异步获取已安装程序列表（PackageManager+AsyncTask）

文章出处：http://gundumw100.iteye.com/blog/1067414

 

AsyncTask是抽象类.AsyncTask定义了三种泛型类型 Params，Progress和Result。 
◆Params 启动任务执行的输入参数，比如HTTP请求的URL。 
◆Progress 后台任务执行的百分比。 
◆Result 后台执行任务最终返回的结果，比如String。 
AsyncTask的执行分为四个步骤，每一步都对应一个回调方法，这些方法不应该由应用程序调用，开发者需要做的就是实现这些方法。 
onPreExecute(), 该方法将在执行实际的后台操作前被UI thread调用。可以在该方法中做一些准备工作，如在界面上显示一个进度条。 
doInBackground(Params...), 将在onPreExecute 方法执行后马上执行，该方法运行在后台线程中。这里将主要负责执行那些很耗时的后台计算工作。可以调用 publishProgress方法来更新实时的任务进度。该方法是抽象方法，子类必须实现。 
onProgressUpdate(Progress...),在publishProgress方法被调用后，UI thread将调用这个方法从而在界面上展示任务的进展情况，例如通过一个进度条进行展示。 
onPostExecute(Result), 在doInBackground 执行完成后，onPostExecute 方法将被UI thread调用，后台的计算结果将通过该方法传递到UI thread. 
为了正确的使用AsyncTask类，以下是几条必须遵守的准则： 
1) Task的实例必须在UI thread中创建 
2) execute方法必须在UI thread中调用 
3) 不要手动的调用onPreExecute(), onPostExecute(Result)，doInBackground(Params...), onProgressUpdate(Progress...)这几个方法 
4) 该task只能被执行一次，否则多次调用时将会出现异常 

下面是AsyncTask异步获取已安装程序列表的例子： 

 

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);  
        //给Activity注册界面进度条功能  
        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  
            // 获取已经安装程序列表  
            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="应用列表"  
    />  
    <ListView  android:id="@+id/listview"  
        android:layout_width="fill_parent"   
        android:layout_height="fill_parent"   
    />  
</LinearLayout>  

 

 

Android得到系统已安装应用程序包列表方法 自定义ListView显示 PackageManager的使用 

AyncTask 实战 模拟GridView 动态更新效果 
http://www.ophonesdn.com/article/show/80