Android Launcher -- 简易Launcher开发

第一步，把我们的应用程序作为home（即实现按下home键，启动自己的launcher.）

要把我们的应用程序作为home，只需要在AndroidManifest.xml中添加：
 <category android:name="android.intent.category.HOME" />
 <category android:name="android.intent.category.DEFAULT" />

AndroidManifest.xml

第二步，列出安装的应用程序

列出已经安装的应用程序是作为launcher比不可少的功能。下面我们就讲解怎样将应用程序列出来。程序运行后的样子如下：

1. 修改main.xml，在其中添加一个GridView用来显示应用程序列表。

main.xml

2 . 通过PackageManager的api 查询已经安装的apk

private void loadApps() {        Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);        mainIntent.addCategory(Intent.CATEGORY_LAUNCHER);         mApps = getPackageManager().queryIntentActivities(mainIntent, 0);    }

3. 实现用于显示Gridview的Adapter，使其显示获得的应用程序列表

View Code

4.监听GridView的onItemClick事件

设置一个监听器是为了当gridView的某项被点击时，会有一个回调函数通知我们。
我们调用mGrid.setOnItemClickListener(listener); 设置一个监听器
mGrid.setOnItemClickListener(listener)中的listener是一个接口，其类型为：android.widget.AdapterView.OnItemClickListener

private OnItemClickListener listener = new OnItemClickListener() {@Overridepublic void onItemClick(AdapterView<?> parent, View view, int position,long id) {//事件内容....}};

5.启动被点击应用的activity

一般来讲，我们根据position即可知道被点击的项目是哪一项了。现在我们根据被点击的项目，取出对应的应用程序数据（主要是其中的主activity），然后启动activity。用下面代码实现：

 public void onItemClick(AdapterView<?> parent, View view, int position,long id) {            ResolveInfo info = mApps.get(position);                         //该应用的包名            String pkg = info.activityInfo.packageName;            //应用的主activity类            String cls = info.activityInfo.name;                         ComponentName componet = new ComponentName(pkg, cls);                         Intent i = new Intent();            i.setComponent(componet);            startActivity(i);        }

最后整个Activity的代码如下：

package org.bangchui.myhome;import java.util.List;import android.app.Activity;import android.content.ComponentName;import android.content.Intent;import android.content.pm.ResolveInfo;import android.os.Bundle;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.AdapterView.OnItemClickListener;public class MyHome extends Activity {    private List<ResolveInfo> mApps;    GridView mGrid;    private OnItemClickListener listener = new OnItemClickListener() {        @Override        public void onItemClick(AdapterView<?> parent, View view, int position,long id) {            ResolveInfo info = mApps.get(position);                        //该应用的包名            String pkg = info.activityInfo.packageName;            //应用的主activity类            String cls = info.activityInfo.name;                        ComponentName componet = new ComponentName(pkg, cls);                        Intent i = new Intent();            i.setComponent(componet);            startActivity(i);        }    };    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        loadApps();        setContentView(R.layout.main);        mGrid = (GridView) findViewById(R.id.apps_list);        mGrid.setAdapter(new AppsAdapter());        mGrid.setOnItemClickListener(listener);    }    private void loadApps() {        Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);        mainIntent.addCategory(Intent.CATEGORY_LAUNCHER);        mApps = getPackageManager().queryIntentActivities(mainIntent, 0);    }    public class AppsAdapter extends BaseAdapter {        public AppsAdapter() {        }        public View getView(int position, View convertView, ViewGroup parent) {            ImageView i;            if (convertView == null) {                i = new ImageView(MyHome.this);                i.setScaleType(ImageView.ScaleType.FIT_CENTER);                i.setLayoutParams(new GridView.LayoutParams(50, 50));            } else {                i = (ImageView) convertView;            }            ResolveInfo info = mApps.get(position);            i.setImageDrawable(info.activityInfo.loadIcon(getPackageManager()));            return i;        }        public final int getCount() {            return mApps.size();        }        public final Object getItem(int position) {            return mApps.get(position);        }        public final long getItemId(int position) {            return position;        }    }}