部件視圖還包括一對Java類,他們負責初始化視圖並頻繁更新它,這些Java類負責在主屏幕上管理部件的生命週期。當將部件拖到屏幕上,以及將部件拖到回收站進行卸載時,這些類進行相應。
下面通過一個倫敦奧運會倒計時的簡單Widget例子來說明如何創建一個桌面小部件。
1、定義一個AppWidgetProviderInfo,在/res/xml/widget.xml
<?xml version="1.0" encoding="utf-8"?>
<appwidget-provider
xmlns:android="http://schemas.android.com/apk/res/android"
android:minWidth="50dip"
android:minHeight="50dip"
android:updatePeriodMillis="10000"
android:initialLayout="@layout/main"
>
</appwidget-provider>
2、爲AppWidget指定樣式和佈局:main.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:orientation="vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="倫敦奧運會倒計時"
android:textSize="14px"
android:textColor="#ff00ff"
/>
<TextView
android:id="@+id/Olympic"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello"
android:textSize="16px"
android:textColor="#ff00ff"
android:gravity="center"
/>
<ImageView android:id="@+id/imageView1" android:layout_height="wrap_content" android:src="@drawable/olympic" android:layout_width="wrap_content"></ImageView>
</LinearLayout>
3、實現AppWidgetProvider類
/**
* 簡單widget
* 一般會實現一個BroadcastReceiver當接收到廣播時,更新widget;本例子直接用定時任務實現更新。
* @author fwwdn
*
*/
public class WidgetDemo extends AppWidgetProvider {
@Override
public void onUpdate(Context context, AppWidgetManager appWidgetManager,
int[] appWidgetIds) {
// TODO Auto-generated method stub
Timer timer = new Timer();
timer.scheduleAtFixedRate(new MyTime(context,appWidgetManager), 1, 60000);
super.onUpdate(context, appWidgetManager, appWidgetIds);
}
//定時任務類
private class MyTime extends TimerTask{
RemoteViews remoteViews;
AppWidgetManager appWidgetManager;
ComponentName thisWidget;
public MyTime(Context context,AppWidgetManager appWidgetManager){
this.appWidgetManager = appWidgetManager;
remoteViews = new RemoteViews(context.getPackageName(),R.layout.main);
thisWidget = new ComponentName(context,WidgetDemo.class);
}
//定時任務內容
public void run() {
Date date = new Date();
Calendar calendar = new GregorianCalendar(2012,06,28);
long days = ((calendar.getTimeInMillis()-date.getTime())/(1000*60*60*24));
remoteViews.setTextViewText(R.id.Olympic, "距離2012倫敦奧運會還有" + days+"天");
//更新Widget內容
appWidgetManager.updateAppWidget(thisWidget, remoteViews);
}
}
}
4、在AndroidManifest.xml中註冊:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.test.widget"
android:versionCode="1"
android:versionName="1.0">
<application android:icon="@drawable/icon" android:label="@string/app_name">
<receiver android:name=".WidgetDemo"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
</intent-filter>
<meta-data android:name="android.appwidget.provider"
android:resource="@xml/widget"
/>
</receiver>
</application>
</manifest>
運行程序,長按桌面在談出的選項中選擇窗口小部件,結果如圖:
然後選擇olympic widget,結果如圖所示: