Android下拉刷新上拉载入控件，对全部View通用！

    转载请声明出处http://blog.csdn.net/zhongkejingwang/article/details/38868463

     前面写过一篇关于下拉刷新控件的博客下拉刷新控件终结者：PullToRefreshLayout，后来看到好多人还有上拉载入很多其它的需求，于是就在前面下拉刷新控件的基础上进行了改进，加了上拉载入的功能。不仅如此，我已经把它改成了对全部View都通用！能够随心所欲使用这两个功能~~

    我做了一个大集合的demo，实现了ListView、GridView、ExpandableListView、ScrollView、WebView、ImageView、TextView的下拉刷新和上拉载入。后面会提供demo的下载地址。（csdn上的demo有小bug，最新代码已上传到github：https://github.com/jingchenUSTC/PullToRefreshAndLoad)

    按照惯例，以下将会是一大波效果图：

demo首页也是可下拉的ListView，在底下能够增加table：

                                            

ListView：

                

GridView：

                

ExpandableListView：

                

ScrollView：

               

WebView：

               

ImageView：

                

TextView：

                

    非常不错吧？最后的ImageView和TextView是最简单的，直接在以下的接口方法里返回true。

    添加上拉载入非常easy，和管理下拉头一样，再多管理一个上拉头，也不费事；至于把它改成通用的就须要统一一下View的行为了，为此，我定义了这样一个接口：

package com.jingchen.pulltorefresh.pullableview;

public interface Pullable
{
	/**
	 * 推断能否够下拉，假设不须要下拉功能能够直接return false
	 * 
	 * @return true假设能够下拉否则返回false
	 */
	boolean canPullDown();

	/**
	 * 推断能否够上拉，假设不须要上拉功能能够直接return false
	 * 
	 * @return true假设能够上拉否则返回false
	 */
	boolean canPullUp();
}

从接口名就能够看出它是一个提供推断是否可拉的方法的接口。这个接口的两个方法，canPullDown()是推断何时能够下拉的方法，canPullUp()则是推断何时能够上拉，我在demo中的推断是滑到顶部的时候能够下拉，滑究竟部的时候能够上拉。全部须要上拉和下拉的View都须要实现这个接口。后面会给出一些View的实现。先来看看改进后的自己定义的布局PullToRefreshLayout，添加了一个上拉头，下拉头和上拉头之间的View是实现了Pullable接口的pullableView。相比前面的版本号，这里有修改的须要注意的地方例如以下：

1、添加了上拉头，对应的也添加了控制变量。

2、拉动时消除content_view事件防止误触发不再使用反射，直接设置                       event.setAction(MotionEvent.ACTION_CANCEL)。

3、消除了拉动过程中的多点触碰导致的剧变。

4、不再设置content_view的onTouListener，让使用者能够更加自由的设置监听器。

   这个PullToRefreshLayout仅仅负责管理三个控件，假设一个View须要有上拉下拉功能则仅仅需实现接口即可了。以下看PullToRefreshLayout的代码，凝视写了好多：

package com.jingchen.pulltorefresh;

import java.util.Timer;
import java.util.TimerTask;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.LinearGradient;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.RectF;
import android.graphics.Shader.TileMode;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.AnimationUtils;
import android.view.animation.LinearInterpolator;
import android.view.animation.RotateAnimation;
import android.widget.RelativeLayout;
import android.widget.TextView;

import com.jingchen.pulltorefresh.pullableview.Pullable;

/**
 * 自己定义的布局，用来管理三个子控件，当中一个是下拉头，一个是包括内容的pullableView（能够是实现Pullable接口的的不论什么View），
 * 另一个上拉头
 * 
 * @author 陈靖
 */
public class PullToRefreshLayout extends RelativeLayout
{
	public static final String TAG = "PullToRefreshLayout";
	// 初始状态
	public static final int INIT = 0;
	// 释放刷新
	public static final int RELEASE_TO_REFRESH = 1;
	// 正在刷新
	public static final int REFRESHING = 2;
	// 释放载入
	public static final int RELEASE_TO_LOAD = 3;
	// 正在载入
	public static final int LOADING = 4;
	// 操作完毕
	public static final int DONE = 5;
	// 当前状态
	private int state = INIT;
	// 刷新回调接口
	private OnRefreshListener mListener;
	// 刷新成功
	public static final int SUCCEED = 0;
	// 刷新失败
	public static final int FAIL = 1;
	// 按下Y坐标，上一个事件点Y坐标
	private float downY, lastY;

