Android:AppWidget，PendingIntent，RemoteViews用法
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">
<!-- initiallayout设置引用 的布局文件 -->
</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。
<?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"
>
<TextView
android:id="@+id/widgetTextId"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="firstWidgetText"
android:background="#000000"
/>
</LinearLayout>
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 <appWidgetIds.length; 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"><!--如果action匹配成功，就在此类中进行处理--> <intent-filter> <!--利用广播机制接收,onUpdate会接收广播。查看源码可收得知 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. 这个也必须要，不然onRecerve不会调用 。--> <!--这是自定义的Action事件--><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);
}
}