BounceListView.java

package edu.minggo.chat.util;

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 = 1000;
    
    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){ 
		return super.overScrollBy(deltaX, deltaY, scrollX, scrollY, scrollRangeX, scrollRangeY, maxOverScrollX, mMaxYOverscrollDistance, isTouchEvent);  
	}
	
}