Android的PackageManager類用於檢索目前安裝在裝置上的應用軟體包的資訊。你可以通過呼叫getpackagemanager()得到PackageManager類的一個例項。對查詢和操作安裝包和相關的許可權提供了方法，在下面這個Android的例子中，我們得到了在Android安裝的應用程式列表。

PackageManager packageManager = getPackageManager();
List<ApplicationInfo> list = packageManager.getInstalledApplications(PackageManager.GET_META_DATA)
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packageManager.getInstalledApplications()返回一個列表都是安裝在裝置上的應用程式包。如果我們把 flag GET_UNINSTALLED_PACKAGES設定，一個列表中的所有應用，包括那些設定為dont_delete_data（部分已安裝的應用程式的資料目錄）將返回。

1.建立 佈局檔案

activity_main.xml

你可以看到附件中的截圖，我們將建立一個列表顯示所有已安裝的應用程式。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <ListView
        android:id="@android:id/list"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

</LinearLayout>
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snippet_list_row.xml

這個佈局是由ListView介面卡用於表示應用程式的細節。它顯示應用程式圖示、應用程式名稱和應用程式包。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content" >

    <ImageView
        android:id="@+id/app_icon"
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:padding="3dp"
        android:scaleType="centerCrop" />

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:gravity="center_vertical"
        android:orientation="vertical"
        android:paddingLeft="5dp" >

        <TextView
            android:id="@+id/app_name"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:gravity="center_vertical"
            android:textStyle="bold" />

        <TextView
            android:id="@+id/app_paackage"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:gravity="center_vertical" />
    </LinearLayout>

</LinearLayout>
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2.java 類

AllAppsActivity.java

這是用於初始化和列表已安裝的應用程式的主要應用程式類。從packagemanage得到應用細節列表是一個耗時的任務，我們將在AsyncTask裡面做。同時，類使用自定義介面卡“自定義listview applicationadapter”。

package com.javatechig.listapps;

import java.util.ArrayList;
import java.util.List;
import android.app.AlertDialog;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.ActivityNotFoundException;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.ListView;
import android.widget.Toast;

public class AllAppsActivity extends ListActivity {
	private PackageManager packageManager = null;
	private List<ApplicationInfo> applist = null;
	private ApplicationAdapter listadaptor = null;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		packageManager = getPackageManager();

		new LoadApplications().execute();
	}

	public boolean onCreateOptionsMenu(Menu menu) {
		MenuInflater inflater = getMenuInflater();
		inflater.inflate(R.menu.menu, menu);

		return true;
	}

	public boolean onOptionsItemSelected(MenuItem item) {
		boolean result = true;

		switch (item.getItemId()) {
		case R.id.menu_about: {
			displayAboutDialog();

			break;
		}
		default: {
			result = super.onOptionsItemSelected(item);

			break;
		}
		}

		return result;
	}

	private void displayAboutDialog() {
		final AlertDialog.Builder builder = new AlertDialog.Builder(this);
		builder.setTitle(getString(R.string.about_title));
		builder.setMessage(getString(R.string.about_desc));

		builder.setPositiveButton("Know More", new DialogInterface.OnClickListener() {
		       public void onClick(DialogInterface dialog, int id) {
		    	   Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://stacktips.com"));
		    	   startActivity(browserIntent);
		    	   dialog.cancel();
		       }
		   });
		builder.setNegativeButton("No Thanks!", new DialogInterface.OnClickListener() {
		       public void onClick(DialogInterface dialog, int id) {
		            dialog.cancel();
		       }
		});

		builder.show();
	}

	@Override
	protected void onListItemClick(ListView l, View v, int position, long id) {
		super.onListItemClick(l, v, position, id);

		ApplicationInfo app = applist.get(position);
		try {
			Intent intent = packageManager
					.getLaunchIntentForPackage(app.packageName);

			if (null != intent) {
				startActivity(intent);
			}
		} catch (ActivityNotFoundException e) {
			Toast.makeText(AllAppsActivity.this, e.getMessage(),
					Toast.LENGTH_LONG).show();
		} catch (Exception e) {
			Toast.makeText(AllAppsActivity.this, e.getMessage(),
					Toast.LENGTH_LONG).show();
		}
	}

	private List<ApplicationInfo> checkForLaunchIntent(List<ApplicationInfo> list) {
		ArrayList<ApplicationInfo> applist = new ArrayList<ApplicationInfo>();
		for (ApplicationInfo info : list) {
			try {
				if (null != packageManager.getLaunchIntentForPackage(info.packageName)) {
					applist.add(info);
				}
			} catch (Exception e) {
				e.printStackTrace();
			}
		}

		return applist;
	}

	private class LoadApplications extends AsyncTask<Void, Void, Void> {
		private ProgressDialog progress = null;

		@Override
		protected Void doInBackground(Void... params) {
			applist = checkForLaunchIntent(packageManager.getInstalledApplications(PackageManager.GET_META_DATA));
			listadaptor = new ApplicationAdapter(AllAppsActivity.this,
					R.layout.snippet_list_row, applist);

			return null;
		}

		@Override
		protected void onCancelled() {
			super.onCancelled();
		}

		@Override
		protected void onPostExecute(Void result) {
			setListAdapter(listadaptor);
			progress.dismiss();
			super.onPostExecute(result);
		}

		@Override
		protected void onPreExecute() {
			progress = ProgressDialog.show(AllAppsActivity.this, null,
					"Loading application info...");
			super.onPreExecute();
		}

		@Override
		protected void onProgressUpdate(Void... values) {
			super.onProgressUpdate(values);
		}
	}
}
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ApplicationAdapter.java

package com.javatechig.listapps;

import java.util.List;

import android.content.Context;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageManager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;

public class ApplicationAdapter extends ArrayAdapter<ApplicationInfo> {
	private List<ApplicationInfo> appsList = null;
	private Context context;
	private PackageManager packageManager;

	public ApplicationAdapter(Context context, int textViewResourceId,
			List<ApplicationInfo> appsList) {
		super(context, textViewResourceId, appsList);
		this.context = context;
		this.appsList = appsList;
		packageManager = context.getPackageManager();
	}

	@Override
	public int getCount() {
		return ((null != appsList) ? appsList.size() : 0);
	}

	@Override
	public ApplicationInfo getItem(int position) {
		return ((null != appsList) ? appsList.get(position) : null);
	}

	@Override
	public long getItemId(int position) {
		return position;
	}

	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
		View view = convertView;
		if (null == view) {
			LayoutInflater layoutInflater = (LayoutInflater) context
					.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
			view = layoutInflater.inflate(R.layout.snippet_list_row, null);
		}

		ApplicationInfo applicationInfo = appsList.get(position);
		if (null != applicationInfo) {
			TextView appName = (TextView) view.findViewById(R.id.app_name);
			TextView packageName = (TextView) view.findViewById(R.id.app_paackage);
			ImageView iconview = (ImageView) view.findViewById(R.id.app_icon);

			appName.setText(applicationInfo.loadLabel(packageManager));
			packageName.setText(applicationInfo.packageName);
			iconview.setImageDrawable(applicationInfo.loadIcon(packageManager));
		}
		return view;
	}
};
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