ElasticListView.java

package com.mastercard.android.atmlocator.view;

import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.AbsListView;
import android.widget.GridView;

/**
 * Created by simekadam on 08/02/14.
 */
public class ElasticListView extends GridView implements AbsListView.OnScrollListener, View.OnTouchListener{

	private static int SCROLLING_UP = 1;
	private static int SCROLLING_DOWN = 2;

	private int mScrollState;
	private int mScrollDirection;
	private int mTouchedIndex;

	private View touchedView;

	private int mScrollOffset;
	private int mStartScrollOffset;

	private boolean mAnimate;


	public ElasticListView(Context context) {
		super(context);
		init();
	}

	public ElasticListView(Context context, AttributeSet attrs) {
		super(context, attrs);
		init();
	}

	public ElasticListView(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
		init();
	}

	private void init(){
		mScrollState = SCROLL_STATE_IDLE;
		mScrollDirection = 0;
		mStartScrollOffset = -1;
		mTouchedIndex = Integer.MAX_VALUE;
		mAnimate = true;
		this.setOnTouchListener(this);
		this.setOnScrollListener(this);

	}




	@Override
	public void onScrollStateChanged(AbsListView view, int scrollState) {
		if(mScrollState != scrollState){
			mScrollState = scrollState;

		}
		if(scrollState == SCROLL_STATE_IDLE){
			mStartScrollOffset = Integer.MAX_VALUE;
			mAnimate = true;
		}

	}

	@Override
	public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

		if(mScrollState == SCROLL_STATE_TOUCH_SCROLL && mAnimate){

			if(mStartScrollOffset == Integer.MAX_VALUE){
				touchedView = getChildAt(mTouchedIndex-firstVisibleItem);
				mStartScrollOffset = touchedView.getTop();
				return;
			}
			if(touchedView == null) return;
			Log.d("test", touchedView.getTop()+"px");
			mScrollOffset = touchedView.getTop() - mStartScrollOffset;
			if(mScrollOffset > 0){
					mScrollDirection = SCROLLING_UP;

			}else{
					mScrollDirection = SCROLLING_DOWN;
			}




			if(Math.abs(mScrollOffset) > 200){
				mAnimate = false;
			}
			Log.d("test", "direction:"+ (mScrollDirection == SCROLLING_UP ? "up" :"down")+", scrollOffset:"+mScrollOffset+", toucheId:"+mTouchedIndex + ", fvisible:"+ firstVisibleItem+", " +
				"visibleItemCount:"+visibleItemCount+", " +
				"totalCount:"+totalItemCount);
			int indexOfLastAnimatedItem = mScrollDirection == SCROLLING_DOWN ?
				mTouchedIndex + visibleItemCount :
				mTouchedIndex - visibleItemCount;

			//check for bounds
			if(indexOfLastAnimatedItem >= getChildCount()) {
				indexOfLastAnimatedItem = getChildCount()-1;
			}
			else if(indexOfLastAnimatedItem < 0){
				indexOfLastAnimatedItem = 0;
			}

			if(mScrollDirection == SCROLLING_DOWN){
				setAnimationForScrollingDown(mTouchedIndex, indexOfLastAnimatedItem, firstVisibleItem);
			}else{
				setAnimationForScrollingUp(mTouchedIndex, indexOfLastAnimatedItem, firstVisibleItem);
			}

		}
	}

	private void setAnimationForScrollingUp(int indexOfTouchedChild, int indexOflastAnimatedChild, int firstVisibleIndex) {
		for(int i = indexOfTouchedChild+1; i <= indexOflastAnimatedChild; i++){
			View v = getChildAt(i-firstVisibleIndex);
			v.setTranslationY((-1*mScrollOffset)-v.getTranslationY());
			v.animate().translationY(0).setDuration(300).setStartDelay(50*i).start();
		}
	}

	private void setAnimationForScrollingDown(int indexOfTouchedChild, int indexOflastAnimatedChild,  int firstVisibleIndex) {
		for(int i = indexOflastAnimatedChild; i > indexOfTouchedChild; i--){
			View v = getChildAt(i - firstVisibleIndex);
			v.setTranslationY((-1*mScrollOffset) - v.getTranslationY());
			v.animate().translationY(0).setDuration(300).setStartDelay(50*(i-indexOfTouchedChild)).start();
		}
	}


	@Override
	public boolean onTouch(View v, MotionEvent event) {
		switch (event.getActionMasked()) {
			case MotionEvent.ACTION_DOWN: 		
				Rect rect = new Rect();
				int childCount = getChildCount();
				int[] listViewCoords = new int[2];
				getLocationOnScreen(listViewCoords);
				int x = (int) event.getRawX() - listViewCoords[0];
				int y = (int) event.getRawY() - listViewCoords[1];
				View child;
				for (int i = 0; i < childCount; i++) {
					child = getChildAt(i);
					child.getHitRect(rect);
					if (rect.contains(x, y)) {
						mTouchedIndex = getPositionForView(child); // This is your down view
						break;
					}
				}
				return false;

		}
		return false;

	}

}