简易Launcher开发

谁借莪１个温暖的怀抱￠ 2022-06-13 06:59 156阅读 0赞

**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" />**

![ContractedBlock.gif][] 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。**

按 Ctrl+C 复制代码

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

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

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;
            }

![复制代码][copycode.gif]

**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() {
    @Override
    
       
        public
       
         
       
        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：

![复制代码][copycode.gif]

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);
            }

![复制代码][copycode.gif]

最后整个Activity的代码如下：

![ExpandedBlockStart.gif][]

![复制代码][copycode.gif]

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;
            }
        }
    }

![复制代码][copycode.gif]

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