Android中ListView如何分页加载数据

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
  android:orientation="vertical" 
  android:layout_width="fill_parent" 
  android:layout_height="fill_parent" 
  android:paddingLeft="3dp" 
  android:paddingRight="3dp"> 
  <ListView 
    android:id="@id/android:list" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"/> 
</LinearLayout> 

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
  android:orientation="vertical" 
  android:layout_width="fill_parent" 
  android:layout_height="fill_parent"> 
  <TextView 
    android:id="@+id/list_item_text" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:gravity="center" 
    android:textSize="20sp" 
    android:paddingTop="10dp" 
    android:paddingBottom="10dp"/> 
</LinearLayout> 

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout 
 xmlns:android="http://schemas.android.com/apk/res/android" 
 android:orientation="vertical" 
 android:layout_width="fill_parent" 
 android:layout_height="wrap_content"> 
 <Button 
    android:id="@+id/loadMoreButton" 
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="load more" 
    android:onClick="loadMore"/> 
</LinearLayout> 

package com.scott.loadmore; 
 
import java.util.List; 
 
import android.content.Context; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.BaseAdapter; 
import android.widget.TextView; 
 
public class ListViewAdapter extends BaseAdapter { 
  private List<String> items; 
  private LayoutInflater inflater; 
   
  public ListViewAdapter(Context context, List<String> items) { 
    this.items = items; 
    inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);    
  } 
   
  @Override 
  public int getCount() { 
    return items.size(); 
  } 
 
  @Override 
  public Object getItem(int position) { 
    return items.get(position); 
  } 
 
  @Override 
  public long getItemId(int position) { 
    return position; 
  } 
 
  @Override 
  public View getView(int position, View view, ViewGroup parent) { 
    if (view == null) { 
      view = inflater.inflate(R.layout.list_item, null); 
    } 
    TextView text = (TextView) view.findViewById(R.id.list_item_text); 
    text.setText(items.get(position)); 
    return view; 
  } 
   
  /** 
   * 添加列表项 
   * @param item 
   */ 
  public void addItem(String item) { 
    items.add(item); 
  } 
} 

package com.scott.loadmore; 
 
import java.util.ArrayList; 
 
import android.app.ListActivity; 
import android.os.Bundle; 
import android.os.Handler; 
import android.util.Log; 
import android.view.View; 
import android.widget.AbsListView; 
import android.widget.AbsListView.OnScrollListener; 
import android.widget.Button; 
import android.widget.ListView; 
 
public class MainActivity extends ListActivity implements OnScrollListener { 
  private ListView listView; 
  private int visibleLastIndex = 0;  //最后的可视项索引 
  private int visibleItemCount;    // 当前窗口可见项总数 
  private ListViewAdapter adapter; 
  private View loadMoreView; 
  private Button loadMoreButton; 
  private Handler handler = new Handler(); 
 
  @Override 
  public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 
     
    loadMoreView = getLayoutInflater().inflate(R.layout.load_more, null); 
    loadMoreButton = (Button) loadMoreView.findViewById(R.id.loadMoreButton); 
 
    listView = getListView();        //获取id是list的ListView 
     
    listView.addFooterView(loadMoreView);  //设置列表底部视图 
 
    initAdapter(); 
     
    setListAdapter(adapter);        //自动为id是list的ListView设置适配器 
     
    listView.setOnScrollListener(this);   //添加滑动监听 
  } 
   
  /** 
   * 初始化适配器 
   */ 
  private void initAdapter() { 
    ArrayList<String> items = new ArrayList<String>(); 
    for (int i = 0; i < 10; i++) { 
      items.add(String.valueOf(i + 1)); 
    } 
    adapter = new ListViewAdapter(this, items); 
  } 
 
  /** 
   * 滑动时被调用 
   */ 
  @Override 
  public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { 
    this.visibleItemCount = visibleItemCount; 
    visibleLastIndex = firstVisibleItem + visibleItemCount - 1; 
  } 
 
  /** 
   * 滑动状态改变时被调用 
   */ 
  @Override 
  public void onScrollStateChanged(AbsListView view, int scrollState) { 
    int itemsLastIndex = adapter.getCount() - 1;  //数据集最后一项的索引 
    int lastIndex = itemsLastIndex + 1;       //加上底部的loadMoreView项 
    if (scrollState == OnScrollListener.SCROLL_STATE_IDLE && visibleLastIndex == lastIndex) { 
      //如果是自动加载,可以在这里放置异步加载数据的代码 
      Log.i("LOADMORE", "loading..."); 
    } 
  } 
   
  /** 
   * 点击按钮事件 
   * @param view 
   */ 
  public void loadMore(View view) { 
    loadMoreButton.setText("loading...");  //设置按钮文字loading 
    handler.postDelayed(new Runnable() { 
      @Override 
      public void run() { 
         
        loadData(); 
         
        adapter.notifyDataSetChanged(); //数据集变化后,通知adapter 
        listView.setSelection(visibleLastIndex - visibleItemCount + 1); //设置选中项 
         
        loadMoreButton.setText("load more");  //恢复按钮文字 
      } 
    }, 2000); 
  } 
   
  /** 
   * 模拟加载数据 
   */ 
  private void loadData() { 
    int count = adapter.getCount(); 
    for (int i = count; i < count + 10; i++) { 
      adapter.addItem(String.valueOf(i + 1)); 
    } 
  } 
}