Creating a system overlay window (always on top)

Question

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" />

Following @Sam Lu's answer, Indeed Android 4.x blocks certain types from listening to outside touch events, but some types, such as TYPE_SYSTEM_ALERT, still do the job.

Example

    WindowManager.LayoutParams params = new WindowManager.LayoutParams(
            WindowManager.LayoutParams.MATCH_PARENT,
            WindowManager.LayoutParams.MATCH_PARENT,
            WindowManager.LayoutParams.TYPE_SYSTEM_ALERT,
            WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
                    | WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL
                    | WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH,
            PixelFormat.TRANSLUCENT);

    WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
    LayoutInflater inflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
    View myView = inflater.inflate(R.layout.my_view, null);
    myView.setOnTouchListener(new OnTouchListener() {
       @Override
       public boolean onTouch(View v, MotionEvent event) {
           Log.d(TAG, "touch me");
           return true;
       }
     });

    // Add layout to window manager
    wm.addView(myView, params);

Permissions

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

Starting with Android 4.x, Android team fixed a potential security problem by adding a new function adjustWindowParamsLw() in which it will add FLAG_NOT_FOCUSABLE, FLAG_NOT_TOUCHABLE and remove FLAG_WATCH_OUTSIDE_TOUCH flags for TYPE_SYSTEM_OVERLAY windows.

That is, a TYPE_SYSTEM_OVERLAY window won't receive any touch event on ICS platform and, of course, to use TYPE_SYSTEM_OVERLAY is not a workable solution for ICS and future devices.

I'm one of the developers of the Tooleap SDK. We also provide a way for developers to display always on top windows and buttons, and and we have dealt with a similar situation.

One problem the answers here haven't addressed is that of the Android "Secured Buttons".

Secured buttons have the filterTouchesWhenObscured property which means they can't be interacted with, if placed under a window, even if that window does not receive any touches. Quoting the Android documentation:

Specifies whether to filter touches when the view's window is obscured by another visible window. When set to true, the view will not receive touches whenever a toast, dialog or other window appears above the view's window. Refer to the {@link android.view.View} security documentation for more details.

An example of such a button is the install button when you try to install third party apks. Any app can display such a button if adding to the view layout the following line:

android:filterTouchesWhenObscured="true"

If you display an always-on-top window over a "Secured Button", so all the secured button parts that are covered by an overlay will not handle any touches, even if that overlay is not clickable. So if you are planing to display such a window, you should provide a way for the user to move it or dismiss it. And if a part of your overlay is transparent, take into account that your user might be confused why is a certain button in the underlying app is not working for him suddenly.

WORKING ALWAYS ON TOP IMAGE BUTTON

first of all sorry for my english

i edit your codes and make working image button that listens his touch event do not give touch control to his background elements.

also it gives touch listeners to out of other elements

button alingments are bottom and left

you can chage alingments but you need to chages cordinats in touch event in the if element

import android.annotation.SuppressLint;

import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.PixelFormat;
import android.os.IBinder;
import android.util.Log;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.Toast;

public class HepUstte extends Service {
    HUDView mView;

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

        Toast.makeText(getBaseContext(),"onCreate", Toast.LENGTH_LONG).show();

        final Bitmap kangoo = BitmapFactory.decodeResource(getResources(),
                R.drawable.logo_l);


        WindowManager.LayoutParams params = new WindowManager.LayoutParams(
                kangoo.getWidth(), 
                kangoo.getHeight(),
                WindowManager.LayoutParams.TYPE_SYSTEM_ALERT,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
                |WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL
                |WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH,
                 PixelFormat.TRANSLUCENT);






        params.gravity = Gravity.LEFT | Gravity.BOTTOM;
        params.setTitle("Load Average");
        WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);



        mView = new HUDView(this,kangoo);

        mView.setOnTouchListener(new OnTouchListener() {


            @Override
            public boolean onTouch(View arg0, MotionEvent arg1) {
                // TODO Auto-generated method stub
                //Log.e("kordinatlar", arg1.getX()+":"+arg1.getY()+":"+display.getHeight()+":"+kangoo.getHeight());
                if(arg1.getX()<kangoo.getWidth() & arg1.getY()>0)
                {
                 Log.d("tıklandı", "touch me");
                }
                return false;
            }
             });


        wm.addView(mView, params);



