Android:AppWidget，PendingIntent，RemoteViews用法

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什么是AppWidget？AppWidget就是我们平常在桌面上见到的那种一个个的小窗口，利用这个小窗口可以给用户提供一些方便快捷的操作。本篇打算从以下几个点来介绍AppWidget:

      1.如何创建一个简单的AppWidget

      2.如何使得AppWidget与客户端程序交互

下面我们来创建一个简单的AppWidget

1、定义AppWidgetProviderInfor：在res/xml文件夹中定义一个名为 ：example_appwidget_info.xml，这个名字随便取。它是提供AppWidget元数据；设置在桌面上显示的大小 

example_appwidget_info.xml

 

 < appwidget-provider   xmlns:android = "http://schemas.android.com/apk/res/android"
     android:minWidth = "294dp"
     android:minHeight = "72dp"
     android:updatePeriodMillis = "86400000"
     android:initialLayout = "@layout/example_appwidget" >

   appwidget-provider >

2、为App Widget指定样式和布局；在桌面上显示的内容，布局，就像main.xml布局一样，做为example_appwidget_info.xml的 initialLayout参数的值，用这个布局文件来初始化example_appwidget_info.xml。

 

  "1.0"  encoding= "utf-8" ?>
 "http://schemas.android.com/apk/res/android"
     android:orientation="vertical"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent"
     >

     android:id="@+id/widgetTextId"
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:text="firstWidgetText"
     android:background="#000000"
     />

3、实现继承AppWidgetProvider这个类；

这个类有五个方法：都需要继承：（下面按照当第一次加载Widget到删除的时候，这些方法运行的顺序）

1、onReceive (Context  context, Intent  intent)   Implements onReceive(Context, Intent)  to dispatch calls to the various other methods on AppWidgetProvider.

2、onEnabled (Context  context)  Called in response to the ACTION_APPWIDGET_ENABLED  broadcast when the a AppWidget for this provider is instantiated. Override this method to implement your own AppWidget functionality.

3、onUpdate (Context  context, AppWidgetManager  appWidgetManager, int[] appWidgetIds)  Called in response to the ACTION_APPWIDGET_UPDATE  broadcast when this AppWidget provider is being asked to provide RemoteViews  for a set of AppWidgets. Override this method to implement your own AppWidget functionality.

4、onDeleted (Context  context, int[] appWidgetIds)  Called in response to the ACTION_APPWIDGET_DELETED  broadcast when one or more AppWidget instances have been deleted. Override this method to implement your own AppWidget functionality.

5、onDisabled (Context  context)  Called in response to the ACTION_APPWIDGET_DISABLED  broadcast, which is sent when the last AppWidget instance for this provider is deleted. Override this method to implement your own AppWidget functionality.

基中onReceive负责进行接受广播，控制运行哪一个函数，每一个操作都会首先运行这个方法，再调用其它的方法。所以在Widget一次加载到删除过程中，onReceive会执行4次；

如下图：注意message

下面看代码： ExampleAppWidgetProvider.java

 

 public   class  ExampleAppWidgetProvider  extends  AppWidgetProvider {
     @Override
     public   void  onUpdate(Context context, AppWidgetManager appWidgetManager,
             int [] appWidgetIds) {
         System.out.println("onupdate" );
         super .onUpdate(context, appWidgetManager, appWidgetIds);
     }

     @Override
     public   void  onDeleted(Context context,  int [] appWidgetIds) {
         System.out.println("onDeleted" );
         super .onDeleted(context, appWidgetIds);
     }

     @Override
     public   void  onDisabled(Context context) {
         System.out.println("onDisabled" );
         super .onDisabled(context);
     }

     @Override
     public   void  onEnabled(Context context) {
         System.out.println("onEnabled" );
         super .onEnabled(context);
     }
 }

在这个实例中，因为与Activity脱离关系，所以Activity不用更改，只是在应用系统中注册了一个与这个应用程序相关的AppWidget而已：结果：

下面再来看看如何在AppWidget中添加按钮，添加监听事件。

1、在example_appwidget_info.xml文件里添加Button迫使

2、添加TargetActivity

只是用来响应点击事件，在此例中没有实际意义

 public   class  TargetActivity  extends  Activity {
     @Override
     protected   void  onCreate(Bundle savedInstanceState) {
         super .onCreate(savedInstanceState);
         setContentView(R.layout.main);
     }
 }

3、在AndroidManifest.xml文件注册TargetActivity

4、重写ExampleAppWidgetProvider类的onUpdate方法，在第一次创建WidGet的时候，向按钮添加监听。并用PendingIntent，和RemoteView两个类，对事件进行处理；

