Android实现简单的分批加载ListView

内容摘要
每次滑动至底端，从数据库中获取10条数据，并加载于ListView中
数据库




package com.example.listviewbatchloading;

import android.content.Context;
import android.d
文章正文

每次滑动至底端，从数据库中获取10条数据，并加载于ListView中

数据库

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package com.example.listviewbatchloading;
  
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
  
public class PersonDb extends SQLiteOpenHelper {
  
  public PersonDb(Context context) {
    super(context, "creature", null, 1);
    // TODO Auto-generated constructor stub
  }
  
  @Override
  public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub
    db.execSQL("create table people(_id integer primary key autoincrement,name char,number char)");
  }
  
  @Override
  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub
    db.execSQL("drop table people");
    onCreate(db);
  }
  
}

数据库的业务封装，其中获取更多数据的是核心代码

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package com.example.listviewbatchloading;
  
/**
 * 数据库的业务封装类
 */
  
import java.util.ArrayList;
import java.util.List;
  
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
  
public class PersonList {
    
  PersonDb personDb;
    
  public PersonList(Context context){
    this.personDb = new PersonDb(context);
  }
    
  /**
   *   获取一定条目的数据
   * @param startIndex
   *   开始取数据的位置
   * @param num
   *   取多少条数据
   */
  public List<Person> getMoreDatas(int startIndex,int num){
      
    List<Person> list = new ArrayList<Person>();
    SQLiteDatabase db = personDb.getWritableDatabase();
    Cursor cursor = db.rawQuery("select name,number from people order by _id desc limit ?,?",
        new String[]{startIndex + "",num + ""});
      
    while(cursor.moveToNext()){
      Person person = new Person();
      person.setName(cursor.getString(cursor.getColumnIndex("name")));
      person.setNumber(cursor.getString(cursor.getColumnIndex("number")));
      list.add(person);
    }
      
    cursor.close();
    db.close();
      
      
    return list;
      
  }
    
  /**
   *   添加数据库条目
   * @param name
   * @param number
   */
  public void add(String name,String number){
      
    SQLiteDatabase db = personDb.getWritableDatabase();
      
    ContentValues cv = new ContentValues();
    cv.put("name", name);
    cv.put("number", number);
      
    db.insert("people", null, cv);
    db.close();
  }
    
}

功能实现

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package com.example.listviewbatchloading;
  
import java.util.ArrayList;
import java.util.List;
  
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
  
public class MainActivity extends Activity {
    
  private ListView lv ;
  private List<Person> datas = new ArrayList<Person>();
  private static int PERPAGE = 10; //每页加载数目
  private static final int FINISH = 0;//数据加载完成
  private List<Person> moreDatas;//每次加载的数据
  private MyAdapter adapter;
  private PersonList personList ;
    
  //若数据较多，耗时较长，数据加载完成时，发送FINISH至handler，并通知ListView更新数据
  private Handler handler = new Handler(){
    public void handleMessage(android.os.Message msg) {
        
      switch (msg.what) {
      case FINISH:
        if (moreDatas.size() != 0) {
          System.out.println(moreDatas.toString());
          adapter.notifyDataSetChanged();
        }else {
          Toast.makeText(MainActivity.this, "没有更多数据", Toast.LENGTH_SHORT).show();
        }
        break;
  
      default:
        break;
      }
        
        
    };
  };
    
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    initView();
    initData();
    initEvent();
  }
  /**
   *   为ListView添加滚动监听事件，但滚动至最后一行时，加载更多数据
   */
  private void initEvent() {
    lv.setOnScrollListener(new OnScrollListener() {
        
      @Override
      public void onScrollStateChanged(AbsListView view, int scrollState) {
        // TODO Auto-generated method stub
        if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) {
          int lastVisiblePosition = lv.getLastVisiblePosition();
          if (lastVisiblePosition == datas.size() - 1) {
            initData();
            System.out.println("加载更多数据");
          }
        }
      }
        
      @Override
      public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
        // TODO Auto-generated method stub
          
      }
    });
  }
  
  private void initView() {
      
    setContentView(R.layout.activity_main);
      
    lv = (ListView) findViewById(R.id.lv);
    personList = new PersonList(getApplicationContext());
    adapter = new MyAdapter();
    lv.setAdapter(adapter);
  }
    
  /**
   * 在子线程中加载数据，避免主线程阻塞
   */
  private void initData() {
    new Thread() {
  
      public void run() {
  
        // 加载更多数据
        moreDatas = personList.getMoreDatas(datas.size(), PERPAGE);
  
        datas.addAll(moreDatas);// 把一个容器的所有数据加进来
        // 取数据完成，发消息通知取数据完成
        handler.obtainMessage(FINISH).sendToTarget();
  
      };
    }.start();
  }
    
  private class ItemView{
    private TextView tv_name;
    private TextView tv_num;
  }
    
  /**
   *   ListView的适配器
   * @author lian
   *
   */
  private class MyAdapter extends BaseAdapter{
  
    @Override
    public int getCount() {
      // TODO Auto-generated method stub
      return datas.size();
    }
  
    @Override
    public Object getItem(int position) {
      // TODO Auto-generated method stub
      return null;
    }
  
    @Override
    public long getItemId(int position) {
      // TODO Auto-generated method stub
      return 0;
    }
  
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        
      ItemView itemView = null;
      if (convertView == null) {
        itemView = new ItemView();
        convertView = View.inflate(getApplicationContext(), R.layout.item_lv, null);
        itemView.tv_name = (TextView) convertView.findViewById(R.id.tv_name);
        itemView.tv_num = (TextView) convertView.findViewById(R.id.tv_num);
        convertView.setTag(itemView);
      }else {
        itemView = (ItemView) convertView.getTag();
      }
        
      Person person = datas.get(position);
      itemView.tv_name.setText(person.getName());
      itemView.tv_num.setText(person.getNumber());
        
      return convertView;
    }
      
  }
    
}

其他Person的JavaBean，以及布局文件，不在赘述

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