Android下拉刷新上拉加载控件(适用于所有View）

     前面写过一篇关于下拉刷新控件的文章下拉刷新控件终结者：PullToRefreshLayout，后来看到好多人还有上拉加载更多的需求，于是就在前面下拉刷新控件的基础上进行了改进，加了上拉加载的功能。不仅如此，我已经把它改成了对所有View都通用！可以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的下拉刷新和上拉加载。后面会提供demo的下载地址，最新代码已上传到GitHub：https://github.com/jinGChenUSTC/PullToRefreshAndLoad

依照惯例，下面将会是一大波效果图：

demo首页也是可下拉的ListView，在底下可以加入table：

                                            

ListView：

                

GridView：

                

ExpandableListView：

                

ScrollView：

               

WebView：

               

ImageView：

                

TextView：

                

很不错吧？最后的ImageView和TextView是最简单的，直接在下面的接口方法里返回true。
增加上拉加载很简单，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需要统一一下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 
{ 
     
    boolean canPullDown(); 
 
     
    boolean canPullUp(); 
} 
从接口名就可以看出它是一个提供判断是否可拉的方法的接口。这个接口的两个方法，canPullDown()是判断何时可以下拉的方法，canPullUp()则是判断何时可以上拉，我在demo中的判断是滑到顶部的时候可以下拉，滑到底部的时候可以上拉。所有需要上拉和下拉的View都需要实现这个接口。后面会给出一些View的实现。先来看看改进后的自定义的布局PullToRefreshLayout，增加了一个上拉头，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，这里有改动的需要注意的地方如下：
1、增加了上拉头，相应的也增加了控制变量。

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，让使用者可以更加自由的设置监听器。

这个PullToRefreshLayout只负责管理三个控件，如果一个View需要有上拉下拉功能则只需实现接口就行了。下面看PullToRefreshLayout的代码，注释写了好多：

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; 
 
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; 
 // 释放加载 
 public static final int RELEASE_TO_LOAD = 3; 
 // 正在加载 
 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不可能同时不为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; 
 // 释放加载的距离 
 private float loadmoRedist = 200; 
 private MyTimer timer; 
 // 回滚速度 
 public float MOVE_SPEED = 8; 
 // 第一次执行布局 
 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; 
 // 正在加载的图标 
 private View loadingView; 
 // 加载结果图标 
 private View loadStateImageView; 
 // 加载结果：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，如果不加控制，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; 
  
 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) 
 { 
 // 已完成回弹 
 pullDownY = 0; 
 pullView.clearAnimation(); 
 // 隐藏下拉头时有可能还在刷新，只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) 
 { 
 // 已完成回弹 
 pullUpY = 0; 
 pullUpView.clearAnimation(); 
 // 隐藏下拉头时有可能还在刷新，只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); 
 // 添加匀速转动动画 
 LinearInterpolator lir = new LinearInterpolator(); 
 rotateAnimation.setInterpolator(lir); 
 refreshingAnimation.setInterpolator(lir); 
 } 
 private void hide() 
 { 
 timer.schedule(5); 
 } 
  
  
 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); 
 } 
  
 public void loadmoreFinish(int refreshResult) 
 { 
 loadingView.clearAnimation(); 
 loadingView.setVisibility(View.GONE); 
 switch (refreshResult) 
 { 
 case SUCCEED: 
 // 加载成功 
 loadStateImageView.setVisibility(View.VISIBLE); 
 loadStateTextView.setText(R.string.load_succeed); 
 loadStateImageView.setBackgroundResource(R.drawable.load_succeed); 
 break; 
 case FAIL: 
 default: 
 // 加载失败 
 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: 
 // 释放加载状态 
 loadStateTextView.setText(R.string.release_to_load); 
 pullUpView.startAnimation(rotateAnimation); 
 break; 
 case LOADING: 
 // 正在加载状态 
 pullUpView.clearAnimation(); 
 loadingView.setVisibility(View.VISIBLE); 
 pullUpView.setVisibility(View.INVISIBLE); 
 loadingView.startAnimation(refreshingAnimation); 
 loadStateTextView.setText(R.string.loading); 
 break; 
 case DONE: 
 // 刷新或加载完毕，啥都不做 
 break; 
 } 
 } 
  
 private void releasePull() 
 { 
 canPullDown = true; 
 canPullUp = true; 
 } 
  
 @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) 
 { 
  // 可以下拉，正在加载时不能下拉 
  // 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) 
 { 
  // 可以上拉，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) 
  { 
  // 正在加载的时候触摸移动 
  isTouch = true; 
  } 
 } else 
  releasePull(); 
 } else 
 mEvents = 0; 
 lastY = ev.getY(); 
 // 根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>// 如果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>// 如果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>// 下面是判断上拉加载的，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>} 
 // 因为刷新和加载操作不能同时进行，所以pullDownY和pullUpY不会同时不为0，因此这里用(pullDownY + 
 // Math.abs(pullUpY))就可以不对当前状态作区分了 
 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（正在加载时往上拉），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); 
 // 加载操作 
 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，这样就可以不对当前状态作区分 
 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(); 
 } 
 } 
 } 
  
 public interface OnRefreshListener 
 { 
  
 void onRefresh(PullToRefreshLayout pullToRefreshLayout); 
  
 void onLoadMore(PullToRefreshLayout pullToRefreshLayout); 
 } 
} 

上面就是整个布局的代码，并不是很难。
下面看各个View对Pullable接口的实现，ListView和GridView还有ExpandableListView的判断方法是一样的：
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的时候也可以下拉刷新 
 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的时候也可以上拉加载 
 return true; 
 } else if (getLastVisiblePosition() == (getCount() - 1)) 
 { 
 // 滑到底部了 
 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的时候也可以下拉刷新 
 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的时候也可以上拉加载 
 return true; 
 } else if (getLastVisiblePosition() == (getCount() - 1)) 
 { 
 // 滑到底部了 
 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的时候也可以下拉刷新 
 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的时候也可以上拉加载 
 return true; 
 } else if (getLastVisiblePosition() == (getCount() - 1)) 
 { 
 // 滑到底部了 
 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。
源码下载：通用版下拉刷新上拉加载大合集demo 

精彩专题分享：javascriptAndroid加载功能汇总

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希望本文所述对大家学习Android下拉刷新上拉加载控件有所帮助。

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