ListView下拉刷新，上拉自动加载更多

下拉刷新，Android中非常普遍的功能。为了方便便重写的ListView来实现下拉刷新，同时添加了上拉自动加载更多的功能。设计最初是参考开源中国的Android客户端源码。先看示例图。

        

                                                  图1                                                                                                             图2

        

                                                  图3                                                                                                            图4

         

                                                  图5                                                                                                       图6

下拉刷新的时动画效果: 图1 ==》 图2 ==》 图3 ==》 图4 ==》 图1。

上拉自动加载更多的效果：图5

图6是示例demo的截图

重写后的listview动画效果来源于添加的头部（header）和尾部（footer），listview提供了addHeaderView和addFooterView方法来添加header和footer。大家也可以通过修改头部、尾部的xml文件来定义自己的动画效果。

实现原理

1.下拉刷新

通过onTouchEvent判断手势，来改变listview的header。header的状态共4种，自己定义为：

NONE（对应图1）：初始状态

PULL（对应图2）：下拉状态，此时松开会还原到状态NONE，并不进行刷新

RELEASE（对应图3）：同样是下拉状态，但此刻松开会执行刷新，进入状态REFRESHING

REFRESHING（对应图4）：正在执行刷新，刷新结束后进入状态NONE。

header在四种状态切换时不仅改变内部组件，同时改变自身的大小。改变内部组件的体现比如，箭头的朝上或者朝下，文字提示的变化，等待圆圈的显示与否。大小的改变其实就是高度的改变，NONE时header高度为0,RELEASE时header的高度由你下拉的程度决定。

2.加载更多

在listview滑动停止后，判断listview的最后一个item是否已经显示，如果显示说明listview已经滑动到了最底部，这时便触发加载更多的方法，方法结束根据结果改变footer。

3.回调方法

在类中定义了两个接口OnRefreshListener和OnLoadListener，用来定义和提供加载数据的方法，具体实现则交给它们的实现类去做。

示例代码

AutoListView.java

 package com.example.autolistview.widget;

 import com.example.autolistview.R;
 import com.example.autolistview.utils.Utils;

 import android.content.Context;
 import android.util.AttributeSet;
 import android.view.LayoutInflater;
 import android.view.MotionEvent;
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.animation.LinearInterpolator;
 import android.view.animation.RotateAnimation;
 import android.widget.AbsListView;
 import android.widget.ImageView;
 import android.widget.ProgressBar;
 import android.widget.TextView;
 import android.widget.AbsListView.OnScrollListener;
 import android.widget.ListView;

 /**
  * @author SunnyCoffee
  * @create 2013-10-24
  * @version 1.0
  * @desc 自定义Listview　下拉刷新,上拉加载更多
  */

 public class AutoListView extends ListView implements OnScrollListener {

     // 区分当前操作是刷新还是加载
     public static final int REFRESH = 0;
     public static final int LOAD = 1;

     // 区分PULL和RELEASE的距离的大小
     private static final int SPACE = 20;

     // 定义header的四种状态和当前状态
     private static final int NONE = 0;
     private static final int PULL = 1;
     private static final int RELEASE = 2;
     private static final int REFRESHING = 3;
     private int state;

     private LayoutInflater inflater;
     private View header;
     private View footer;
     private TextView tip;
     private TextView lastUpdate;
     private ImageView arrow;
     private ProgressBar refreshing;

     private TextView noData;
     private TextView loadFull;
     private TextView more;
     private ProgressBar loading;

     private RotateAnimation animation;
     private RotateAnimation reverseAnimation;

     private int startY;

     private int firstVisibleItem;
     private int scrollState;
     private int headerContentInitialHeight;
     private int headerContentHeight;

     // 只有在listview第一个item显示的时候（listview滑到了顶部）才进行下拉刷新， 否则此时的下拉只是滑动listview
     private boolean isRecorded;
     private boolean isLoading;// 判断是否正在加载
     private boolean loadEnable = true;// 开启或者关闭加载更多功能
     private boolean isLoadFull;
     private int pageSize = 10;

     private OnRefreshListener onRefreshListener;
     private OnLoadListener onLoadListener;

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

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

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

     // 下拉刷新监听
     public void setOnRefreshListener(OnRefreshListener onRefreshListener) {
         this.onRefreshListener = onRefreshListener;
     }

     // 加载更多监听
     public void setOnLoadListener(OnLoadListener onLoadListener) {
         this.loadEnable = true;
         this.onLoadListener = onLoadListener;
     }

     public boolean isLoadEnable() {
         return loadEnable;
     }

     // 这里的开启或者关闭加载更多，并不支持动态调整
     public void setLoadEnable(boolean loadEnable) {
         this.loadEnable = loadEnable;
         this.removeFooterView(footer);
     }

     public int getPageSize() {
         return pageSize;
     }

     public void setPageSize(int pageSize) {
         this.pageSize = pageSize;
     }

