Detailed explanation of Android notifyDataSetChanged of dynamic update ListView case

Sometimes we need to modify the generated list and add or modify data. notifyDataSetChanged () can notify Activity to update ListView without refreshing Activity again after modifying the array bound by the adapter. Today's example is to dynamically update ListView through Handler AsyncTask.

<?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"," No. 1 1 Items ");// Put the first 1 The content of item should be changed to " No. 1 1 Items "
         Handler handler=new Handler();
         handler.postDelayed(add,3000);// Delay 3 Second execution 
     }
     Runnable add=new Runnable(){
  
        @Override
        public void run() {
             // TODO Auto-generated method stub
             arr.add(" Increase 1 Items ");// Increase 1 Items 
             Adapter.notifyDataSetChanged();    
         }       
     };
     class editItem extends AsyncTask<String,Integer,String>{
         @Override
         protected String doInBackground(String... params) {
                 arr.set(Integer.parseInt(params[0]),params[1]);
                //params What I get is 1 An array of, params[0] Here it is "0",params[1] Yes " No. 1 1 Items "
                 //Adapter.notifyDataSetChanged();
                 // You cannot call after adding  Adapter.notifyDataSetChanged() Update UI , because with UI Not on the same thread 
                 // Below onPostExecute Method will be used in the doBackground After execution by UI Thread invocation 
             return null;    
         }
  
         @Override
         protected void onPostExecute(String result) {
             // TODO Auto-generated method stub
             super.onPostExecute(result);
             Adapter.notifyDataSetChanged();
             // Complete execution, update UI
         }
  
     }
     private OnItemClickListener lvLis=new OnItemClickListener(){
         @Override
         public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                 long arg3) {
            // Triggered when an entry is clicked 
             //arg2 That is, the position of the item in the point 
            setTitle(String.valueOf(arr.get(arg2)));
  
         }
  
     };
  
 }