        }



    @Override
    public IBinder onBind(Intent arg0) {
        // TODO Auto-generated method stub
        return null;
    }

}



@SuppressLint("DrawAllocation")
class HUDView extends ViewGroup {


    Bitmap kangoo;

    public HUDView(Context context,Bitmap kangoo) {
        super(context);

        this.kangoo=kangoo;



    }


    protected void onDraw(Canvas canvas) {
        //super.onDraw(canvas);


        // delete below line if you want transparent back color, but to understand the sizes use back color
        canvas.drawColor(Color.BLACK);

        canvas.drawBitmap(kangoo,0 , 0, null); 


        //canvas.drawText("Hello World", 5, 15, mLoadPaint);

    }


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

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

        return true;
    }
}

TYPE_SYSTEM_OVERLAY This constant was deprecated in since API level 26. Use TYPE_APPLICATION_OVERLAY instead. or **for users below and above android 8

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    LAYOUT_FLAG = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
} else {
    LAYOUT_FLAG = WindowManager.LayoutParams.TYPE_PHONE;
}

Try this. Works fine in ICS. If You want to stop service simply click the notification generated in statusbar.

 public class HUD extends Service
 {
    protected boolean foreground = false;
    protected boolean cancelNotification = false;
    private Notification notification;
    private View myView;
    protected int id = 0;
    private WindowManager wm;
    private WindowManager.LayoutParams params;
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
    @Override
    public void onCreate() {
        super.onCreate();
       // System.exit(0);
        Toast.makeText(getBaseContext(),"onCreate", Toast.LENGTH_SHORT).show();
        params = new WindowManager.LayoutParams(WindowManager.LayoutParams.WRAP_CONTENT, WindowManager.LayoutParams.WRAP_CONTENT,
                WindowManager.LayoutParams.TYPE_PHONE, WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL
                        | WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE, PixelFormat.TRANSLUCENT);
        params.gravity=Gravity.TOP|Gravity.LEFT;
    wm = (WindowManager) getSystemService(WINDOW_SERVICE);
    inflateview();
    foregroundNotification(1);
    //moveToForeground(1,n,true);
    }     
   @Override
    public void onDestroy() {
        super.onDestroy();
        ((NotificationManager) getSystemService(NOTIFICATION_SERVICE)).cancel(0);
        Toast.makeText(getBaseContext(),"onDestroy", Toast.LENGTH_SHORT).show();
        if(myView != null)
        {
            ((WindowManager) getSystemService(WINDOW_SERVICE)).removeView(myView);
            myView = null;
        }
    }
    protected Notification foregroundNotification(int notificationId) 
   {    
    notification = new Notification(R.drawable.ic_launcher, "my Notification", System.currentTimeMillis());    
        notification.flags = notification.flags | Notification.FLAG_ONGOING_EVENT | Notification.FLAG_ONLY_ALERT_ONCE;   
        notification.setLatestEventInfo(this, "my Notification", "my Notification", notificationIntent());          
        ((NotificationManager) getSystemService(NOTIFICATION_SERVICE)).notify(id, notification);            
        return notification;
    }
    private PendingIntent notificationIntent() {
        Intent intent = new Intent(this, stopservice.class);    
        PendingIntent pending = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);    
        return pending;
    }
    public void inflateview()
    {
         LayoutInflater inflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
            myView = inflater.inflate(R.layout.activity_button, null);
            myView.setOnTouchListener(new OnTouchListener() {
               @Override
               public boolean onTouch(View v, MotionEvent event) {
                   Toast.makeText(getBaseContext(),"onToasttt", Toast.LENGTH_SHORT).show();
                   return false;
               }
             });
            // Add layout to window manager
            wm.addView(myView, params); 
    }
}

UPDATE

Sample here

To create an overlay view, when setting up the LayoutParams DON'T set the type to TYPE_SYSTEM_OVERLAY.

Instead set it to TYPE_PHONE.

Use the following flags:

FLAG_NOT_TOUCH_MODAL

FLAG_WATCH_OUTSIDE_TOUCH