andriod PullToRefresh的使用 构建下拉刷新的listView

下载源码后（https://github.com/chrisbanes/Android-PullToRefresh），里面有个Library工程，添加工程到Eclipse中；

1.导入Library 

2.布局xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:orientation="vertical" ><!--     The PullToRefreshListView replaces a standard ListView widget. -->    <com.handmark.pulltorefresh.library.PullToRefreshListView        xmlns:ptr="http://schemas.android.com/apk/res-auto"        android:id="@+id/pull_refresh_list"        android:layout_width="fill_parent"        android:layout_height="fill_parent"        android:cacheColorHint="#00000000"        android:divider="#19000000"        android:dividerHeight="4dp"        android:fadingEdge="none"        android:fastScrollEnabled="false"        android:footerDividersEnabled="false"        android:headerDividersEnabled="false"        android:smoothScrollbar="true"        ptr:ptrMode="both" //上下都能刷新         /></LinearLayout>

3.java代码

package com.example.pulltoflush;import java.util.ArrayList;import java.util.List;import java.util.Set;import java.util.TreeSet;import com.handmark.pulltorefresh.library.PullToRefreshBase;import com.handmark.pulltorefresh.library.PullToRefreshBase.OnRefreshListener;import com.handmark.pulltorefresh.library.PullToRefreshListView;import android.os.AsyncTask;import android.os.Bundle; import android.app.Activity; import android.widget.ArrayAdapter;import android.widget.ListView;public class MainActivity extends Activity {    private PullToRefreshListView mPullRefreshListView;        private ArrayAdapter<String> mArrayAdpter;    private List<String> mArraylist=new ArrayList<String>();     protected void onCreate(Bundle savedInstanceState) {            super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);                mPullRefreshListView = (PullToRefreshListView) findViewById(R.id.pull_refresh_list);                mArrayAdpter=new ArrayAdapter<String>(this,android.R.layout.simple_expandable_list_item_1,mArraylist);        mPullRefreshListView.setAdapter(mArrayAdpter);      mPullRefreshListView.setOnRefreshListener(new OnRefreshListener<ListView>() {@Overridepublic void onRefresh(PullToRefreshBase<ListView> refreshView) {new GetDataTask().execute();} });    } private class GetDataTask extends AsyncTask<Void, Void, String> {protected String doInBackground(Void... arg0){try {Thread.sleep(2000);} catch (InterruptedException e) {} return shuangsheqiu();} protected void onPostExecute(String result) {mArraylist.add(result);mArrayAdpter.notifyDataSetChanged();mPullRefreshListView.onRefreshComplete();super.onPostExecute(result); }} private String shuangsheqiu(){// TODO Auto-generated method stubSet<String> treeSet=new TreeSet<String>();do{treeSet.add(getredball()); } while (treeSet.size()!=6);String[] arrayString=new String[6];arrayString=treeSet.toArray(arrayString);StringBuilder resb=new StringBuilder();resb.append("[第"+(mArraylist.size()+1)+"组] ");for(int i=0;i<6;i++){resb.append(arrayString[i]);resb.append("-");}resb.append("+蓝:");resb.append(getbulball());  return resb.toString();}private String getredball(){ int i= (int)(Math.random()*33+1); if(i<10){ return "0"+String.valueOf(i); }else{ return String.valueOf(i); }}private String getbulball(){ int i= (int)(Math.random()*16+1); if(i<10){ return "0"+String.valueOf(i); }else{ return String.valueOf(i); }}    }

（1）派生自AsyncTask

由于派生自AsyncTask，所以下面的那个函数doInBackground和onPostExecute就不难理解了，这两个函数是AsyncTask必须是重写的两个函数
（2）doInBackground函数

doInBackground执行要于后台执行的语句，返回的值可以是任意类型，但要提前在extends AsyncTask<Void, Void, String> 中定义，这个返回值会做为onPostExecute的参数result传到onPostExecute函数中；如果对于网络访问程序，doInBackground就执行访问网络的代码，然后讲返回值存在result中传给onPostExecute函数，以刷新列表；

 （3）onPostExecute函数

 onPostExecute（）是对返回的值进行操作，并添加到ListView的列表中，有两种添加方式添加到头部----mArraylist.addFirst(result);和添加在尾部----

mArraylist<span style="font-family: Arial; background-color: rgb(255, 255, 255);">.addLast(result);</span>