android拖动图片移动效果

java代码
Java代码 
package com.twy.test; 
 
import android.app.Activity; 
import android.os.Bundle; 
import android.util.DisplayMetrics; 
import android.view.MotionEvent; 
import android.view.View; 
import android.view.View.OnTouchListener; 
import android.widget.ImageView; 
 
public class TestDemo extends Activity { 
    private ImageView img1; 
    private ImageView img2; 
    private int screenWidth; 
    private int screenHeight; 
 
    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.main); 
 
        img1 = (ImageView) findViewById(R.id.imageView1); 
        img2 = (ImageView) findViewById(R.id.imageView2); 
 
        DisplayMetrics dm = getResources().getDisplayMetrics(); 
        screenWidth = dm.widthPixels; 
        screenHeight = dm.heightPixels - 50; 
 
        img1.setOnTouchListener(movingEventListener); 
        img2.setOnTouchListener(movingEventListener); 
 
    } 
 
    private OnTouchListener movingEventListener = new OnTouchListener() { 
        int lastX, lastY; 
 
        @Override 
        public boolean onTouch(View v, MotionEvent event) { 
            switch (event.getAction()) { 
            case MotionEvent.ACTION_DOWN: 
                lastX = (int) event.getRawX(); 
                lastY = (int) event.getRawY(); 
                break; 
            case MotionEvent.ACTION_MOVE: 
                int dx = (int) event.getRawX() - lastX;