BounceListView.java

/*
 * Copyright (C) 2013 HalZhang.
 *
 * http://www.gnu.org/licenses/gpl-3.0.txt
 */

package com.halzhang.android.examples.bouncelistviewexample;

import android.annotation.TargetApi;
import android.content.Context;
import android.os.Build;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.widget.ListView;

/**
 * BounceListViewExample
 * <p>
 * </p>
 * 
 * @author <a href="http://weibo.com/halzhang">Hal</a>
 * @version Aug 26, 2013
 */
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);
    }

    @TargetApi(Build.VERSION_CODES.GINGERBREAD)
    @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);
    }

}