一、簡介
桌面小部件,是android提供支持的一種特殊廣播,允許在桌面以插件的形式展示內容。
二、示例
1、創建佈局文件:此處的佈局只使用一個簡單的TextView
/layout/layout_widget.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:gravity="center"
android:orientation="vertical" >
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="0000-00-00 00:00:00"
android:textColor="@android:color/background_dark" >
</TextView>
</LinearLayout>
2、創建AppWidgetProvider的子類
import java.text.SimpleDateFormat;
import java.util.Date;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.appwidget.AppWidgetManager;
import android.appwidget.AppWidgetProvider;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.widget.RemoteViews;
import com.am.appwidget.R;
public class TimeWidgetProvider extends AppWidgetProvider {
private final String UPDATE_ACTION = "TimeWidgetProvider.update.date";
// 收到請求時執行
@Override
public void onReceive(Context context, Intent intent) {
System.out.println("===onReceive");
if (intent != null && UPDATE_ACTION.equals(intent.getAction())) {
updateViews(context);
}
super.onReceive(context, intent);
}
@Override
public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
System.out.println("===onUpdate");
// 設置定時任務,定時刷新widget
StartAlarm(context);
}
// 刪除時調用
@Override
public void onDeleted(Context context, int[] appWidgetIds) {
System.out.println("===onDeleted");
stopAlarm(context);
}
private void StartAlarm(Context context) {
Intent intent = new Intent(context, TimeWidgetProvider.class);
intent.setAction(UPDATE_ACTION);
// AppWidgetProvider 是 BroadcastReceiver 的子類
PendingIntent refreshIntent = PendingIntent.getBroadcast(context, 0, intent, 0);
AlarmManager alarm = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
alarm.setRepeating(AlarmManager.RTC, 0, 1000, refreshIntent);
}
private void stopAlarm(Context context) {
Intent intent = new Intent(context, TimeWidgetProvider.class);
intent.setAction(UPDATE_ACTION);
PendingIntent refreshIntent = PendingIntent.getBroadcast(context, 0, intent, 0);
AlarmManager alarm = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
alarm.cancel(refreshIntent);
}
private void updateViews(Context context) {
// 只能通過遠程對象來設置appwidget中的控件狀態
SimpleDateFormat sf = new SimpleDateFormat("yyy-MM-dd HH:mm:ss");
String date = sf.format(new Date());
RemoteViews remoteViews = new RemoteViews(context.getPackageName(), R.layout.layout_widget);
remoteViews.setTextViewText(R.id.textView1, date);
// 獲得appwidget管理實例,用於管理appwidget以便進行更新操作
AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context);
// 相當於獲得所有本程序創建的appwidget
ComponentName componentName = new ComponentName(context, TimeWidgetProvider.class);
// 更新appwidget
appWidgetManager.updateAppWidget(componentName, remoteViews);
}
}
3、創建Appwidget的配置文件/xml/provider_config.xml
<?xml version="1.0" encoding="utf-8"?>
<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
android:initialLayout="@layout/layout_widget"
android:minHeight="40dp"
android:minWidth="80dp"
android:updatePeriodMillis="0" >
<!-- updatePeriodMillis:官網的意思如果更新頻率大於一次/小時會造成電池壽命問題,設置小了也不起作用,所以在此使用0也就是不更新,後臺使用定時任務刷新 -->
</appwidget-provider>
4、配置AndroidManifest.xml
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
... ...
<!-- 配置AppWidgetProvider -->
<receiver
android:name="com.am.appwidget.widget.TimeWidgetProvider"
android:label="Time App Widget" >
<!-- 必須顯示聲明以下action -->
<intent-filter>
<action android:name="android.appwidget.action.APPWIDGET_UPDATE" >
</action>
</intent-filter>
<!-- 指定widget的配置文件路徑 -->
<meta-data
android:name="android.appwidget.provider"
android:resource="@xml/provider_config" />
</receiver>
</application>
三、結果