Android中Launcher实例

Launcher是Android的应用程序启动器，Launcher的功能 还包含：桌面的切换、应用程序快捷 (shortcut)功能、背景图(Wallpaper)功能等等。在Android的桌面最下方，有一个图示，按下后可以拉出应用程序图示清单，这是Launcher提供的功能。

我们这个实例是用GridView来实现Launcher效果的， 下面的截屏显示本实例的效果图：

源代码如下：

main.xml布局文件，只有一个GridView:

<?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">
    
	<GridView
		android:id="@+id/gridview"
		android:layout_width="fill_parent"
		android:layout_height="wrap_content"/>
		
</LinearLayout>

GridView的每一个Item也需要一个布局文件，用来定义应用的图标与标题，application_layout.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">
    
	<ImageView
		android:id="@+id/imageview"
		android:layout_width="wrap_content"
		android:layout_height="wrap_content"/>
	<TextView
		android:id="@+id/textview"
		android:layout_width="wrap_content"
		android:layout_height="wrap_content"/>
		
</LinearLayout>

主程序文件，Launcher.java:

package com.test.launcher;
import java.util.Collections;
import java.util.List;
import android.app.Activity;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.AdapterView.OnItemClickListener;
public class Launcher extends Activity implements OnItemClickListener {
	private GridView mGridView;
	private Context mContext;
	private PackageManager mPackageManager;
	private List<ResolveInfo> mAllApps;
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		setupViews();
	}
	public void setupViews() {
		mContext = Launcher.this;
		mPackageManager = getPackageManager();
		mGridView = (GridView) findViewById(R.id.gridview);
		bindAllApps();
		// GridView中放入数据
		mGridView.setAdapter(new GridItemAdapter(mContext, mAllApps));
		mGridView.setNumColumns(4);
		mGridView.setOnItemClickListener(this);
	}
	public void bindAllApps() {
		// 应用中总有一个activity申明成这两个属性,也就是应用的入口
		Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);
		mainIntent.addCategory(Intent.CATEGORY_LAUNCHER);
		// 包含上面两个属性的全部查出来,并且排序
		mAllApps = mPackageManager.queryIntentActivities(mainIntent, 0);
		Collections.sort(mAllApps, new ResolveInfo.DisplayNameComparator(
				mPackageManager));
	}
	@Override
	public void onItemClick(AdapterView<?> parent, View view, int position,
			long id) {
		ResolveInfo res = mAllApps.get(position);
		// 该应用的包名和主Activity
		String pkg = res.activityInfo.packageName;
		String cls = res.activityInfo.name;
		ComponentName componet = new ComponentName(pkg, cls);
		Intent intent = new Intent();
		intent.setComponent(componet);
		startActivity(intent);
	}
	private class GridItemAdapter extends BaseAdapter {
		private Context context;
		private List<ResolveInfo> resInfo;
		public GridItemAdapter(Context c, List<ResolveInfo> res) {
			context = c;
			resInfo = res;
		}
		@Override
		public int getCount() {
			return resInfo.size();
		}
		@Override
		public Object getItem(int position) {
			return null;
		}
		@Override
		public long getItemId(int position) {
			return 0;
		}
		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			convertView = LayoutInflater.from(context).inflate(
					R.layout.application_layout, null);
			ImageView imageView = (ImageView) convertView
					.findViewById(R.id.imageview);
			TextView textView = (TextView) convertView
					.findViewById(R.id.textview);
			ResolveInfo res = resInfo.get(position);
			imageView.setImageDrawable(res.loadIcon(mPackageManager));
			textView.setText(res.loadLabel(mPackageManager).toString());
			return convertView;
		}
	}
}

几点说明：

1. 函数setupViews（）是建立Launcher桌面的Views的。setupViews里面的函数bindAllApps（）是把Activity里面所有符合特定Intent的结果查出来，结果封装在ResolveInfo的List里面。可以通过ResolveInfo获取到应用的图标及标签。
2. 包android.content.pm所含的类负责获取应用程序包的信息，包括关于activities,permissions,services,signatures和providers的信息。