继承ListView，自定义下拉刷新功能

一，自定义一个类，继承ListView。代码如下：

package com.example.view;

import com.example.text.R;

import android.content.Context;
import android.widget.AbsListView;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.PopupWindow;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.support.v4.widget.SwipeRefreshLayout.OnRefreshListener;
import android.util.AttributeSet;
import android.util.Log;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewConfiguration;
import android.view.animation.LinearInterpolator;
import android.view.animation.RotateAnimation;

/**
 * 下拉刷新，上拉自动加载的自定义view,增加滑动删除功能
 * @author Administrator
 *
 */
public class PullToFlashView extends ListView implements OnScrollListener,OnClickListener{
    /**
     * 下拉状态
     * @param context
     */
     private static final int PULL_TO_REFRESH = 1;   //下拉-默认为初始状态  准备下拉刷新
     private static final int RELEASE_TO_REFRESH = 2;   //释放刷新
     private static final int REFRESHING = 3;       //正在刷新

     private static final String TAG = "PullRefreshListView";

     private OnRefreshListener mOnRefreshListener;

     /**
     * 组件滑动监听器 scroll  当view在进行下拉滑动的时候，判断滑动的距离，
     * 如果达到可以进行刷新的临界点时候，回调当前接口中的方法
     * Listener that will receive notifications every time the list scrolls.
     */
     private OnScrollListener mOnScrollListener;

    //下拉刷新的的头部view
    private LinearLayout mRefreshView;
    private ImageView mRefreshViewImage;
    private ProgressBar mRefreshViewProgress;
    private TextView mRefreshViewText;//文字提醒
    private TextView mRefreshViewLastUpdated;//时间更新

    private int mRefreshState;
    private int mCurrentScrollState;

    private RotateAnimation mFlipAnimation; //旋转动画
    private RotateAnimation mReverseFlipAnimation;

    private int mRefreshViewHeight;
    private int mRefreshOriginalTopPadding;
    private int mLastMotionY;



    public PullToFlashView(Context context) {
        super(context);
        init(context);

    }




    public PullToFlashView(Context context, AttributeSet attrs) {
     super(context, attrs);
     init(context);

     }
    private void init(Context context) {
         mFlipAnimation = new RotateAnimation(0, -180,
                    RotateAnimation.RELATIVE_TO_SELF, 0.5f,
                    RotateAnimation.RELATIVE_TO_SELF, 0.5f);
            mFlipAnimation.setInterpolator(new LinearInterpolator());
            mFlipAnimation.setDuration(250);
            mFlipAnimation.setFillAfter(true);
            mReverseFlipAnimation = new RotateAnimation(-180, 0,
                    RotateAnimation.RELATIVE_TO_SELF, 0.5f,
                    RotateAnimation.RELATIVE_TO_SELF, 0.5f);
            mReverseFlipAnimation.setInterpolator(new LinearInterpolator());
            mReverseFlipAnimation.setDuration(250);
            mReverseFlipAnimation.setFillAfter(true);

            mRefreshView = (LinearLayout) View.inflate(context, R.layout.pull_to_refresh_header, null);
            mRefreshViewText = (TextView) mRefreshView.findViewById(R.id.pull_to_refresh_text);
            mRefreshViewImage = (ImageView) mRefreshView.findViewById(R.id.pull_to_refresh_image);
            mRefreshViewProgress = (ProgressBar) mRefreshView.findViewById(R.id.pull_to_refresh_progress);
            mRefreshViewLastUpdated = (TextView) mRefreshView.findViewById(R.id.pull_to_refresh_updated_at);

            mRefreshState = PULL_TO_REFRESH;
            mRefreshViewImage.setMinimumHeight(50); //设置下拉最小的高度为50

            setFadingEdgeLength(0);
            setHeaderDividersEnabled(false);

            //把refreshview加入到listview的头部
            addHeaderView(mRefreshView);
            super.setOnScrollListener(this);
            mRefreshView.setOnClickListener(this);

            mRefreshView.measure(MeasureSpec.UNSPECIFIED, MeasureSpec.UNSPECIFIED);
            mRefreshViewHeight = mRefreshView.getMeasuredHeight();
            mRefreshOriginalTopPadding = -mRefreshViewHeight;

            resetHeaderPadding();
    }
    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        int action = ev.getAction();  
        int x = (int) ev.getX();  
        int y = (int) ev.getY();  


        return super.dispatchTouchEvent(ev);
    }






      /**
     * Set the listener that will receive notifications every time the list scrolls.
     * 
     * @param l  The scroll listener.
     */
    @Override
    public void setOnScrollListener(OnScrollListener l) {
        mOnScrollListener = l;
    }

