博客

有时候我们需要修改已经生成的列表，添加或者修改数据，notifyDataSetChanged()可以在修改适配器绑定的数组后，不用重新刷新Activity，通知Activity更新ListView。今天的例子就是通过Handler AsyncTask两种方式来动态更新ListView。

<?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"
>
<ListView  android:id="@+id/lv"
android:layout_width="fill_parent" 
android:layout_height="wrap_content" 
android:text="@string/hello"
/>
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<TextView 
android:id="@+id/text1"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="30px"
android:textSize="18sp"
></TextView>

import java.util.ArrayList;  
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.AdapterView.OnItemClickListener;
  
 public class main extends Activity {
     /** Called when the activity is first created. */
     ListView lv;
     ArrayAdapter<String> Adapter;
     ArrayList<String> arr=new ArrayList<String>();
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.main);
         lv=(ListView)findViewById(R.id.lv);
         arr.add("123");
         arr.add("234");
         arr.add("345");
         Adapter = new ArrayAdapter<String>(this,R.layout.playlist, arr);
         lv.setAdapter(Adapter);
         lv.setOnItemClickListener(lvLis); 
         editItem edit= new editItem();
         edit.execute("0","第1项");//把第一项内容改为"第一项"
         Handler handler=new Handler();
         handler.postDelayed(add,3000);//延迟3秒执行
     }
     Runnable add=new Runnable(){
  
        @Override
        public void run() {
             // TODO Auto-generated method stub
             arr.add("增加一项");//增加一项
             Adapter.notifyDataSetChanged();    
         }       
     };
     class editItem extends AsyncTask<String,Integer,String>{
         @Override
         protected String doInBackground(String... params) {
                 arr.set(Integer.parseInt(params[0]),params[1]);
                //params得到的是一个数组，params[0]在这里是"0",params[1]是"第1项"
                 //Adapter.notifyDataSetChanged();
                 //执行添加后不能调用 Adapter.notifyDataSetChanged()更新UI，因为与UI不是同线程
                 //下面的onPostExecute方法会在doBackground执行后由UI线程调用
             return null;    
         }
  
         @Override
         protected void onPostExecute(String result) {
             // TODO Auto-generated method stub
             super.onPostExecute(result);
             Adapter.notifyDataSetChanged();
             //执行完毕，更新UI
         }
  
     }
     private OnItemClickListener lvLis=new OnItemClickListener(){
         @Override
         public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                 long arg3) {
            //点击条目时触发
             //arg2即为点中项的位置
            setTitle(String.valueOf(arr.get(arg2)));
  
         }
  
     };
  
 }