编写android的widget

以前对这个东西很感兴趣，因为确实方便，如今有时间了来做一个例子

首先要定义一个layout(widgetview.xml)和一个配置文件(widgetconfig.xml)

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical" >

     <TextView
         android:id="@+id/tv"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:text="时间显示" />

 </LinearLayout>

 <?xml version="1.0" encoding="utf-8"?>
 <appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
     android:initialLayout="@layout/widget"
     android:minHeight="40dp"
     android:minWidth="100dp"
     android:updatePeriodMillis="864000" >

 </appwidget-provider>

然后再实现一个widgetProvider

 package com.example.widgettest;

 import android.appwidget.AppWidgetManager;
 import android.appwidget.AppWidgetProvider;
 import android.content.Context;
 import android.content.Intent;

 public class WidgetProvider extends AppWidgetProvider {
     @Override
     public void onDeleted(Context context, int[] appWidgetIds) {
         super.onDeleted(context, appWidgetIds);
         // widget被移除
     }

     @Override
     public void onDisabled(Context context) {
         super.onDisabled(context);
         // 最后一个被移除
         context.stopService(new Intent(context, TimerService.class));
     }

     @Override
     public void onEnabled(Context context) {
         super.onEnabled(context);
         // widget添加到屏幕上
         context.startService(new Intent(context, TimerService.class));
     }

     @Override
     public void onReceive(Context context, Intent intent) {
         super.onReceive(context, intent);
     }

     @Override
     public void onUpdate(Context context, AppWidgetManager appWidgetManager,
             int[] appWidgetIds) {
         super.onUpdate(context, appWidgetManager, appWidgetIds);
         // 刷新widget
     }
 }

通过一个service对provider进行刷新

 package com.example.widgettest;

 import java.text.SimpleDateFormat;
 import java.util.Date;
 import java.util.Timer;
 import java.util.TimerTask;

 import android.app.Service;
 import android.appwidget.AppWidgetManager;
 import android.content.ComponentName;
 import android.content.Intent;
 import android.os.IBinder;
 import android.widget.RemoteViews;

 public class TimerService extends Service {
     private Timer timer;
     private SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

     @Override
     public IBinder onBind(Intent intent) {
         // TODO Auto-generated method stub
         return null;
     }

     @Override
     public void onCreate() {
         // TODO Auto-generated method stub
         super.onCreate();

         timer = new Timer();
         timer.schedule(new TimerTask() {

             @Override
             public void run() {
                 updateViews();
             }
         }, 0, 1000);
     }

     private void updateViews() {
         String time = sdf.format(new Date());
         RemoteViews rv = new RemoteViews(getPackageName(), R.layout.widget);
         rv.setTextViewText(R.id.tv, time);
         AppWidgetManager manager = AppWidgetManager
                 .getInstance(getApplicationContext());
         ComponentName cn = new ComponentName(getApplicationContext(),
                 WidgetProvider.class);
         manager.updateAppWidget(cn, rv);
     }

     @Override
     public void onDestroy() {
         // TODO Auto-generated method stub
         super.onDestroy();
         timer = null;
     }

 }

最后要注册AndroidManifest文件

 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.example.widgettest"
     android:versionCode="1"
     android:versionName="1.0" >

     <uses-sdk
         android:minSdkVersion="8"
         android:targetSdkVersion="23" />

     <application
         android:allowBackup="true"
         android:icon="@drawable/ic_launcher"
         android:label="@string/app_name" >
         <activity
             android:name=".MainActivity"
             android:label="@string/app_name" >
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />

                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>

         <service android:name="com.example.widgettest.TimerService" >
         </service>

         <receiver android:name="com.example.widgettest.WidgetProvider" >
             <intent-filter>
                 <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
             </intent-filter>

             <meta-data
                 android:name="android.appwidget.provider"
                 android:resource="@xml/widgetconfig" />
         </receiver>
     </application>

 </manifest>