    /**
     * 注册listview下拉刷新回到接口
     * Register a callback to be invoked when this list should be refreshed.
     * 
     * @param onRefreshListener  The callback to run.
     */
    public void setOnRefreshListener(OnRefreshListener onRefreshListener) {
        mOnRefreshListener = onRefreshListener;
    }

    /**
     * 进行设置设置上一次更新的时候
     *
    * Set a text to represent when the list was last updated. 
    * @param lastUpdated Last updated at.
    */
   public void setLastUpdated(CharSequence lastUpdated) {
       if (lastUpdated != null) {
           mRefreshViewLastUpdated.setVisibility(View.VISIBLE);
           mRefreshViewLastUpdated.setText(lastUpdated);
       } else {
           mRefreshViewLastUpdated.setVisibility(View.GONE);
       }
   }

   /**
    * touch事件处理
    * @param event
    * @return
    */
   @Override
   public boolean onTouchEvent(MotionEvent event) {

       final int y = (int) event.getY();
       switch (event.getAction()) {
       case MotionEvent.ACTION_DOWN:
           mLastMotionY = y;
           break;
       case MotionEvent.ACTION_MOVE:
           int offsetY = (int) event.getY();
           int deltY = Math.round(offsetY - mLastMotionY);
           mLastMotionY = offsetY;

           if (getFirstVisiblePosition() == 0 && mRefreshState != REFRESHING) {
               deltY = deltY / 2;
               mRefreshOriginalTopPadding += deltY;
               if (mRefreshOriginalTopPadding < -mRefreshViewHeight) {
                   mRefreshOriginalTopPadding = -mRefreshViewHeight;
               }
               resetHeaderPadding();
           }
           break;
       case MotionEvent.ACTION_UP:
           //当手指抬开得时候 进行判断下拉的距离 ，如果>=临界值，那么进行刷洗，否则回归原位
           if (!isVerticalScrollBarEnabled()) {
               setVerticalScrollBarEnabled(true);
           }
           if (getFirstVisiblePosition() == 0 && mRefreshState != REFRESHING) {
               if (mRefreshView.getBottom() >= mRefreshViewHeight 
                       && mRefreshState == RELEASE_TO_REFRESH) {
                   //准备开始刷新
                   prepareForRefresh();
               } else {
                   // Abort refresh
                   resetHeader();
               }
           }
           break;
       }
       return super.onTouchEvent(event);
   }

   @Override
   public void onScroll(AbsListView view, int firstVisibleItem,
           int visibleItemCount, int totalItemCount) {
       if (mCurrentScrollState == SCROLL_STATE_TOUCH_SCROLL && mRefreshState != REFRESHING) {
            if (firstVisibleItem == 0) {
               if ((mRefreshView.getBottom() >= mRefreshViewHeight)
                       && mRefreshState != RELEASE_TO_REFRESH) {
                   mRefreshViewText.setText(R.string.pull_to_refresh_release_label_it);
                   mRefreshViewImage.clearAnimation();
                   mRefreshViewImage.startAnimation(mFlipAnimation);
                   mRefreshState = RELEASE_TO_REFRESH;
               } else if (mRefreshView.getBottom() < mRefreshViewHeight
                       && mRefreshState != PULL_TO_REFRESH) {
                   mRefreshViewText.setText(R.string.pull_to_refresh_pull_label_it);
                   mRefreshViewImage.clearAnimation();
                   mRefreshViewImage.startAnimation(mReverseFlipAnimation);
                   mRefreshState = PULL_TO_REFRESH;
               }
           }
       }

       if (mOnScrollListener != null) {
           mOnScrollListener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount);
       }
   }

   @Override
   public void onScrollStateChanged(AbsListView view, int scrollState) {
       mCurrentScrollState = scrollState;

       if (mOnScrollListener != null) {
           mOnScrollListener.onScrollStateChanged(view, scrollState);
       }
   }

