[英]how to update widget only if wifi state changes?
在學習完本教程之后,我迅速創建了一個簡單的小部件,該小部件每秒在主屏幕上顯示和更新當前時間:
問題:我想知道如何更改此代碼,以便僅在發生特定事件時才更新時間。 例如: 僅在wifi狀態更改時才更新時間 。
這是(希望)相關的代碼部分:
<!-- Broadcast Receiver -->
<receiver android:name=".WifiSSIDWidget" 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/wifi_ssid_widget_provider" />
</receiver>
這是小部件類代碼:
public class HelloWidget extends AppWidgetProvider {
@Override
public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
Timer timer = new Timer();
timer.scheduleAtFixedRate(new MyTime(context, appWidgetManager), 1, 1000);
}
private class MyTime extends TimerTask {
RemoteViews remoteViews;
AppWidgetManager appWidgetManager;
ComponentName thisWidget;
DateFormat format = SimpleDateFormat.getTimeInstance(SimpleDateFormat.MEDIUM, Locale.getDefault());
public MyTime(Context context, AppWidgetManager appWidgetManager) {
this.appWidgetManager = appWidgetManager;
remoteViews = new RemoteViews(context.getPackageName(), R.layout.main);
thisWidget = new ComponentName(context, HelloWidget.class);
}
@Override
public void run() {
remoteViews.setTextViewText(R.id.widget_textview, "TIME = " +format.format(new Date()));
appWidgetManager.updateAppWidget(thisWidget, remoteViews);
}
}
}
要在發生某個事件時觸發,請在清單文件中創建一個broastcast receiver
(請注意,並非所有事件都會觸發,例如:可以接收SMS,但不能發送SMS)。
這是網絡狀態更改的示例。
1)創建一個廣播接收器:
public class NetworkStateChangeReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
Log.i(TAG, "Receive Network State Change");
// you put your main code here.
// or if you don't want, put your code to service. So, run following code
Intent myIntent = new Intent(context, NetworkStateChangeService .class);
// put all intent data to this intent
myIntent.putExtras(intent);
WakefulIntentService.sendWakefulWork(context, myIntent);
}
}
2)此廣播廣播接收器將運行NetworkStateChangeService
代碼。 這是NetworkStateChangeService
的主要代碼:
public class NetworkStateChangeService extends WakefulIntentService {
public static String TAG = "SMS Service";
public NetworkStateChangeService() {
super("Network state change");
}
public SMSReceivedService(String name) {
super(name);
}
@Override
protected void doWakefulWork(Intent intent) {
// put your main code here
}
}
注意: WakefulIntentService
是commonsguy
發明的自定義類
3)您在清單文件中注冊接收器和服務:
<receiver android:name="NetworkStateChangeReceiver ">
<intent-filter>
<action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
</intent-filter>
</receiver>
<service
android:name="NetworkStateChangeService">
</service>
如果要使用Broastcast Receiver
通常是上面的框架。 如您所見,還有一些更簡單的教程,它們只是將主要代碼放在broadcast receiver
onreceive
上,但是如果您的工作花費很長時間,則應該投入使用,並應使用WakefulIntentService
因為它可以幫助設備在工作時喚醒。
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