android手把手教你开发launcher（三）——启动安装的应用程序

1. 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appsGrid.setOnItemClickListener(listener); 设置一个监听器
appsGrid.setOnItemClickListener(listener)中的listener是一个接口，其类型为：android.widget.AdapterView.OnItemClickListener

下面我们new一个android.widget.AdapterView.OnItemClickListener类型的对象作为参数。我们直接使用eclipde的自动补全功能来完成OnItemClickListener 的定义：

private OnItemClickListener listener = new OnItemClickListener() {        @Override        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {        }    }

接口OnItemClickListener 中有一个方法叫做onItemClick，我们实现它即可。下面我对onItemClick的几个参数略作说明：
parent 略
view被点击的view
position 被点击项的位置
id 被点击项的id

2.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：
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private OnItemClickListener clickListener = new OnItemClickListener() {        @Override        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {            ResolveInfo info = apps.get(i);            //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 intent = new Intent();            intent.setComponent(componet);            startActivity(intent);        }    };

private OnItemClickListener clickListener = new OnItemClickListener() {        @Override        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {            ResolveInfo info = apps.get(i);            //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 intent = new Intent();            intent.setComponent(componet);            startActivity(intent);        }    };

代码中的中文注释可能会引起Gradle报错

解决办法：http://blog.csdn.net/sljjyy/article/details/11976099

现在整个类代码如下：

package com.sljjyy.sao.launcher;import android.content.ComponentName;import android.content.Intent;import android.content.pm.ResolveInfo;import android.os.Bundle;import android.app.Activity;import android.view.Menu;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;import java.util.List;public class MainActivity extends Activity {    GridView appsGrid;    private List<ResolveInfo> apps;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        loadApps();        appsGrid = (GridView) findViewById(R.id.apps_list);        appsGrid.setAdapter(new AppsAdapter());        appsGrid.setOnItemClickListener(clickListener);    }    @Override    public boolean onCreateOptionsMenu(Menu menu) {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater().inflate(R.menu.main, menu);        return true;    }    private OnItemClickListener clickListener = new OnItemClickListener() {        @Override        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {            ResolveInfo info = apps.get(i);            //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 intent = new Intent();            intent.setComponent(componet);            startActivity(intent);        }    };    private void loadApps() {        Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);        mainIntent.addCategory(Intent.CATEGORY_LAUNCHER);        new ImageView(MainActivity.this);        apps = getPackageManager().queryIntentActivities(mainIntent, 0);    }    public class AppsAdapter extends BaseAdapter {        public AppsAdapter(){        }        @Override        public int getCount() {            return apps.size();        }        @Override        public Object getItem(int i) {            return apps.get(i);        }        @Override        public long getItemId(int i) {            return i;        }        @Override        public View getView(int i, View view, ViewGroup viewGroup) {            ImageView iv;            if(view == null){                iv = new ImageView(MainActivity.this);                iv.setScaleType(ImageView.ScaleType.FIT_CENTER);                iv.setLayoutParams(new GridView.LayoutParams(50, 50));            } else {                iv = (ImageView) view;            }            ResolveInfo info = apps.get(i);            iv.setImageDrawable(info.activityInfo.loadIcon(getPackageManager()));            return iv;        }    }}

android手把手教你开发launcher（一）（AndroidStudio版）

android手把手教你开发launcher（二）——列出安装的应用程序

android手把手教你开发launcher（三）——启动安装的应用程序

android手把手教你开发launcher（四）——显示widget

android手把手教你开发launcher（五）——设置壁纸

转自：http://www.bangchui.org/read.php?tid=12208

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