coreSOLO coreSOLO - 6 days ago 5
Android Question

Creating a system overlay window (always on top)

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



I was
following this sample code from the Android source code



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

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" />