	// 下拉的距离。注意：pullDownY和pullUpY不可能同一时候不为0
	public float pullDownY = 0;
	// 上拉的距离
	private float pullUpY = 0;

	// 释放刷新的距离
	private float refreshDist = 200;
	// 释放载入的距离
	private float loadmoreDist = 200;

	private MyTimer timer;
	// 回滚速度
	public float MOVE_SPEED = 8;
	// 第一次运行布局
	private boolean isLayout = false;
	// 在刷新过程中滑动操作
	private boolean isTouch = false;
	// 手指滑动距离与下拉头的滑动距离比，中间会随正切函数变化
	private float radio = 2;

	// 下拉箭头的转180°动画
	private RotateAnimation rotateAnimation;
	// 均匀旋转动画
	private RotateAnimation refreshingAnimation;

	// 下拉头
	private View refreshView;
	// 下拉的箭头
	private View pullView;
	// 正在刷新的图标
	private View refreshingView;
	// 刷新结果图标
	private View refreshStateImageView;
	// 刷新结果：成功或失败
	private TextView refreshStateTextView;

	// 上拉头
	private View loadmoreView;
	// 上拉的箭头
	private View pullUpView;
	// 正在载入的图标
	private View loadingView;
	// 载入结果图标
	private View loadStateImageView;
	// 载入结果：成功或失败
	private TextView loadStateTextView;

	// 实现了Pullable接口的View
	private View pullableView;
	// 过滤多点触碰
	private int mEvents;
	// 这两个变量用来控制pull的方向，假设不加控制，当情况满足可上拉又可下拉时没法下拉
	private boolean canPullDown = true;
	private boolean canPullUp = true;

	/**
	 * 运行自己主动回滚的handler
	 */
	Handler updateHandler = new Handler()
	{

		@Override
		public void handleMessage(Message msg)
		{
			// 回弹速度随下拉距离moveDeltaY增大而增大
			MOVE_SPEED = (float) (8 + 5 * Math.tan(Math.PI / 2
					/ getMeasuredHeight() * (pullDownY + Math.abs(pullUpY))));
			if (!isTouch)
			{
				// 正在刷新，且没有往上推的话则悬停，显示"正在刷新..."
				if (state == REFRESHING && pullDownY <= refreshDist)
				{
					pullDownY = refreshDist;
					timer.cancel();
				} else if (state == LOADING && -pullUpY <= loadmoreDist)
				{
					pullUpY = -loadmoreDist;
					timer.cancel();
				}

			}
			if (pullDownY > 0)
				pullDownY -= MOVE_SPEED;
			else if (pullUpY < 0)
				pullUpY += MOVE_SPEED;
			if (pullDownY < 0)
			{
				// 已完毕回弹
				pullDownY = 0;
				pullView.clearAnimation();
				// 隐藏下拉头时有可能还在刷新，仅仅有当前状态不是正在刷新时才改变状态
				if (state != REFRESHING && state != LOADING)
					changeState(INIT);
				timer.cancel();
			}
			if (pullUpY > 0)
			{
				// 已完毕回弹
				pullUpY = 0;
				pullUpView.clearAnimation();
				// 隐藏下拉头时有可能还在刷新，仅仅有当前状态不是正在刷新时才改变状态
				if (state != REFRESHING && state != LOADING)
					changeState(INIT);
				timer.cancel();
			}
			// 刷新布局,会自己主动调用onLayout
			requestLayout();
		}

	};

	public void setOnRefreshListener(OnRefreshListener listener)
	{
		mListener = listener;
	}

	public PullToRefreshLayout(Context context)
	{
		super(context);
		initView(context);
	}

	public PullToRefreshLayout(Context context, AttributeSet attrs)
	{
		super(context, attrs);
		initView(context);
	}

	public PullToRefreshLayout(Context context, AttributeSet attrs, int defStyle)
	{
		super(context, attrs, defStyle);
		initView(context);
	}

	private void initView(Context context)
	{
		timer = new MyTimer(updateHandler);
		rotateAnimation = (RotateAnimation) AnimationUtils.loadAnimation(
				context, R.anim.reverse_anim);
		refreshingAnimation = (RotateAnimation) AnimationUtils.loadAnimation(
				context, R.anim.rotating);
		// 加入匀速转动动画
		LinearInterpolator lir = new LinearInterpolator();
		rotateAnimation.setInterpolator(lir);
		refreshingAnimation.setInterpolator(lir);
	}

