TRANSLUCENT);
        params.gravity = Gravity.RIGHT | Gravity.TOP;
        params.setTitle("Load Average");
        WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
        wm.addView(mView, params);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Toast.makeText(getBaseContext(),"onDestroy", Toast.LENGTH_LONG).show();
        if(mView != null)
        {
            ((WindowManager) getSystemService(WINDOW_SERVICE)).removeView(mView);
            mView = null;
        }
    }
}

class HUDView extends ViewGroup {
    private Paint mLoadPaint;

    public HUDView(Context context) {
        super(context);
        Toast.makeText(getContext(),"HUDView", Toast.LENGTH_LONG).show();

        mLoadPaint = new Paint();
        mLoadPaint.setAntiAlias(true);
        mLoadPaint.setTextSize(10);
        mLoadPaint.setARGB(255, 255, 0, 0);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawText("Hello World", 5, 15, mLoadPaint);
    }

    @Override
    protected void onLayout(boolean arg0, int arg1, int arg2, int arg3, int arg4) {
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        //return super.onTouchEvent(event);
        Toast.makeText(getContext(),"onTouchEvent", Toast.LENGTH_LONG).show();
        return true;
    }
}

Answer 1

This might be a stupid solution. But it works. If you can improve it, please let me know.

OnCreate of your Service: I have used WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH flag. This is the only change in service.

@Override
    public void onCreate() {
        super.onCreate();
        Toast.makeText(getBaseContext(),"onCreate", Toast.LENGTH_LONG).show();
        mView = new HUDView(this);
        WindowManager.LayoutParams params = new WindowManager.LayoutParams(
                WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY,
                WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH,
                PixelFormat.TRANSLUCENT);
        params.gravity = Gravity.RIGHT | Gravity.TOP;
        params.setTitle("Load Average");
        WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
        wm.addView(mView, params);
    }

Now, you will start getting each and every click event. So, you need to rectify in your event handler.

In your ViewGroup touch event

@Override
public boolean onTouchEvent(MotionEvent event) {

    // ATTENTION: GET THE X,Y OF EVENT FROM THE PARAMETER
    // THEN CHECK IF THAT IS INSIDE YOUR DESIRED AREA


    Toast.makeText(getContext(),"onTouchEvent", Toast.LENGTH_LONG).show();
    return true;
}

Also you may need to add this permission to your manifest:

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