不是異步的例子，顯然有個延遲。

    
package com.ql.app;

import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class ProcessorBarTest extends Activity {
	private ListView listview;
	private Context mContext;
	private List<String> mAppList;
	private ArrayAdapter mAdapter;
	private boolean mIsLoaded = false;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.screen_1);
		
		listview = (ListView)findViewById(R.id.listview);
		mContext = this;
		mAppList = new ArrayList<String>();
		mAdapter = new ArrayAdapter(mContext,android.R.layout.simple_list_item_1, mAppList);
		listview.setAdapter(mAdapter);
		
		// 獲取已經安裝程序列表
		PackageManager pm = mContext.getPackageManager();

                //有入口&圖標的一定就是應用
		Intent intent = new Intent(Intent.ACTION_MAIN, null);//入口就是應用
		intent.addCategory(Intent.CATEGORY_LAUNCHER);//有圖標的就是應用？
		List<ResolveInfo> list = pm.queryIntentActivities(intent, 0);
		
		for (int i=0; i<list.size(); i++) {
			mAppList.add(list.get(i).loadLabel(pm).toString());
		}
		mAdapter.notifyDataSetChanged();
	}
	
}

  

AsyncTask是抽象類.AsyncTask定義了三種泛型類型 Params，Progress和Result。
◆Params 啟動任務執行的輸入參數，比如HTTP請求的URL。
◆Progress 后臺任務執行的百分比。
◆Result 后臺執行任務最終返回的結果，比如String。
AsyncTask的執行分為四個步驟，每一步都對應一個回調方法，這些方法不應該由應用程序調用，開發者需要做的就是實現這些方法。
onPreExecute(), 該方法將在執行實際的后臺操作前被UI thread調用?？梢栽谠摲椒ㄖ凶鲆恍蕚涔ぷ?，如在界面上顯示一個進度條。
doInBackground(Params...), 將在onPreExecute 方法執行后馬上執行，該方法運行在后臺線程中。這里將主要負責執行那些很耗時的后臺計算工作。可以調用 publishProgress方法來更新實時的任務進度。該方法是抽象方法，子類必須實現。
onProgressUpdate(Progress...),在publishProgress方法被調用后，UI thread將調用這個方法從而在界面上展示任務的進展情況，例如通過一個進度條進行展示。
onPostExecute(Result), 在doInBackground 執行完成后，onPostExecute 方法將被UI thread調用，后臺的計算結果將通過該方法傳遞到UI thread.
為了正確的使用AsyncTask類，以下是幾條必須遵守的準則：
1) Task的實例必須在UI thread中創建
2) execute方法必須在UI thread中調用
3) 不要手動的調用onPreExecute(), onPostExecute(Result)，doInBackground(Params...), onProgressUpdate(Progress...)這幾個方法
4) 該task只能被執行一次，否則多次調用時將會出現異常

下面是AsyncTask異步獲取已安裝程序列表的例子：

    
public class Screen1 extends Activity{
	private static final String tag="Screen1";
	private ListView listview;
	private Context mContext;
	private List<ResolveInfo> list;
	private AppAdapter adapter;
	private PackageManager pm;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		//給Activity注冊界面進度條功能
		requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
		setContentView(R.layout.screen_1);
		mContext = this;
		
		list=new ArrayList<ResolveInfo>();
		pm = mContext.getPackageManager();
		listview = (ListView)findViewById(R.id.listview);
		
		adapter = new AppAdapter(mContext);
		
		listview.setAdapter(adapter);
		listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {

			@Override
			public void onItemClick(AdapterView<?> parent, View view,
					int position, long id) {
				// TODO Auto-generated method stub
				Log.i(tag, "---------------onItemClick-----------------");
				ResolveInfo info=list.get(position);
				String packageName = info.activityInfo.packageName;
				String className = info.activityInfo.name;

				Intent intent = new Intent();
				intent.setClassName(packageName, className);
				startActivity(intent);
			}
		});
		new MyTask().execute();
		
	}


	class AppAdapter extends BaseAdapter{
		Context context;
		AppAdapter(Context context){
			this.context=context;
		}
		@Override
		public int getCount() {
			// TODO Auto-generated method stub
			return list.size();
		}

		@Override
		public Object getItem(int position) {
			// TODO Auto-generated method stub
			return list.get(position);
		}

		@Override
		public long getItemId(int position) {
			// TODO Auto-generated method stub
			return position;
		}

		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			// TODO Auto-generated method stub
			if(convertView==null){
				LayoutInflater inflater=getLayoutInflater().from(context);
				convertView=inflater.inflate(R.layout.simple_item_2, null);
			}
			ImageView iv=(ImageView)convertView.findViewById(R.id.icon);
			TextView tv=(TextView)convertView.findViewById(R.id.text);
			
			ResolveInfo info=list.get(position);
			iv.setBackgroundDrawable(info.activityInfo.loadIcon(pm));
			tv.setText(info.activityInfo.loadLabel(pm));
			return convertView;
		}
		
	}
	
	class MyTask extends AsyncTask<String, Integer, String>{

		@Override
		protected void onPreExecute() {
			setProgressBarIndeterminateVisibility(true);
			showProgress();
		}

		@Override
		protected void onPostExecute(String param) {
			setProgressBarIndeterminateVisibility(false);
			adapter.notifyDataSetChanged();
			closeProgress();
		}

		@Override
		protected void onCancelled() {
			// TODO Auto-generated method stub
			super.onCancelled();
		}

		@Override
		protected void onProgressUpdate(Integer... values) {
			// TODO Auto-generated method stub
			super.onProgressUpdate(values);
		}

		@Override
		protected String doInBackground(String... params) {
			// TODO Auto-generated method stub
			// 獲取已經安裝程序列表
			Intent intent = new Intent(Intent.ACTION_MAIN, null);
			intent.addCategory(Intent.CATEGORY_LAUNCHER);
			list = pm.queryIntentActivities(intent, 0);
	        Collections.sort(list, new ResolveInfo.DisplayNameComparator(pm));
			return null;
		}
		
	}
	
	private Dialog 		dialog;
    protected void showProgress() {
		if(dialog == null) {
			dialog =  new Dialog(this, R.style.Theme_TransparentDialog);
//			dialog.setContentView(R.layout.progress_dialog);
			dialog.setContentView(new ProgressBar(this));
			dialog.setCancelable(true);
			dialog.show();
		}
	}
    //
    protected void closeProgress() {
		
		if(dialog != null) {
			dialog.cancel();
			dialog = null;
		}
	}
    public boolean isShowing(){
    	if(dialog != null) {
    		return dialog.isShowing();
    	}
    	return false;
    }
    
}

  

simple_item_2.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"
    >
    <TextView  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="應用列表"
    />
    <ListView  android:id="@+id/listview"
    	android:layout_width="fill_parent" 
    	android:layout_height="fill_parent" 
    />
</LinearLayout>

  

Android得到系統已安裝應用程序包列表方法 自定義ListView顯示 PackageManager的使用

AyncTask 實戰 模擬GridView 動態更新效果
http://www.ophonesdn.com/article/show/80

異步獲取已安裝程序列表（PackageManager+AsyncTask）