	private void hide()
	{
		timer.schedule(5);
	}

	/**
	 * 完毕刷新操作，显示刷新结果。注意：刷新完毕后一定要调用这种方法
	 */
	/**
	 * @param refreshResult
	 *            PullToRefreshLayout.SUCCEED代表成功，PullToRefreshLayout.FAIL代表失败
	 */
	public void refreshFinish(int refreshResult)
	{
		refreshingView.clearAnimation();
		refreshingView.setVisibility(View.GONE);
		switch (refreshResult)
		{
		case SUCCEED:
			// 刷新成功
			refreshStateImageView.setVisibility(View.VISIBLE);
			refreshStateTextView.setText(R.string.refresh_succeed);
			refreshStateImageView
					.setBackgroundResource(R.drawable.refresh_succeed);
			break;
		case FAIL:
		default:
			// 刷新失败
			refreshStateImageView.setVisibility(View.VISIBLE);
			refreshStateTextView.setText(R.string.refresh_fail);
			refreshStateImageView
					.setBackgroundResource(R.drawable.refresh_failed);
			break;
		}
		// 刷新结果停留1秒
		new Handler()
		{
			@Override
			public void handleMessage(Message msg)
			{
				changeState(DONE);
				hide();
			}
		}.sendEmptyMessageDelayed(0, 1000);
	}

	/**
	 * 载入完毕，显示载入结果。注意：载入完毕后一定要调用这种方法
	 * 
	 * @param refreshResult
	 *            PullToRefreshLayout.SUCCEED代表成功，PullToRefreshLayout.FAIL代表失败
	 */
	public void loadmoreFinish(int refreshResult)
	{
		loadingView.clearAnimation();
		loadingView.setVisibility(View.GONE);
		switch (refreshResult)
		{
		case SUCCEED:
			// 载入成功
			loadStateImageView.setVisibility(View.VISIBLE);
			loadStateTextView.setText(R.string.load_succeed);
			loadStateImageView.setBackgroundResource(R.drawable.load_succeed);
			break;
		case FAIL:
		default:
			// 载入失败
			loadStateImageView.setVisibility(View.VISIBLE);
			loadStateTextView.setText(R.string.load_fail);
			loadStateImageView.setBackgroundResource(R.drawable.load_failed);
			break;
		}
		// 刷新结果停留1秒
		new Handler()
		{
			@Override
			public void handleMessage(Message msg)
			{
				changeState(DONE);
				hide();
			}
		}.sendEmptyMessageDelayed(0, 1000);
	}

	private void changeState(int to)
	{
		state = to;
		switch (state)
		{
		case INIT:
			// 下拉布局初始状态
			refreshStateImageView.setVisibility(View.GONE);
			refreshStateTextView.setText(R.string.pull_to_refresh);
			pullView.clearAnimation();
			pullView.setVisibility(View.VISIBLE);
			// 上拉布局初始状态
			loadStateImageView.setVisibility(View.GONE);
			loadStateTextView.setText(R.string.pullup_to_load);
			pullUpView.clearAnimation();
			pullUpView.setVisibility(View.VISIBLE);
			break;
		case RELEASE_TO_REFRESH:
			// 释放刷新状态
			refreshStateTextView.setText(R.string.release_to_refresh);
			pullView.startAnimation(rotateAnimation);
			break;
		case REFRESHING:
			// 正在刷新状态
			pullView.clearAnimation();
			refreshingView.setVisibility(View.VISIBLE);
			pullView.setVisibility(View.INVISIBLE);
			refreshingView.startAnimation(refreshingAnimation);
			refreshStateTextView.setText(R.string.refreshing);
			break;
		case RELEASE_TO_LOAD:
			// 释放载入状态
			loadStateTextView.setText(R.string.release_to_load);
			pullUpView.startAnimation(rotateAnimation);
			break;
		case LOADING:
			// 正在载入状态
			pullUpView.clearAnimation();
			loadingView.setVisibility(View.VISIBLE);
			pullUpView.setVisibility(View.INVISIBLE);
			loadingView.startAnimation(refreshingAnimation);
			loadStateTextView.setText(R.string.loading);
			break;
		case DONE:
			// 刷新或载入完毕，啥都不做
			break;
		}
	}

	/**
	 * 不限制上拉或下拉
	 */
	private void releasePull()
	{
		canPullDown = true;
		canPullUp = true;
	}