   /**
    * Sets the header padding back to original size.
    */
   private void resetHeaderPadding() {
       mRefreshView.setPadding(
               mRefreshView.getPaddingLeft(),
               mRefreshOriginalTopPadding,
               mRefreshView.getPaddingRight(),
               mRefreshView.getPaddingBottom());
   }

   public void prepareForRefresh() {
       if (mRefreshState != REFRESHING) {
           mRefreshState = REFRESHING;

           mRefreshOriginalTopPadding = 0;
           resetHeaderPadding();

           mRefreshViewImage.clearAnimation();
           mRefreshViewImage.setVisibility(View.GONE);
           mRefreshViewProgress.setVisibility(View.VISIBLE);
           mRefreshViewText.setText(R.string.pull_to_refresh_refreshing_label_it);

           onRefresh();
       }
   }

   private void resetHeader() {
       mRefreshState = PULL_TO_REFRESH;

       mRefreshOriginalTopPadding = -mRefreshViewHeight;
       resetHeaderPadding();

       mRefreshViewImage.clearAnimation();
       mRefreshViewImage.setVisibility(View.VISIBLE);
       mRefreshViewProgress.setVisibility(View.GONE);
       mRefreshViewText.setText(R.string.pull_to_refresh_pull_label_it);
   }
   /**
    * 开始回调刷新
    */
   public void onRefresh() {
       if (mOnRefreshListener != null) {
           mOnRefreshListener.onRefresh();
       }
   }

   /**
    * Resets the list to a normal state after a refresh.
    */
   public void onRefreshComplete() {        
       Log.d(TAG, "onRefreshComplete");

       resetHeader();
   }

   @Override
   public void onClick(View v) {
       Log.d(TAG, "onClick");
   }

   /**
    * Interface definition for a callback to be invoked when list should be
    * refreshed.
    */
   public interface OnRefreshListener {
       /**
        * Called when the list should be refreshed.
        * <p>
        * A call to {@link PullToRefreshListView #onRefreshComplete()} is
        * expected to indicate that the refresh has completed.
        */
       public void onRefresh();
   }





}

上面所说的头布局（R.layout.pull_to_refresh_header）XML资源文件如下:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/pull_to_refresh_header"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:background="#F3F3F3"
    android:orientation="vertical" >
    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingTop="23dip" >
        <LinearLayout
            android:id="@+id/pull_to_refresh_view"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:orientation="vertical" >
            <TextView
                android:id="@+id/pull_to_refresh_text"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:gravity="center"
                android:text="@string/pull_to_refresh_pull_label"
                android:textColor="#777777"
                android:textSize="16sp" />
            <TextView
                android:id="@+id/pull_to_refresh_updated_at"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:gravity="center"
                android:text="@string/pull_to_refresh_updated_at"
                android:textColor="#999999"
                android:textSize="14sp" />
        </LinearLayout>
        <ProgressBar
            android:id="@+id/pull_to_refresh_progress"
            android:layout_width="30dip"
            android:layout_height="30dip"
            android:layout_marginRight="22dip"
            android:layout_marginTop="5dip"
            android:layout_toLeftOf="@+id/pull_to_refresh_view"
            android:indeterminate="true"
            android:indeterminateDrawable="@drawable/ic_loading_refresh"
            android:visibility="gone" />
        <ImageView
            android:id="@+id/pull_to_refresh_image"
            android:layout_width="32dip"
            android:layout_height="32dip"
            android:layout_marginRight="20dip"
            android:layout_marginTop="5dip"
            android:layout_toLeftOf="@+id/pull_to_refresh_view"
            android:contentDescription="@string/app_name"
            android:gravity="center"
            android:src="@drawable/ic_refresh_down" />
    </RelativeLayout>
    <View
        android:layout_width="fill_parent"
        android:layout_height="15dip" />
</LinearLayout

这里要说明一下，上面Xml文件里面的ProgressBar利用的是旋转动画实现的，其实现过程如下：
自定义一个xml布局 ic_loading_refresh，放在drawable文件夹下，里面drawable属性对应的图片资源(ic_loading)自定义即可

<?xml version="1.0" encoding="utf-8"?>
<rotate xmlns:android="http://schemas.android.com/apk/res/android"
    android:drawable="@drawable/ic_loading"
    android:fromDegrees="0"
    android:pivotX="50%"
    android:pivotY="50%"
    android:toDegrees="360" />

