自定义拖动圆

//自定义的View

public class MyView extends View {    private static final int WIDTH = 90;    private Rect rect = new Rect(0, 0, WIDTH, WIDTH);// 绘制矩形的区域    private int deltaX, deltaY;// 点击位置和图形边界的偏移量    private int moveX, moveY;    private static Paint paint = new Paint();// 画笔    public MyView(Context context, AttributeSet attrs) {        super(context, attrs);        // TODO Auto-generated constructor stub        paint = new Paint();        paint.setColor(Color.RED);// 填充红色        paint.setAntiAlias(true);    }    @Override    protected void onDraw(Canvas canvas) {        // TODO Auto-generated method stub        //super.onDraw(canvas);        canvas.drawCircle(rect.centerX(), rect.centerY(), WIDTH/2, paint);        //  canvas.drawText("画圆：", 10, 20, p);// 画文本          //canvas.drawCircle(60, 20, 90, p);// 小圆          // p.setAntiAlias(true);// 设置画笔的锯齿效果。 true是去除，大家一看效果就明白了          // canvas.drawCircle(120, 20, 20, p);// 大圆  ////        canvas.drawText("画矩形：", 10, 80, p);//        p.setColor(Color.GRAY);// 设置灰色  //        p.setStyle(Paint.Style.FILL);//设置填满  //        canvas.drawRect(60, 60, 80, 80, p);// 正方形  //        canvas.drawRect(60, 90, 160, 100, p);// 长方形////        canvas.drawText("画三角形：", 10, 200, p);//               // 绘制这个三角形,你可以绘制任意多边形  //         //         Path path = new Path();//         path.moveTo(80, 200);// 此点为多边形的起点  //         path.lineTo(120, 250);//         path.lineTo(80, 250);//         path.close(); // 使这些点构成封闭的多边形  //          canvas.drawPath(path, p);////        //画圆角矩形//        p.setStyle(Paint.Style.FILL);//充满  //        p.setColor(Color.LTGRAY);//        p.setAntiAlias(true);// 设置画笔的锯齿效//        canvas.drawText("画圆角矩形:", 10, 260, p);//        RectF oval3 = new RectF(80, 260, 200, 300);// 设置个新的长方形  //        canvas.drawRoundRect(oval3, 20, 15, p);//第二个参数是x半径，第三个参数是y半径    }    @Override    public boolean onTouchEvent(MotionEvent event) {        int x = (int) event.getX();        int y = (int) event.getY();        switch(event.getAction()) {            case MotionEvent.ACTION_DOWN:                if(!rect.contains(x, y)) {                    return false;//没有在矩形上点击，不处理触摸消息                }                deltaX = x -rect.left;                deltaY = y -rect.top;                break;            case MotionEvent.ACTION_MOVE:            case MotionEvent.ACTION_UP:                Rect old = new Rect(rect);                //更新矩形的位置                rect.left = x - deltaX;                rect.top = y - deltaY;                rect.right = rect.left + WIDTH;                rect.bottom = rect.top + WIDTH;                old.union(rect);//要刷新的区域，求新矩形区域与旧矩形区域的并集                invalidate();//出于效率考虑，设定脏区域，只进行局部刷新，不是刷新整个view                break;        }        return true;//处理了触摸消息，消息不再传递    }}