	/*
	 * （非 Javadoc）由父控件决定是否分发事件，防止事件冲突
	 * 
	 * @see android.view.ViewGroup#dispatchTouchEvent(android.view.MotionEvent)
	 */
	@Override
	public boolean dispatchTouchEvent(MotionEvent ev)
	{
		switch (ev.getActionMasked())
		{
		case MotionEvent.ACTION_DOWN:
			downY = ev.getY();
			lastY = downY;
			timer.cancel();
			mEvents = 0;
			releasePull();
			break;
		case MotionEvent.ACTION_POINTER_DOWN:
		case MotionEvent.ACTION_POINTER_UP:
			// 过滤多点触碰
			mEvents = -1;
			break;
		case MotionEvent.ACTION_MOVE:
			if (mEvents == 0)
			{
				if (((Pullable) pullableView).canPullDown() && canPullDown
						&& state != LOADING)
				{
					// 能够下拉，正在载入时不能下拉
					// 对实际滑动距离做缩小，造成用力拉的感觉
					pullDownY = pullDownY + (ev.getY() - lastY) / radio;
					if (pullDownY < 0)
					{
						pullDownY = 0;
						canPullDown = false;
						canPullUp = true;
					}
					if (pullDownY > getMeasuredHeight())
						pullDownY = getMeasuredHeight();
					if (state == REFRESHING)
					{
						// 正在刷新的时候触摸移动
						isTouch = true;
					}
				} else if (((Pullable) pullableView).canPullUp() && canPullUp
						&& state != REFRESHING)
				{
					// 能够上拉，正在刷新时不能上拉
					pullUpY = pullUpY + (ev.getY() - lastY) / radio;
					if (pullUpY > 0)
					{
						pullUpY = 0;
						canPullDown = true;
						canPullUp = false;
					}
					if (pullUpY < -getMeasuredHeight())
						pullUpY = -getMeasuredHeight();
					if (state == LOADING)
					{
						// 正在载入的时候触摸移动
						isTouch = true;
					}
				} else
					releasePull();
			} else
				mEvents = 0;
			lastY = ev.getY();
			// 依据下拉距离改变比例
			radio = (float) (2 + 2 * Math.tan(Math.PI / 2 / getMeasuredHeight()
					* (pullDownY + Math.abs(pullUpY))));
			requestLayout();
			if (pullDownY <= refreshDist
<span style="white-space:pre">					</span>&& (state == RELEASE_TO_REFRESH || state == DONE)) {
<span style="white-space:pre">				</span>// 假设下拉距离没达到刷新的距离且当前状态是释放刷新，改变状态为下拉刷新
<span style="white-space:pre">				</span>changeState(INIT);
<span style="white-space:pre">			</span>}
<span style="white-space:pre">			</span>if (pullDownY >= refreshDist && (state == INIT || state == DONE)) {
<span style="white-space:pre">				</span>// 假设下拉距离达到刷新的距离且当前状态是初始状态刷新，改变状态为释放刷新
<span style="white-space:pre">				</span>changeState(RELEASE_TO_REFRESH);
<span style="white-space:pre">			</span>}
<span style="white-space:pre">			</span>// 以下是推断上拉载入的，同上，注意pullUpY是负值
<span style="white-space:pre">			</span>if (-pullUpY <= loadmoreDist
<span style="white-space:pre">					</span>&& (state == RELEASE_TO_LOAD || state == DONE)) {
<span style="white-space:pre">				</span>changeState(INIT);
<span style="white-space:pre">			</span>}
<span style="white-space:pre">			</span>if (-pullUpY >= loadmoreDist && (state == INIT || state == DONE)) {
<span style="white-space:pre">				</span>changeState(RELEASE_TO_LOAD);
<span style="white-space:pre">			</span>}
			// 由于刷新和载入操作不能同一时候进行，所以pullDownY和pullUpY不会同一时候不为0，因此这里用(pullDownY +
			// Math.abs(pullUpY))就能够不正确当前状态作区分了
			if ((pullDownY + Math.abs(pullUpY)) > 8)
			{
				// 防止下拉过程中误触发长按事件和点击事件
				ev.setAction(MotionEvent.ACTION_CANCEL);
			}
			break;
		case MotionEvent.ACTION_UP:
			if (pullDownY > refreshDist || -pullUpY > loadmoreDist)
				// 正在刷新时往下拉（正在载入时往上拉），释放后下拉头（上拉头）不隐藏
				isTouch = false;
			if (state == RELEASE_TO_REFRESH)
			{
				changeState(REFRESHING);
				// 刷新操作
				if (mListener != null)
					mListener.onRefresh(this);
			} else if (state == RELEASE_TO_LOAD)
			{
				changeState(LOADING);
				// 载入操作
				if (mListener != null)
					mListener.onLoadMore(this);
			}
			hide();
		default:
			break;
		}
		// 事件分发交给父类
		super.dispatchTouchEvent(ev);
		return true;
	}