     // 初始化组件
     private void initView(Context context) {

         // 设置箭头特效
         animation = new RotateAnimation(0, -180,
                 RotateAnimation.RELATIVE_TO_SELF, 0.5f,
                 RotateAnimation.RELATIVE_TO_SELF, 0.5f);
         animation.setInterpolator(new LinearInterpolator());
         animation.setDuration(100);
         animation.setFillAfter(true);

         reverseAnimation = new RotateAnimation(-180, 0,
                 RotateAnimation.RELATIVE_TO_SELF, 0.5f,
                 RotateAnimation.RELATIVE_TO_SELF, 0.5f);
         reverseAnimation.setInterpolator(new LinearInterpolator());
         reverseAnimation.setDuration(100);
         reverseAnimation.setFillAfter(true);

         inflater = LayoutInflater.from(context);
         footer = inflater.inflate(R.layout.listview_footer, null);
         loadFull = (TextView) footer.findViewById(R.id.loadFull);
         noData = (TextView) footer.findViewById(R.id.noData);
         more = (TextView) footer.findViewById(R.id.more);
         loading = (ProgressBar) footer.findViewById(R.id.loading);

         header = inflater.inflate(R.layout.pull_to_refresh_header, null);
         arrow = (ImageView) header.findViewById(R.id.arrow);
         tip = (TextView) header.findViewById(R.id.tip);
         lastUpdate = (TextView) header.findViewById(R.id.lastUpdate);
         refreshing = (ProgressBar) header.findViewById(R.id.refreshing);

         // 为listview添加头部和尾部，并进行初始化
         headerContentInitialHeight = header.getPaddingTop();
         measureView(header);
         headerContentHeight = header.getMeasuredHeight();
         topPadding(-headerContentHeight);
         this.addHeaderView(header);
         this.addFooterView(footer);
         this.setOnScrollListener(this);
     }

     public void onRefresh() {
         if (onRefreshListener != null) {
             onRefreshListener.onRefresh();
         }
     }

     public void onLoad() {
         if (onLoadListener != null) {
             onLoadListener.onLoad();
         }
     }

     public void onRefreshComplete(String updateTime) {
         lastUpdate.setText(this.getContext().getString(R.string.lastUpdateTime,
                 lastUpdate));
         state = NONE;
         refreshHeaderViewByState();
     }

     // 用于下拉刷新结束后的回调
     public void onRefreshComplete() {
         String currentTime = Utils.getCurrentTime();
         onRefreshComplete(currentTime);
     }

     // 用于加载更多结束后的回调
     public void onLoadComplete() {
         isLoading = false;
     }

     @Override
     public void onScroll(AbsListView view, int firstVisibleItem,
             int visibleItemCount, int totalItemCount) {
         this.firstVisibleItem = firstVisibleItem;
     }

     @Override
     public void onScrollStateChanged(AbsListView view, int scrollState) {
         this.scrollState = scrollState;
         ifNeedLoad(view, scrollState);
     }

     // 根据listview滑动的状态判断是否需要加载更多
     private void ifNeedLoad(AbsListView view, int scrollState) {
         if (!loadEnable) {
             return;
         }
         try {
             if (scrollState == OnScrollListener.SCROLL_STATE_IDLE
                     && !isLoading
                     && view.getLastVisiblePosition() == view
                             .getPositionForView(footer) && !isLoadFull) {
                 onLoad();
                 isLoading = true;
             }
         } catch (Exception e) {
         }
     }

     /**
      * 监听触摸事件，解读手势
      */
     @Override
     public boolean onTouchEvent(MotionEvent ev) {
         switch (ev.getAction()) {
         case MotionEvent.ACTION_DOWN:
             if (firstVisibleItem == 0) {
                 isRecorded = true;
                 startY = (int) ev.getY();
             }
             break;
         case MotionEvent.ACTION_CANCEL:
         case MotionEvent.ACTION_UP:
             if (state == PULL) {
                 state = NONE;
                 refreshHeaderViewByState();
             } else if (state == RELEASE) {
                 state = REFRESHING;
                 refreshHeaderViewByState();
                 onRefresh();
             }
             isRecorded = false;
             break;
         case MotionEvent.ACTION_MOVE:
             whenMove(ev);
             break;
         }
         return super.onTouchEvent(ev);
     }

     // 解读手势，刷新header状态
     private void whenMove(MotionEvent ev) {
         if (!isRecorded) {
             return;
         }
         int tmpY = (int) ev.getY();
         int space = tmpY - startY;
         int topPadding = space - headerContentHeight;
         switch (state) {
         case NONE:
             if (space > 0) {
                 state = PULL;
                 refreshHeaderViewByState();
             }
             break;
         case PULL:
             topPadding(topPadding);
             if (scrollState == SCROLL_STATE_TOUCH_SCROLL
                     && space > headerContentHeight + SPACE) {
                 state = RELEASE;
                 refreshHeaderViewByState();
             }
             break;
         case RELEASE:
             topPadding(topPadding);
             if (space > 0 && space < headerContentHeight + SPACE) {
                 state = PULL;
                 refreshHeaderViewByState();
             } else if (space <= 0) {
                 state = NONE;
                 refreshHeaderViewByState();
             }
             break;
         }

