Android的Widget编写实例

Android有个非常好的功能，就是Widget控件，Widget作为应用的快捷方式和缩略展示，它在桌面上可以展示用户感兴趣的应用程序提供的信息，并且可以点击widget上的控件从而进入到应用的Activity。那么怎么去开发一个Widget呢，可以说是非常的人性化和方便的。下面是我在学习中创建的一个小实例。

参照Google的文档，我们首先得在清单文件中declare一个widget，代码如下。

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

下面我们要去写一个类ExampleAppWidgetProvider它要继承AppWidgetProvider，还有我们注意这行：android:resource="@xml/example_appwidget_info，example_appwidget_info.xml是用来描述控件的元数据。下面分别给出相应的代码。

example_appwidget_info.xml

<?xml version="1.0" encoding="utf-8"?><appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"    android:minWidth="294dp"    android:minHeight="72dp"    android:updatePeriodMillis="0"    android:initialLayout="@layout/example_appwidget"    ></appwidget-provider>

ExampleAppWidgetProvider.java

package cn.itcast.widget;import java.text.SimpleDateFormat;import java.util.Date;import android.appwidget.AppWidgetManager;import android.appwidget.AppWidgetProvider;import android.content.Context;import android.content.Intent;import android.util.Log;import android.widget.RemoteViews;public class ExampleAppWidgetProvider extends AppWidgetProvider {@Overridepublic void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {super.onUpdate(context, appWidgetManager, appWidgetIds);Log.i("i", "onUpdate()");RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.example_appwidget);Date date = new Date(System.currentTimeMillis());SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");String time = format.format(date);views.setTextViewText(R.id.tv_time, time);appWidgetManager.updateAppWidget(appWidgetIds[0], views);}@Overridepublic void onDeleted(Context context, int[] appWidgetIds) {super.onDeleted(context, appWidgetIds);Log.i("i", "onDeleted()");}@Overridepublic void onEnabled(Context context) {super.onEnabled(context);Log.i("i", "onEnabled()");// 启动服务Intent intent = new Intent(context, UpdateTimeService.class);context.startService(intent);}@Overridepublic void onDisabled(Context context) {super.onDisabled(context);Log.i("i", "onDisabled()");// 停止服务Intent intent = new Intent(context, UpdateTimeService.class);context.stopService(intent);}}

如下XML文件是widget的布局文件，

<?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"     android:background="#fff">    <TextView android:id="@+id/tv_time"        android:layout_width="fill_parent"        android:layout_height="fill_parent"        android:text="我是widget"        android:textColor="#f00"/></LinearLayout>

下面这个类是一个service，它负责实时更新桌面上widget显示的时间，具体代码如下，

import java.text.SimpleDateFormat;import java.util.Date;import java.util.Timer;import java.util.TimerTask;import android.app.PendingIntent;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 UpdateTimeService extends Service {private Timer timer;private TimerTask task = new TimerTask() {@Overridepublic void run() {// 得到widget管理器AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(getApplicationContext());ComponentName componentName = new ComponentName(getApplicationContext(), ExampleAppWidgetProvider.class);RemoteViews views = new RemoteViews(getPackageName(), R.layout.example_appwidget);Date date = new Date(System.currentTimeMillis());SimpleDateFormat formate = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");String time = formate.format(date);views.setTextViewText(R.id.tv_time, time);Intent intent = new Intent(getApplicationContext(), MainActivity.class);PendingIntent pendingIntent = PendingIntent.getActivity(getApplicationContext(), 100, intent, 0);// 设置widget的点击事件views.setOnClickPendingIntent(R.id.tv_time, pendingIntent);// 更新widgetappWidgetManager.updateAppWidget(componentName, views);}};@Overridepublic void onCreate() {super.onCreate();timer = new Timer();timer.schedule(task, 0, 1000);// 开始任务}@Overridepublic IBinder onBind(Intent intent) {return null;}@Overridepublic void onDestroy() {super.onDestroy();timer.cancel();// 结束任务}}

清单文件中注册service，加上：

<service android:name=".UpdateTimeService"></service>

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