	private void initView()
	{
		// 初始化下拉布局
		pullView = refreshView.findViewById(R.id.pull_icon);
		refreshStateTextView = (TextView) refreshView
				.findViewById(R.id.state_tv);
		refreshingView = refreshView.findViewById(R.id.refreshing_icon);
		refreshStateImageView = refreshView.findViewById(R.id.state_iv);
		// 初始化上拉布局
		pullUpView = loadmoreView.findViewById(R.id.pullup_icon);
		loadStateTextView = (TextView) loadmoreView
				.findViewById(R.id.loadstate_tv);
		loadingView = loadmoreView.findViewById(R.id.loading_icon);
		loadStateImageView = loadmoreView.findViewById(R.id.loadstate_iv);
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b)
	{
		if (!isLayout)
		{
			// 这里是第一次进来的时候做一些初始化
			refreshView = getChildAt(0);
			pullableView = getChildAt(1);
			loadmoreView = getChildAt(2);
			isLayout = true;
			initView();
			refreshDist = ((ViewGroup) refreshView).getChildAt(0)
					.getMeasuredHeight();
			loadmoreDist = ((ViewGroup) loadmoreView).getChildAt(0)
					.getMeasuredHeight();
		}
		// 改变子控件的布局，这里直接用(pullDownY + pullUpY)作为偏移量，这样就能够不正确当前状态作区分
		refreshView.layout(0,
				(int) (pullDownY + pullUpY) - refreshView.getMeasuredHeight(),
				refreshView.getMeasuredWidth(), (int) (pullDownY + pullUpY));
		pullableView.layout(0, (int) (pullDownY + pullUpY),
				pullableView.getMeasuredWidth(), (int) (pullDownY + pullUpY)
						+ pullableView.getMeasuredHeight());
		loadmoreView.layout(0,
				(int) (pullDownY + pullUpY) + pullableView.getMeasuredHeight(),
				loadmoreView.getMeasuredWidth(),
				(int) (pullDownY + pullUpY) + pullableView.getMeasuredHeight()
						+ loadmoreView.getMeasuredHeight());
	}

	class MyTimer
	{
		private Handler handler;
		private Timer timer;
		private MyTask mTask;

		public MyTimer(Handler handler)
		{
			this.handler = handler;
			timer = new Timer();
		}

		public void schedule(long period)
		{
			if (mTask != null)
			{
				mTask.cancel();
				mTask = null;
			}
			mTask = new MyTask(handler);
			timer.schedule(mTask, 0, period);
		}

		public void cancel()
		{
			if (mTask != null)
			{
				mTask.cancel();
				mTask = null;
			}
		}

		class MyTask extends TimerTask
		{
			private Handler handler;

			public MyTask(Handler handler)
			{
				this.handler = handler;
			}

			@Override
			public void run()
			{
				handler.obtainMessage().sendToTarget();
			}

		}
	}

	/**
	 * 刷新载入回调接口
	 * 
	 * @author chenjing
	 * 
	 */
	public interface OnRefreshListener
	{
		/**
		 * 刷新操作
		 */
		void onRefresh(PullToRefreshLayout pullToRefreshLayout);

		/**
		 * 载入操作
		 */
		void onLoadMore(PullToRefreshLayout pullToRefreshLayout);
	}

}

上面就是整个布局的代码，并非非常难。

以下看各个View对Pullable接口的实现，ListView和GridView还有ExpandableListView的推断方法是一样的：

PullableListView：

package com.jingchen.pulltorefresh.pullableview;

import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.widget.ListView;

public class PullableListView extends ListView implements Pullable
{

	public PullableListView(Context context)
	{
		super(context);
	}

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

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

	@Override
	public boolean canPullDown()
	{
		if (getCount() == 0)
		{
			// 没有item的时候也能够下拉刷新
			return true;
		} else if (getFirstVisiblePosition() == 0
				&& getChildAt(0).getTop() >= 0)
		{
			// 滑到ListView的顶部了
			return true;
		} else
			return false;
	}

