Android上拉刷新列表数据

   android开发中，listview是最常用的控件之一，通常我们可以再微博、微信等很多应用里面都可以看到下拉刷新，以及上拉刷新，点击查看更多等功能。这里介绍下说下上拉刷新。
  上拉刷新其实和底部的“点击加载更多”的功能差不多。都是分页加载数据的一个实现。具体是去监听滚动条事件，下拉到底部时进行操作。

package com.xzw.demo;      import java.util.ArrayList;  import java.util.HashMap;  import java.util.List;      import android.os.Bundle;  import android.os.Handler;  import android.app.Activity;  import android.util.Log;  import android.view.Menu;  import android.view.View;  import android.widget.AbsListView;  import android.widget.AbsListView.OnScrollListener;  import android.widget.ListView;  import android.widget.SimpleAdapter;  import android.widget.Toast;      public class MainActivity extends Activity implements OnScrollListener {                    private static final String TAG = "MainActivity";                    private ListView listView;          private View moreView; //加载更多页面                    private SimpleAdapter adapter;          private ArrayList<HashMap<String, String>> listData;                    private int lastItem;      private int count;             @Override      public void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.activity_main);                    listView = (ListView)findViewById(R.id.listView);          moreView = getLayoutInflater().inflate(R.layout.load, null);          listData = new ArrayList<HashMap<String,String>>();                    prepareData(); //准备数据          count = listData.size();                 adapter = new SimpleAdapter(this, listData,R.layout.item,                           new String[]{"itemText"}, new int[]{R.id.itemText});                    listView.addFooterView(moreView); //添加底部view，一定要在setAdapter之前添加，否则会报错。                    listView.setAdapter(adapter); //设置adapter          listView.setOnScrollListener(this); //设置listview的滚动事件      }          private void prepareData(){  //准备数据              for(int i=0;i<10;i++){                      HashMap<String, String> map = new HashMap<String, String>();                      map.put("itemText", "测试数据"+i);                      listData.add(map);              }                    }            private void loadMoreData(){ //加载更多数据               count = adapter.getCount();               for(int i=count;i<count+5;i++){                      HashMap<String, String> map = new HashMap<String, String>();                      map.put("itemText", "测试数据"+i);                      listData.add(map);              }              count = listData.size();      }              @Override          public void onScroll(AbsListView view, int firstVisibleItem,                          int visibleItemCount, int totalItemCount) {                                    Log.i(TAG, "firstVisibleItem="+firstVisibleItem+"\nvisibleItemCount="+                                  visibleItemCount+"\ntotalItemCount"+totalItemCount);                                    lastItem = firstVisibleItem + visibleItemCount - 1;  //减1是因为上面加了个addFooterView                            }              @Override          public void onScrollStateChanged(AbsListView view, int scrollState) {                   Log.i(TAG, "scrollState="+scrollState);                  //下拉到空闲是，且最后一个item的数等于数据的总数时，进行更新                  if(lastItem == count  && scrollState == this.SCROLL_STATE_IDLE){                           Log.i(TAG, "拉到最底部");                          moreView.setVisibility(view.VISIBLE);                                         mHandler.sendEmptyMessage(0);                                             }                            }          //声明Handler          private Handler mHandler = new Handler(){                  public void handleMessage(android.os.Message msg) {                          switch (msg.what) {                          case 0:                                                                 try {                                          Thread.sleep(3000);                                  } catch (InterruptedException e) {                                          // TODO Auto-generated catch block                                          e.printStackTrace();                                  }                              loadMoreData();  //加载更多数据，这里可以使用异步加载                              adapter.notifyDataSetChanged();                              moreView.setVisibility(View.GONE);                                                             if(count > 30){                                      Toast.makeText(MainActivity.this, "木有更多数据！", 3000).show();                                    listView.removeFooterView(moreView); //移除底部视图                              }                                  Log.i(TAG, "加载更多数据");                                  break;              case 1:                                                                    break;                          default:                                  break;                          }                  };          };        }