 

 public   void  onUpdate(Context context, AppWidgetManager appWidgetManager,
             int [] appWidgetIds) {
         System.out.println("onupdated" );

         for  ( int  i =  0 ; i
             System.out.println(appWidgetIds[i]);
             //创建一个Intent对象
             Intent intent = new  Intent(context,TargetActivity. class );
             //创建一个PendingIntent（有四种方法获取）
             PendingIntent pendingIntent = PendingIntent.getActivity(context, 0 , intent,  0 );
             RemoteViews remoteViews = new  RemoteViews(context.getPackageName(),R.layout.example_appwidget);
             //为按钮绑定事件处理器
             //第一个参数用来指定被绑定处理器的控件的ID
             //第二个参数用来指定当事件发生时，哪个PendingIntent将会被执行
             remoteViews.setOnClickPendingIntent(R.id.widgetButton, pendingIntent);
             //更新AppWidget
             //第一个参数用于指定被更新AppWidget的ID
             appWidgetManager.updateAppWidget(appWidgetIds[i], remoteViews);
         }
         super .onUpdate(context, appWidgetManager, appWidgetIds);
     }

 

Called in response to the ACTION_APPWIDGET_DELETED  broadcast when one or more AppWidget instances have been deleted. Override this method to implement your own AppWidget functionality.

在实际应用在AppWidget更多的是利用广播机制Action进行处理的；下面我们来看看如何利用广播机制，单击改变AppWidget的内容；在上例 的基础上进行扩展：

1、AppWidget的布局文件：widget01.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"
     >
 < Button   android:id = "@+id/widgetButton"
     android:layout_width = "fill_parent"
     android:layout_height = "wrap_content"
     android:text = "@string/widget_button" />

 < TextView   android:id = "@+id/test_text"
     android:layout_width = "fill_parent"
     android:layout_height = "wrap_content"
     android:text = "@string/test_text"
     android:gravity = "center"
     android:textColor = "#fff" />
  LinearLayout >

其中的Button控件是测试按钮，TextView用来反应单击Button之后显示的内容变化；（这是给Button添加监听器，再利用Action广播。收onRecerve接收，做出动作）

2、修改AndroidManifest.xml

在Reservi里添加action，注册事件

 < receiver   android:name = "ExampleAppWidgetProvider" >
     < intent-filter >
          < action   android:name = "android.appwidget.action.APPWIDGET_UPDATE" />
         < action   android:name = "learn.test.UPDATE_APP_WIDGET" />
      intent-filter >
     < meta-data   android:name = "android.appwidget.provider"   android:resource = "@xml/widget_test"   />
  receiver >

3、修改ExampleAppWidgetProvider.java代码文件，如下：

 public   class  ExampleAppWidgetProvider  extends  AppWidgetProvider {
     //定义一个常量字符串，该常量用于命名Action
     private   static   final  String UPDATE_ACTION =  "learn.test.UPDATE_APP_WIDGET" ;

     @Override
     public   void  onDeleted(Context context,  int [] appWidgetIds) {
         // TODO Auto-generated method stub
 System.out.println("onDeleted" );
         super .onDeleted(context, appWidgetIds);
     }

     @Override
     public   void  onDisabled(Context context) {
         // TODO Auto-generated method stub
 System.out.println("onDisabled" );
         super .onDisabled(context);
     }

     @Override
     public   void  onEnabled(Context context) {
         // TODO Auto-generated method stub
 System.out.println("onEnabled" );
         super .onEnabled(context);
     }

     @Override
     public   void  onReceive(Context context, Intent intent) {
         // TODO Auto-generated method stub
 System.out.println("onReceive" );

         String action = intent.getAction();
         if  (UPDATE_ACTION.equals(action)) {
             RemoteViews remoteViews = new  RemoteViews(context.getPackageName(),
                     R.layout.widget01);
             remoteViews.setTextViewText(R.id.test_text, "this is OnReceive" );
             //getInstance(Context context)  Get the AppWidgetManager instance to use for the supplied Context object.静态方法。
             AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context);

             ComponentName componentName = new  ComponentName(context,ExampleAppWidgetProvider. class );
             appWidgetManager.updateAppWidget(componentName, remoteViews);
         } else  {
             super .onReceive(context, intent); 这里一定要添加，eles部分，不然，onReceive不会去调用其它的方法。但是如果把这条语句放在外面，就会每次运行 onUpdate,onDeleted等方法，就会运行两次，因为UPDATE_ACTION.equals(action)配置成功会运行一 次，uper.onReceive(context, intent)配置成功又会运行一次，后都是系统自定义的。
         }
     }

     @Override
     public   void  onUpdate(Context context, AppWidgetManager appWidgetManager,
             int [] appWidgetIds) {
         // TODO Auto-generated method stub
 System.out.println("onUpdated" );

 //创建一个Intent对象
         Intent intent = new  Intent();
         //为Intent对象设置Action
         intent.setAction(UPDATE_ACTION);
         //使用getBroadcast方法，得到一个PendingIntent对象，当该对象执行时，会发送一个广播
         PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0 ,
                 intent, 0 );
         RemoteViews remoteViews = new  RemoteViews(context.getPackageName(),
                 R.layout.widget01);

         remoteViews.setOnClickPendingIntent(R.id.widgetButton, pendingIntent);
         appWidgetManager.updateAppWidget(appWidgetIds, remoteViews);
         super .onUpdate(context, appWidgetManager, appWidgetIds);
     }

 }