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colorballs 是一个有两个位图的类（此处未显示），我正在努力寻找是否将位图拖放到屏幕上的“正方形”（请参阅​​下面的“绘制方法”）中。然后位图不应该再被拖动，如果相同的位图移动到其他任何地方但不在正方形内，当我停止移动位图时它应该恢复到原始位置。请帮助代码。

     // the method that draws the balls
       @Override protected void onDraw(Canvas canvas) {
        //canvas.drawColor(0xFFCCCCCC);     //if you want another background color       

    //draw the balls on the canvas
    for (ColorBall ball : colorballs) {
        canvas.drawBitmap(ball.getBitmap(), ball.getX(), ball.getY(), null);


      }

    // draw the square.
    Paint rectPaint = new Paint();
    // color of the border
    rectPaint.setColor(Color.BLUE);
    rectPaint.setStrokeWidth(1);        
    rectPaint.setStyle(Paint.Style.STROKE);

    int w = this.getWidth(), h = this.getHeight();
    int offset = (h - w)/2;
    int step =w/3;
     rect= new Rect (0, offset+0*step, step, offset+step*1);
    canvas.drawRect(rect, rectPaint);

}

       // events when touching the screen
      public boolean onTouchEvent(MotionEvent event) {
    int eventaction = event.getAction(); 

    int X = (int)event.getX(); 
    int Y = (int)event.getY(); 
    ballTouchedFlag =false;

    switch (eventaction ) { 

    case MotionEvent.ACTION_DOWN: // touch down so check if the finger is on a ball
        balID = 0;
        for (ColorBall ball : colorballs) {
            // check if inside the bounds of the ball (circle)
            // get the center for the ball
            int centerX = ball.getX() + 25;
            int centerY = ball.getY() + 25;

            // calculate the radius from the touch to the center of the ball
            double radCircle  = Math.sqrt( (double) (((centerX-X)*(centerX-X)) + (centerY-Y)*(centerY-Y)));

            // if the radius is smaller then 23 (radius of a ball is 22), then it must be on the ball
            if (radCircle < 23){
                balID = ball.getID();
                initPoint.x=X;
                initPoint.y=Y;
                ballTouchedFlag =true;
                break;
            }


          }

         break; 


    case MotionEvent.ACTION_MOVE:   // touch drag with the ball
        // move the balls the same as the finger
        if (balID > 0 ) {
            colorballs[balID-1].setX(X-25);
            colorballs[balID-1].setY(Y-25);
        }

        break; 

    case MotionEvent.ACTION_UP: 
        // touch drop - just do things here after dropping
        // Determine if the ball is touched.


         break; 
    }  

    // redraw the canvas
    invalidate(); 
    return true;
}
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1 回答 1

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我想出了我想要实现的目标，这是我在上面代码中的更新，

在 MotionEvent.ACTION_DOWN 中，我做了以下更改

  // if the click image is not inside the rectangle

    if (radCircle < 23 && rect.contains(colorballs[balID-1].getX(), colorballs[balID-1].getY() == false){
            balID = ball.getID();
            initPoint.x=X;
            initPoint.y=Y;
            ballTouchedFlag =true;
            break;
        }

在 MotionEvent.Move 中，添加以下行

   if ( balID > 0 && rect.contains(colorballs[balID-1].getX(), colorballs[balID-1].getY() == false )
   {.....}

在 MotionEvent.ACTION_UP 中，我添加了以下代码

     // Now, when you drop the clicked bitmap, if it is not not in the square, store it            //  first position
   if ( rect.contains(colorballs[balID-1].getX(), colorballs[balID-1].getY() == false )
 colorballs[balID-1].setX(initPoint.x-25);
        colorballs[balID-1].setY(initPoint.y-25);
于 2013-03-02T00:20:52.923 回答