如何使用服务在任何其他应用程序上绘制浮动可调整大小的矩形？

Question

我使用可在任何应用程序上看到的服务创建了叠加浮动图标。我已将其实施如下：http://www.piwai.info/chatheads-basics/

现在我想要的是当用户在任何方向上拖动此叠加图标时，应该从叠加图标的初始位置开始绘制矩形到新位置。我尝试使用canvas创建一个可调整大小的矩形并将其添加到windowmanager但是当它被添加到窗口时我无法调整它的大小。

简而言之，这就是我想要实现的目标：

1＆gt;用户按位置说出（x1，y1）

的叠加图标

2＆gt;用户将叠加图标拖动到位置说（x2，y2）

3＆gt;当用户将叠加图标从（x1，y1）拖动到（x2，y2）时，会创建一个矩形。

我已经看过this和this。

这是我到目前为止所尝试的：

    public class MyService extends Service
{
   .....
    public void onCreate()
    {
        super.onCreate();
        floatingFaceBubble = new ImageView(this);
        floatingFaceBubble.setImageResource(R.mipmap.ic_launcher);
        windowManager = (WindowManager) getSystemService(WINDOW_SERVICE);
        final LayoutParams myParams = new WindowManager.LayoutParams(
                LayoutParams.WRAP_CONTENT,
                LayoutParams.WRAP_CONTENT,
                LayoutParams.TYPE_PHONE,
                LayoutParams.FLAG_NOT_FOCUSABLE,
                PixelFormat.TRANSLUCENT);
        myParams.gravity = Gravity.TOP | Gravity.START;
        myParams.x = 0;
        myParams.y = 100;
        windowManager.addView(floatingFaceBubble, myParams);

        try
        {          
            floatingFaceBubble.setOnTouchListener(new View.OnTouchListener()
            {                
                private int initialX;
                private int initialY;
                private float initialTouchX;
                private float initialTouchY;
                private long touchStartTime = 0;

                @Override
                public boolean onTouch(View v, MotionEvent event)
                {                                   
                    switch (event.getAction())
                    {
                        case MotionEvent.ACTION_DOWN:
                            touchStartTime = System.currentTimeMillis();
                            initialX = myParams.x;
                            initialY = myParams.y;
                            initialTouchX = event.getRawX();
                            initialTouchY = event.getRawY();
                            floatingFaceBubble.setVisibility(View.INVISIBLE);

                            rectangleview=new RectangleView(getApplicationContext(),initialTouchX,initialTouchY,event.getRawX(),event.getRawY());                           
                            windowManager.addView(rectangleview,myParams);                                                  

                           break;
                        case MotionEvent.ACTION_UP:   //this case will be executed when button(image) is released                          
                            break;
                        case MotionEvent.ACTION_MOVE:   //this case will be executed when button(image) is moved
                               floatingFaceBubble.setVisibility(View.VISIBLE);
                               myParams.x = initialX + (int) (event.getRawX() - initialTouchX);
                               myParams.y = initialY + (int) (event.getRawY() - initialTouchY);                          
                               windowManager.updateViewLayout(v, myParams);
                               break;}}}}}

这是我的Rectangleview：

public class RectangleView extends View
{
    Paint paint = new Paint();  
    float pointX;
    float pointY;
    float startX;
    float startY;

    public RectangleView(Context context,float x1,float y1,float x2,float y2)
    {
        super(context);
        paint.setStyle(Paint.Style.STROKE);
        paint.setColor(Color.RED);     

        startX=x1;
        startY=y1;
        pointX=x2;
        pointY=y2;    }


    @Override
    public boolean onTouchEvent(MotionEvent event)
    {
        pointX = event.getX();
        pointY = event.getY();
        switch (event.getAction())
        {
            case MotionEvent.ACTION_DOWN:
                startX = pointX;
                startY = pointY;
                return true;
            case MotionEvent.ACTION_MOVE:
                pointX=event.getX();
                pointY=event.getY();
                break;
            default:
                return false;
        }
// Force a view to draw again
        postInvalidate();
        return true;
    }

    @Override
    public void onDraw(Canvas canvas)
    {     
        canvas.drawRect(startX, startY, pointX, pointY,paint);
    }
}