android仿照ipone的弹性效果

package com.example.bounce;

import android.content.Context;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.widget.ListView;
 
public class BounceListView extends ListView{
    private static final int MAX_Y_OVERSCROLL_DISTANCE = 200;
     
    private Context mContext;
    private int mMaxYOverscrollDistance;
     
    public BounceListView(Context context){
        super(context);
        mContext = context;
        initBounceListView();
    }
     
    public BounceListView(Context context, AttributeSet attrs){
        super(context, attrs);
        mContext = context;
        initBounceListView();
    }
     
    public BounceListView(Context context, AttributeSet attrs, int defStyle){
        super(context, attrs, defStyle);
        mContext = context;
        initBounceListView();
    }
     
    private void initBounceListView(){
        //get the density of the screen and do some maths with it on the max overscroll distance
        //variable so that you get similar behaviors no matter what the screen size
         
        final DisplayMetrics metrics = mContext.getResources().getDisplayMetrics();
            final float density = metrics.density;
         
        mMaxYOverscrollDistance = (int) (density * MAX_Y_OVERSCROLL_DISTANCE);
    }
     
    @Override
    protected boolean overScrollBy(int deltaX, int deltaY, int scrollX, int scrollY, int scrollRangeX, int scrollRangeY, int maxOverScrollX, int maxOverScrollY, boolean isTouchEvent){ 
        //This is where the magic happens, we have replaced the incoming maxOverScrollY with our own custom variable mMaxYOverscrollDistance; 
        return super.overScrollBy(deltaX, deltaY, scrollX, scrollY, scrollRangeX, scrollRangeY, maxOverScrollX, mMaxYOverscrollDistance, isTouchEvent);  
    }
     
}

　　

package com.example.bounce;
import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
 
public class BounceListViewActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_bounce_list_view);
        BounceListView mBounceLv = (BounceListView)findViewById(R.id.list);
        mBounceLv.setAdapter(new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,getData()));
    }
    private List<String> getData(){
         
        List<String> data = new ArrayList<String>();
        data.add("测试数据1");
        data.add("测试数据2");
        data.add("测试数据3");
        data.add("测试数据4");
        data.add("测试数据5");
        data.add("测试数据6");
        data.add("测试数据7");
        data.add("测试数据8");
        data.add("测试数据9");
        data.add("测试数据10");
        data.add("测试数据11");
        data.add("测试数据12");
        data.add("测试数据13");
        return data;
    }
}