Android拖动控件

package com.oppo.examples;import android.app.Activity;import android.os.Bundle;import android.util.DisplayMetrics;import android.util.Log;import android.view.MotionEvent;import android.view.View;import android.view.View.OnTouchListener;import android.widget.Button;import android.widget.Toast;public class DraftTest extends Activity {@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);DisplayMetrics dm = getResources().getDisplayMetrics();final int screenWidth = dm.widthPixels;final int screenHeight = dm.heightPixels -50;final Button b=(Button)findViewById(R.id.btn);b.setOnTouchListener(new OnTouchListener(){int lastX, lastY;@Overridepublic boolean onTouch(View v, MotionEvent event) {int ea=event.getAction();switch(ea){case MotionEvent.ACTION_DOWN:lastX = (int) event.getRawX();lastY = (int) event.getRawY();break;case MotionEvent.ACTION_MOVE:int dx =(int)event.getRawX() - lastX;int dy =(int)event.getRawY() - lastY;int left = v.getLeft() + dx;int top = v.getTop() + dy;int right = v.getRight() + dx;int bottom = v.getBottom() + dy;if(left < 0){left = 0;right = left + v.getWidth();}if(right > screenWidth){right = screenWidth;left = right - v.getWidth();}if(top < 0){top = 0;bottom = top + v.getHeight();}if(bottom > screenHeight){bottom = screenHeight;top = bottom - v.getHeight();}v.layout(left, top, right, bottom);lastX = (int) event.getRawX();lastY = (int) event.getRawY();break;case MotionEvent.ACTION_UP:break;        }return false;}});}}