     }

     // 调整header的大小。其实调整的只是距离顶部的高度。
     private void topPadding(int topPadding) {
         header.setPadding(header.getPaddingLeft(), topPadding,
                 header.getPaddingRight(), header.getPaddingBottom());
         header.invalidate();
     }

     /**
      * 这个方法是根据结果的大小来决定footer显示的。
      *
      * 这里假定每次请求的条数为10。如果请求到了10条。则认为还有数据。如过结果不足10条，则认为数据已经全部加载，这时footer显示已经全部加载
      *
      *
      * @param resultSize
      */
     public void setResultSize(int resultSize) {
         if (resultSize == 0) {
             isLoadFull = true;
             loadFull.setVisibility(View.GONE);
             loading.setVisibility(View.GONE);
             more.setVisibility(View.GONE);
             noData.setVisibility(View.VISIBLE);
         } else if (resultSize > 0 && resultSize < pageSize) {
             isLoadFull = true;
             loadFull.setVisibility(View.VISIBLE);
             loading.setVisibility(View.GONE);
             more.setVisibility(View.GONE);
             noData.setVisibility(View.GONE);
         } else if (resultSize == pageSize) {
             isLoadFull = false;
             loadFull.setVisibility(View.GONE);
             loading.setVisibility(View.VISIBLE);
             more.setVisibility(View.VISIBLE);
             noData.setVisibility(View.GONE);
         }

     }

     // 根据当前状态，调整header
     private void refreshHeaderViewByState() {
         switch (state) {
         case NONE:
             topPadding(-headerContentHeight);
             tip.setText(R.string.pull_to_refresh);
             refreshing.setVisibility(View.GONE);
             arrow.clearAnimation();
             arrow.setImageResource(R.drawable.pull_to_refresh_arrow);
             break;
         case PULL:
             arrow.setVisibility(View.VISIBLE);
             tip.setVisibility(View.VISIBLE);
             lastUpdate.setVisibility(View.VISIBLE);
             refreshing.setVisibility(View.GONE);
             tip.setText(R.string.pull_to_refresh);
             arrow.clearAnimation();
             arrow.setAnimation(reverseAnimation);
             break;
         case RELEASE:
             arrow.setVisibility(View.VISIBLE);
             tip.setVisibility(View.VISIBLE);
             lastUpdate.setVisibility(View.VISIBLE);
             refreshing.setVisibility(View.GONE);
             tip.setText(R.string.pull_to_refresh);
             tip.setText(R.string.release_to_refresh);
             arrow.clearAnimation();
             arrow.setAnimation(animation);
             break;
         case REFRESHING:
             topPadding(headerContentInitialHeight);
             refreshing.setVisibility(View.VISIBLE);
             arrow.clearAnimation();
             arrow.setVisibility(View.GONE);
             tip.setVisibility(View.GONE);
             lastUpdate.setVisibility(View.GONE);
             break;
         }
     }

     // 用来计算header大小的。比较隐晦。
     private void measureView(View child) {
         ViewGroup.LayoutParams p = child.getLayoutParams();
         if (p == null) {
             p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                     ViewGroup.LayoutParams.WRAP_CONTENT);
         }
         int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0, p.width);
         int lpHeight = p.height;
         int childHeightSpec;
         if (lpHeight > 0) {
             childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight,
                     MeasureSpec.EXACTLY);
         } else {
             childHeightSpec = MeasureSpec.makeMeasureSpec(0,
                     MeasureSpec.UNSPECIFIED);
         }
         child.measure(childWidthSpec, childHeightSpec);
     }

     /*
      * 定义下拉刷新接口
      */
     public interface OnRefreshListener {
         public void onRefresh();
     }

     /*
      * 定义加载更多接口
      */
     public interface OnLoadListener {
         public void onLoad();
     }

 }

这个类的逻辑复杂的地方就是header四种状态的判断和切换。

以下是几种状态的切换情况

NONE   ==》 PULL

NONE 《==   PULL   ==》 RELEASE

PULL 《==   RELEASE   ==》 REFRESHING

REFRESHING   ==》 NONE

代码中对于 RELEASE  ==》PULL 状态的切换处理的不太理想，好像是纵坐标的记录方式有问题，如果有谁解决，希望能够留言告知。

为了减少篇幅，其他代码就不在贴了。

注意：定义header的xml最外层必须使用线性布局，不然的话会出错。

 

测试代码：点击下载（eclipse工程项目，编码UTF-8）