自定义的view写好了，接着就是在Activity中实现啦

public class PullListviewActivity extends Activity {
    /**
     * 数据源
     */
    private List<String> mTitles;
    /**
     * 适配器
     */
    private PullAdapter mPullAdapter;
    /**
     * 下拉刷新的listview
     */
    private PullToFlashView mPullToFlashView;

    private LayoutInflater mLayoutInflater;

    private View load_more;
    private TextView load_more_tv; // listview底部加载view 显示数据
    private ProgressBar load_more_progress; // listview底部加载view 显示进度
    private LinearLayout load_next_page_layout;
    private Handler newHandler=new Handler()
    {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            if(msg.what==1){
                refreshTitles();
                UIUtils.savePullToRefreshLastUpdateAt(mPullToFlashView,UIUtils.DEMO_PULL_TIME_KEY);
                //刷新view
                mPullAdapter.notifyDataSetChanged();
                //刷新完成
                mPullToFlashView.onRefreshComplete();
            }else if(msg.what==2){
                moreTitles();
                //刷新view
                mPullAdapter.notifyDataSetChanged();
                //showToastMsgShort("加载更多数据成功...");
                load_more_tv.setText("数据加载完成");
            }

        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_pull_listview);
        //
        mLayoutInflater= getLayoutInflater();
        //初始化组件
        mPullToFlashView = (PullToFlashView) findViewById(R.id.lv_pull_item);

         //特别注意 里边的view的控件可以根据当前的状态 修改字符串信息
        load_more = mLayoutInflater.inflate(R.layout.load_more_footview_layout,
                null);
       load_more_tv = (TextView) load_more
                .findViewById(R.id.load_next_page_text);
        load_more_progress = (ProgressBar) load_more
                .findViewById(R.id.load_next_page_progress);
        load_next_page_layout = (LinearLayout) load_more
                .findViewById(R.id.load_next_page_layout);
        //listview添加尾部 上拉加载更多view
        mPullToFlashView.addFooterView(load_more, null, false);
        load_more_tv.setText("上拉加载更多数据...");

        initTitles();
        //初始化 上次下拉刷新的时间
       UIUtils.setPullToRefreshLastUpdated(mPullToFlashView,UIUtils.DEMO_PULL_TIME_KEY,this);
        mPullAdapter=new PullAdapter();
        mPullToFlashView.setAdapter(mPullAdapter);
        //listview item点击事件处理
        mPullToFlashView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

            }
        });

        //listview 开始下拉刷新回调函数
        mPullToFlashView.setOnRefreshListener(new PullToFlashView.OnRefreshListener() {

            @Override
            public void onRefresh() {

                //进行加载数据
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            Thread.sleep(5000);
                            newHandler.sendEmptyMessage(1);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }

                    }
                }).start();
            }
            }
        );

        //listview 滑动  进行上拉加载更多
        mPullToFlashView.setOnScrollListener(new AbsListView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
                if (scrollState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE) {
                    if (mPullToFlashView.getLastVisiblePosition() == (mPullToFlashView
                            .getCount() - 1)) {
                        load_more_tv.setText("正在加载最新数据....");
                          //进行获取最新数据
                        new Thread(new Runnable() {
                            @Override
                            public void run() {
                                try {
                                    Thread.sleep(5000);
                                    newHandler.sendEmptyMessage(2);
                                } catch (InterruptedException e) {
                                    e.printStackTrace();
                                }

                            }
                        }).start();
                    }
                }
                if (scrollState == AbsListView.OnScrollListener.SCROLL_STATE_FLING) {
                    //正在滑动中，当前listview正在滑动 可以暂停图片加载器或者其他一些耗时操作
                } else {

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

            }
        });
    }




    private void initTitles(){
        mTitles=new ArrayList<String>();
        for(int i=0;i<20;i++){
            int index=i+1;
            mTitles.add("当前是:"+index+"");
        }
    }

    private void refreshTitles(){
        List<String> newTitles=new ArrayList<String>();
        for(int i=0;i<5;i++){
            int index=i+1;
            newTitles.add("新数据是:"+index+"");
        }
        newTitles.addAll(mTitles);
        mTitles.removeAll(mTitles);
        mTitles.addAll(newTitles);
    }
    private void moreTitles(){
        List<String> newTitles=new ArrayList<String>();
        for(int i=0;i<8;i++){
            int index=i+1;
            newTitles.add("更多数据是:"+index+"");
        }
        mTitles.addAll(newTitles);
    }



    class PullAdapter extends BaseAdapter{

        @Override
        public int getCount() {
            return mTitles.size();
        }

        @Override
        public Object getItem(int position) {
            return mTitles.get(position);
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            Hondler _Hondler=null;
            if(convertView==null){
                _Hondler=new Hondler();
                convertView=mLayoutInflater.inflate(R.layout.lv_main_item,null);
                _Hondler.tv_item=(TextView)convertView.findViewById(R.id.tv_item);
                convertView.setTag(_Hondler);
            }else
            {
                _Hondler=(Hondler)convertView.getTag();
            }
            _Hondler.tv_item.setText(mTitles.get(position));
            return convertView;
        }


