Android floating window

calling-service

            button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    if(Build.VERSION.SDK_INT>=23){
                        if(Settings.canDrawOverlays(context)){
                            context.startService(new Intent(MainActivity.THIS, PerfmonService.class));
                        }
                        else {
                            Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION);
                            intent.setData(Uri.parse("package:" + context.getPackageName()));
                            context.startActivity(intent);
                        }
                    }
                    else{
                        context.startService(new Intent(MainActivity.THIS, PerfmonService.class));
                    }
                }
            });

floating-window-in-service

 void init(){
        params=new WindowManager.LayoutParams();
        windowManager=(WindowManager)getApplication().getSystemService(Context.WINDOW_SERVICE);
        if(Build.VERSION.SDK_INT>=26){
            params.type = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
        }
        else{
            params.type = WindowManager.LayoutParams.TYPE_SYSTEM_ALERT;
        }

        params.format = PixelFormat.RGBA_8888;
        params.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;
        params.gravity = Gravity.LEFT | Gravity.TOP;
        params.x = 0;
        params.y = 0;
        params.width = 500;
        params.height = 300;
        main= (LinearLayout)LayoutInflater.from(this).inflate(R.layout.float_perfmon,null);
        textView=main.findViewById(R.id.perfmon1);
        linearLayout1=main.findViewById(R.id.perfmonl1);
        textView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                stopSelf();
                if(LBuild.DEBUG)
                    Log.d(TAG,"Tried to stop");
            }
        });


        windowManager.addView(main,params);

        main.measure(View.MeasureSpec.UNSPECIFIED,View.MeasureSpec.UNSPECIFIED);

        int resourceId = getResources().getIdentifier("status_bar_height","dimen","android");
        if (resourceId > 0) {
            statusBarHeight = getResources().getDimensionPixelSize(resourceId);
        }

        main.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                params.x = (int) event.getRawX()-main.getWidth()/2;
                params.y = (int) event.getRawY() - statusBarHeight-main.getHeight()/2;
                windowManager.updateViewLayout(main,params);

                return false;
            }
        });
        new refreshInfo().start();
    }