自定义可移动view

import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Rect;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;public class CustomView extends View {private static final int WIDTH = 40;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 static Paint paint = new Paint();//画笔public CustomView(Context context, AttributeSet attrs) {super(context, attrs);paint = new Paint();paint.setColor(Color.RED);//填充红色}@Overrideprotected void onDraw(Canvas canvas) {canvas.drawRect(rect, paint);//画矩形}@Overridepublic 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(old);//出于效率考虑，设定脏区域，只进行局部刷新，不是刷新整个viewbreak;}return true;//处理了触摸消息，消息不再传递}}