Scrollview滑动到最底端加载数据

转载自：http://blog.youkuaiyun.com/leechee_1986/article/details/7191068

要实现一个功能：当Scrollview滑动到最底端的时候需要触发事件加载其他数据。很多人都以为ScrollView可以像ListViev那样setOnScrollListener，其实沒那么简单，因为ScrollView压根就没有该接口，在baidu上兜了一圈没有找到合适的答案，没办法只能google去了，居然一下子解决了这个问题，还是老外比较牛，呵呵，这是我访问的网址： 

http://stackoverflow.com/questions/2864563/how-do-i-know-that-the-scrollview-is-already-scrolled-to-the-bottom

注意，如果数据不满一页的话，会执行onBottom方法！通常要使用懒加载的话数据都会超过一页，所以我沒仔细考虑这个问题！ 

我把ScrollView封装成类了，源码如下： 

package com.dodowaterfall;

import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ScrollView;

public class LazyScrollView extends ScrollView {
	@Override
	protected void onScrollChanged(int l, int t, int oldl, int oldt)
	{
		super.onScrollChanged(l, t, oldl, oldt);
		onScrollListener.onAutoScroll(l, t, oldl, oldt);
	}

	private static final String tag = "LazyScrollView";
	private Handler handler;
	private View view;

	public LazyScrollView(Context context) {
		super(context);

	}

	public LazyScrollView(Context context, AttributeSet attrs) {
		super(context, attrs);

	}

	public LazyScrollView(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);

	}

	// 这个获得总的高度
	public int computeVerticalScrollRange()
	{
		return super.computeHorizontalScrollRange();
	}

	public int computeVerticalScrollOffset()
	{
		return super.computeVerticalScrollOffset();
	}

	private void init()
	{

		this.setOnTouchListener(onTouchListener);
		handler = new Handler() {
			@Override
			public void handleMessage(Message msg)
			{
				// process incoming messages here
				super.handleMessage(msg);
				switch (msg.what)
				{
				case 1:
					if (view.getMeasuredHeight() <= getScrollY() + getHeight())
					{
						if (onScrollListener != null)
						{
							onScrollListener.onBottom();
						}

					} else if (getScrollY() == 0)
					{
						if (onScrollListener != null)
						{
							onScrollListener.onTop();
						}
					} else
					{
						if (onScrollListener != null)
						{
							onScrollListener.onScroll();
						}
					}
					break;
				default:
					break;
				}
			}
		};

	}

	OnTouchListener onTouchListener = new OnTouchListener() {

		@Override
		public boolean onTouch(View v, MotionEvent event)
		{

			switch (event.getAction())
			{
			case MotionEvent.ACTION_DOWN:
				break;
			case MotionEvent.ACTION_UP:
				if (view != null && onScrollListener != null)
				{
					handler.sendMessageDelayed(handler.obtainMessage(1), 200);
				}
				break;

			default:
				break;
			}
			return false;
		}

	};

	/**
	 * 获得参考的View，主要是为了获得它的MeasuredHeight，然后和滚动条的ScrollY+getHeight作比较。
	 */
	public void getView()
	{
		this.view = getChildAt(0);
		if (view != null)
		{
			init();
		}
	}

	/**
	 * 定义接口
	 * 
	 * @author admin
	 * 
	 */
	public interface OnScrollListener {
		void onBottom();

		void onTop();

		void onScroll();

		void onAutoScroll(int l, int t, int oldl, int oldt);
	}

	private OnScrollListener onScrollListener;

	public void setOnScrollListener(OnScrollListener onScrollListener)
	{
		this.onScrollListener = onScrollListener;
	}
}

用的时候也很简单，通常这样使用： 

waterfall_scroll.getView();
		waterfall_scroll.setOnScrollListener(new OnScrollListener() {

			@Override
			public void onTop()
			{
				// 滚动到最顶端
				Log.d("LazyScroll", "Scroll to top");
			}

			@Override
			public void onScroll()
			{

			}

			@Override
			public void onBottom()
			{
				// 滚动到最低端
				AddItemToContainer(++current_page, page_count);
			}