	@Override
	public boolean canPullUp()
	{
		if (getCount() == 0)
		{
			// 没有item的时候也能够上拉载入
			return true;
		} else if (getLastVisiblePosition() == (getCount() - 1))
		{
			// 滑究竟部了
			if (getChildAt(getLastVisiblePosition() - getFirstVisiblePosition()) != null
					&& getChildAt(
							getLastVisiblePosition()
									- getFirstVisiblePosition()).getBottom() <= getMeasuredHeight())
				return true;
		}
		return false;
	}
}

PullableExpandableListView：

package com.jingchen.pulltorefresh.pullableview;

import android.content.Context;
import android.util.AttributeSet;
import android.widget.ExpandableListView;

public class PullableExpandableListView extends ExpandableListView implements
		Pullable
{

	public PullableExpandableListView(Context context)
	{
		super(context);
	}

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

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

	@Override
	public boolean canPullDown()
	{
		if (getCount() == 0)
		{
			// 没有item的时候也能够下拉刷新
			return true;
		} else if (getFirstVisiblePosition() == 0
				&& getChildAt(0).getTop() >= 0)
		{
			// 滑到顶部了
			return true;
		} else
			return false;
	}

	@Override
	public boolean canPullUp()
	{
		if (getCount() == 0)
		{
			// 没有item的时候也能够上拉载入
			return true;
		} else if (getLastVisiblePosition() == (getCount() - 1))
		{
			// 滑究竟部了
			if (getChildAt(getLastVisiblePosition() - getFirstVisiblePosition()) != null
					&& getChildAt(
							getLastVisiblePosition()
									- getFirstVisiblePosition()).getBottom() <= getMeasuredHeight())
				return true;
		}
		return false;
	}

}

PullableGridView：

package com.jingchen.pulltorefresh.pullableview;

import android.content.Context;
import android.util.AttributeSet;
import android.widget.GridView;

public class PullableGridView extends GridView implements Pullable
{

	public PullableGridView(Context context)
	{
		super(context);
	}

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

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

	@Override
	public boolean canPullDown()
	{
		if (getCount() == 0)
		{
			// 没有item的时候也能够下拉刷新
			return true;
		} else if (getFirstVisiblePosition() == 0
				&& getChildAt(0).getTop() >= 0)
		{
			// 滑到顶部了
			return true;
		} else
			return false;
	}

	@Override
	public boolean canPullUp()
	{
		if (getCount() == 0)
		{
			// 没有item的时候也能够上拉载入
			return true;
		} else if (getLastVisiblePosition() == (getCount() - 1))
		{
			// 滑究竟部了
			if (getChildAt(getLastVisiblePosition() - getFirstVisiblePosition()) != null
					&& getChildAt(
							getLastVisiblePosition()
									- getFirstVisiblePosition()).getBottom() <= getMeasuredHeight())
				return true;
		}
		return false;
	}

}

PullableScrollView：

package com.jingchen.pulltorefresh.pullableview;

import android.content.Context;
import android.util.AttributeSet;
import android.widget.ScrollView;

public class PullableScrollView extends ScrollView implements Pullable
{

	public PullableScrollView(Context context)
	{
		super(context);
	}

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

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

	@Override
	public boolean canPullDown()
	{
		if (getScrollY() == 0)
			return true;
		else
			return false;
	}

	@Override
	public boolean canPullUp()
	{
		if (getScrollY() >= (getChildAt(0).getHeight() - getMeasuredHeight()))
			return true;
		else
			return false;
	}

}

PullableWebView：

package com.jingchen.pulltorefresh.pullableview;

import android.content.Context;
import android.util.AttributeSet;
import android.webkit.WebView;

public class PullableWebView extends WebView implements Pullable
{

	public PullableWebView(Context context)
	{
		super(context);
	}

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

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

	@Override
	public boolean canPullDown()
	{
		if (getScrollY() == 0)
			return true;
		else
			return false;
	}

	@Override
	public boolean canPullUp()
	{
		if (getScrollY() >= getContentHeight() * getScale()
				- getMeasuredHeight())
			return true;
		else
			return false;
	}
}

ImageView和TextView就不贴了，我直接在方法里返回了true。

OK了，整个demo的代码有点多，就不贴了。

源代码下载