    }

    static class Hondler{
        TextView tv_item;
    }

}

底部，上拉加载更多，xml布局如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/load_next_page_layout"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:background="@color/transparent"
    android:gravity="center"
    android:orientation="vertical" >

    <RelativeLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="5dip"
        android:layout_marginTop="5dip"
        android:gravity="center" >

        <ProgressBar
            android:id="@+id/load_next_page_progress"
            android:layout_width="20dip"
            android:layout_height="20dip"
            android:layout_centerVertical="true"

            android:indeterminate="true"
            android:indeterminateDrawable="@drawable/ic_loading_refresh"/>

        <TextView
            android:id="@+id/load_next_page_text"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:layout_centerVertical="true"
            android:layout_marginLeft="4dip"
            android:layout_toRightOf="@id/load_next_page_progress"
            android:clickable="true"
            android:textColor="@color/black"
            android:textSize="16sp" />
    </RelativeLayout>

</LinearLayout>

显示上次加载时间的实现类UIUtils如下：

package com.example.utils;



import java.text.SimpleDateFormat;
import java.util.Calendar;

import android.annotation.SuppressLint;
import android.content.Context;

import com.example.text.PullListviewActivity;
import com.example.text.SharedPreferencesHelper;
import com.example.view.PullToFlashView;
import com.ruiqi.application.FDApplication;

/**
 * 当前类注释:进行PullToRefreshListView 下拉刷新控件的更新时间设置
 * 
 */
public class UIUtils {

    public static  final  String DEMO_PULL_TIME_KEY="demo_pull_time_key";

    /**
     * 设置上次更新数据时间
     * @param listView
     * @param key
     */
    public static void setPullToRefreshLastUpdated(PullToFlashView listView, String key,Context context) {
        SharedPreferencesHelper spHelper = SharedPreferencesHelper.getInstance(context);
        long lastUpdateTimeStamp = spHelper.getLongValue(key);
        listView.setLastUpdated(getUpdateTimeString(lastUpdateTimeStamp));
    }

    /**
     * 保存更新数据时间
     * @param listView
     * @param key
     */
    public static void savePullToRefreshLastUpdateAt(PullToFlashView listView, String key) {
        listView.onRefreshComplete();
        SharedPreferencesHelper spHelper = SharedPreferencesHelper.getInstance(FDApplication.getInstance());
        long lastUpdateTimeStamp=System.currentTimeMillis();
        spHelper.putLongValue(key, lastUpdateTimeStamp);
        listView.setLastUpdated(getUpdateTimeString(lastUpdateTimeStamp));
    }

    /**
     * 更新时间字符串
     * @param timestamp
     * @return
     */
    @SuppressLint("SimpleDateFormat")
    public static String getUpdateTimeString(long timestamp) {
        if (timestamp <= 0) {
            return "上次更新时间:";
        } else {
            String textDate = "上次更新时间:";
            Calendar now = Calendar.getInstance();
            Calendar c = Calendar.getInstance();
            c.setTimeInMillis(timestamp);
            if (c.get(Calendar.YEAR) == now.get(Calendar.YEAR)
                    && c.get(Calendar.MONTH) == now.get(Calendar.MONTH)
                    && c.get(Calendar.DATE) == now.get(Calendar.DATE)) {
                SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
                return textDate += sdf.format(c.getTime());
            } else if (c.get(Calendar.YEAR) == now.get(Calendar.YEAR)) {
                SimpleDateFormat sdf = new SimpleDateFormat("MM/dd HH:mm");
                return textDate += sdf.format(c.getTime());
            } else {
                SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm");
                return textDate += sdf.format(c.getTime());
            }
        }
    }
}

主布局文件如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
      <LinearLayout
        android:id="@+id/linear_bar"
        android:layout_width="fill_parent"
        android:layout_height="1dp"
        android:orientation="vertical"
        android:background="#FF6600"
        android:visibility="gone"
        > 
    </LinearLayout> 
    <RelativeLayout

        android:layout_width="fill_parent"
        android:layout_height="49dp"
        android:background="#FF6600"
        >
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:text="下拉刷新测试"/>
    </RelativeLayout>
    <com.example.view.PullToFlashView
        android:id="@+id/lv_pull_item"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:cacheColorHint="#00000000"/>

</LinearLayout>

好了，上面就是自定义实现下拉刷新和 上拉加载的所有代码了，其实实现逻辑很简单，只是我写的复杂了。就将就着看吧~~~