[转]notifyDataSetChanged() 动态更新ListView
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.
布局main.xml:
1 <?xml version="1.0" encoding="utf-8"?> 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 3 android:orientation="vertical" 4 android:layout_width="fill_parent" 5 android:layout_height="fill_parent" 6 > 7 <ListView android:id="@+id/lv" 8 android:layout_width="fill_parent" 9 android:layout_height="wrap_content" 10 android:text="@string/hello" 11 /> 12 </LinearLayout>
ListView列表布局playlist.xml:
1 <?xml version="1.0" encoding="utf-8"?> 2 <TextView 3 android:id="@+id/text1" 4 xmlns:android="http://schemas.android.com/apk/res/android" 5 android:layout_width="fill_parent" 6 android:layout_height="30px" 7 android:textSize="18sp" 8 ></TextView>
程序代码：
1 import java.util.ArrayList; 2 3 import android.app.Activity; 4 import android.os.AsyncTask; 5 import android.os.Bundle; 6 import android.os.Handler; 7 import android.view.View; 8 import android.widget.AdapterView; 9 import android.widget.ArrayAdapter; 10 import android.widget.ListView; 11 import android.widget.AdapterView.OnItemClickListener; 12 13 public class main extends Activity { 14 /** Called when the activity is first created. */ 15 ListView lv; 16 ArrayAdapter<String> Adapter; 17 ArrayList<String> arr=new ArrayList<String>(); 18 @Override 19 public void onCreate(Bundle savedInstanceState) { 20 super.onCreate(savedInstanceState); 21 setContentView(R.layout.main); 22 lv=(ListView)findViewById(R.id.lv); 23 arr.add("123"); 24 arr.add("234"); 25 arr.add("345"); 26 Adapter = new ArrayAdapter<String>(this,R.layout.playlist, arr); 27 lv.setAdapter(Adapter); 28 lv.setOnItemClickListener(lvLis); 29 editItem edit= new editItem(); 30 edit.execute("0","第1项");//把第一项内容改为"第一项" 31 Handler handler=new Handler(); 32 handler.postDelayed(add,3000);//延迟3秒执行 33 } 34 Runnable add=new Runnable(){ 35 36 @Override 37 public void run() { 38 // TODO Auto-generated method stub 39 arr.add("增加一项");//增加一项 40 Adapter.notifyDataSetChanged(); 41 } 42 }; 43 class editItem extends AsyncTask<String,Integer,String>{ 44 @Override 45 protected String doInBackground(String... params) { 46 arr.set(Integer.parseInt(params[0]),params[1]); 47 //params得到的是一个数组，params[0]在这里是"0",params[1]是"第1项" 48 //Adapter.notifyDataSetChanged(); 49 //执行添加后不能调用 Adapter.notifyDataSetChanged()更新UI，因为与UI不是同线程 50 //下面的onPostExecute方法会在doBackground执行后由UI线程调用 51 return null; 52 } 53 54 @Override 55 protected void onPostExecute(String result) { 56 // TODO Auto-generated method stub 57 super.onPostExecute(result); 58 Adapter.notifyDataSetChanged(); 59 //执行完毕，更新UI 60 } 61 62 } 63 private OnItemClickListener lvLis=new OnItemClickListener(){ 64 @Override 65 public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, 66 long arg3) { 67 //点击条目时触发 68 //arg2即为点中项的位置 69 setTitle(String.valueOf(arr.get(arg2))); 70 71 } 72 73 }; 74 75 }
