自动反弹的HorizontalScrollView

package com.example.sy;

import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.TranslateAnimation;
import android.widget.HorizontalScrollView;

public class ElasticHScrollView extends HorizontalScrollView {

	private View inner;
	private float x;
	private Rect normal = new Rect();

	public ElasticHScrollView(Context context) {
		super(context);
		// TODO Auto-generated constructor stub
	}

	public ElasticHScrollView(Context context, AttributeSet attrs) {
		super(context, attrs);
		// TODO Auto-generated constructor stub
	}

	@Override
	protected void onFinishInflate() {
		if (getChildCount() > 0) {
			inner = getChildAt(0);
		}
	}

	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		if (inner == null) {
			return super.onTouchEvent(ev);
		} else {
			commOnTouchEvent(ev);
		}
		return super.onTouchEvent(ev);
	}

	public void commOnTouchEvent(MotionEvent ev) {
		int action = ev.getAction();
		switch (action) {
		case MotionEvent.ACTION_DOWN:
			x = ev.getX();
			break;
		case MotionEvent.ACTION_UP:
			if (isNeedAnimation()) {
				animation();
			}
			break;
		case MotionEvent.ACTION_MOVE:
			final float preX = x;
			float nowX = ev.getX();
			int deltaX = (int) (preX - nowX);
			// 滚动
			scrollBy(deltaX, 0);
			x = nowX;
			// 当滚动到最上或最下时就不会再滚动，这是移动布局
			if (isNeedMove()) {
				if (normal.isEmpty()) {
					// 保存正常的布局位置
					normal.set(inner.getLeft(), inner.getTop(),
							inner.getRight(), inner.getBottom());

				}
				// 移动布局
				inner.layout(inner.getLeft() - deltaX, inner.getTop(),
						inner.getRight() - deltaX, inner.getBottom());
			}
			break;
		default:
			break;
		}
	}

	// 开启动画移动

	public void animation() {
		// 开启移动动画
		TranslateAnimation ta = new TranslateAnimation(inner.getLeft(),
				normal.left, 0, 0);
		ta.setDuration(50);
		inner.startAnimation(ta);
		// 设置回到正常的布局位置
		inner.layout(normal.left, normal.top, normal.right, normal.bottom);
		normal.setEmpty();
	}

	// 是否需要开启动画
	public boolean isNeedAnimation() {
		return !normal.isEmpty();
	}

	// 是否需要移动布局
	public boolean isNeedMove() {
		int offset = inner.getMeasuredWidth() - getWidth();
		int scrollX = getScrollX();
		if (scrollX == 0 || scrollX == offset) {
			return true;
		}
		return false;
	}

}