Android动态刷新listview中的数据

Android动态刷新listview中的数据

　　【IT168技术】之前一直困扰listview刷新后位置的问题，现在才明白，原来不能重新设置listview的adapter，而应该用notifyDataSetChanged()来刷新，这样位置就不会置顶。

　　下面做了一个测试的例子，点击最后一条记录，会增加一条新的记录，

　　代码如下：

　　1.TestAdapter

package com.TestAdapter;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.AbsListView;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;

public  class TestAdapter extends Activity {
     /**  Called when the activity  is  first created.  */
     private   int [] images ;
     private  ListView listview;
     private  MyAdapter adapter;
    List < Map < String , Integer >>  al;
    
    @Override
     public  void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        images  =    new   int []{android.R.drawable.ic_btn_speak_now,
                android.R.drawable.alert_light_frame,
                android.R.drawable.arrow_down_float,
                android.R.drawable.arrow_up_float,
                android.R.drawable.btn_star_big_off,
                android.R.drawable.btn_star_big_on,
                android.R.drawable.button_onoff_indicator_off,
                android.R.drawable.button_onoff_indicator_on,
                android.R.drawable.checkbox_off_background,
                android.R.drawable.checkbox_on_background,
                android.R.drawable.ic_btn_speak_now,
                android.R.drawable.ic_delete};
        listview  =  (ListView)findViewById(R.id.listview);
        al  =   new  ArrayList < Map < String , Integer >> ();
         for ( int  i = 0 ; i < 12 ; i ++ ){
            HashMap < String , Integer   >  map  =   new  HashMap < String , Integer > ();
            map.put( "" + i, images[i]);
            al.add(map);
        }

        adapter  =   new  MyAdapter(this, al, R.layout.list_item,  new   String []{ " imageview " ,  " tv " }, 
                 new   int []{R.id.imageview, R.id.tv});
        listview.setAdapter(adapter);
        listview.setOnItemClickListener( new  OnItemClickListener() {

             public  void onItemClick(AdapterView < ? >  arg0, View arg1,  int  count,
                     long  arg3) {
                 if (adapter.getCount() == count + 1 ){
                    HashMap < String  , Integer >  map  =   new  HashMap < String ,  Integer > ();
                    map.put( "" + (adapter.mItemList.size()), android.R.drawable.ic_dialog_email);
                    al.add(map);
                    adapter.mItemList  =  al;
                    adapter.notifyDataSetChanged();
                    Toast.makeText(TestAdapter.this,  " 正在刷新 " , Toast.LENGTH_SHORT).show();
                }                
            }
        });
        
    }
    
    
     private  class MyAdapter extends SimpleAdapter{
         int  count  =   0 ;
         private  List < Map < String ,  Integer >>  mItemList;
         public  MyAdapter(Context context, List < ? extends Map < String ,  Integer >>  data,
                 int  resource,  String [] from,  int []  to ) {
            super(context, data, resource, from,  to );
            mItemList  =  (List < Map < String ,  Integer >> ) data;
             if (data  ==   null ){
                count  =   0 ;
            } else {
                count  =  data.size();
            }
        }
         public   int  getCount() {
            return mItemList.size();
        }

         public   Object  getItem( int  pos) {
            return pos;
        }

         public   long  getItemId( int  pos) {
            return pos;
        }
        
        @Override
         public  View getView( int  position, View convertView, ViewGroup parent) {
            Map < String  , Integer >  map  =  mItemList.get(position);
             int  image   =   map.get( "" + position);
            View view  =  super.getView(position, convertView, parent);
            ImageView imageview  =  (ImageView)view.findViewById(R.id.imageview);
            TextView tv  =  (TextView)view.findViewById(R.id.tv);
            imageview.setBackgroundResource(image);
            tv.setText( "" + position);
            return view;
        }
    }
}

　　2.main.xml

< ?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/listview "
        android:layout_width = " fill_parent "
        android:layout_height = " wrap_content "
     > ListView >
    
LinearLayout >

　　3.list_item.xml

< ?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 "
     >
     < ImageView 
    android:id = " @+id/imageview "
    android:layout_width = " wrap_content "
    android:layout_height = " wrap_content " >
     ImageView >
     < TextView
        android:id = " @+id/tv "  android:layout_width = " fill_parent "
        android:layout_height = " wrap_content "
     > TextView >
LinearLayout >