Repeated refresh

All app widget instances are managed by a corresponding "widget provider" class:

public class MyWidgetProvider extends AppWidgetProvider

The widget provider class will be triggered by the Android operating system when to refresh all instantiated widgets:

    // this method is called in regular time intervals to allow a refresh of the widget's contents
    @Override
    public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds)
    {
        // Get actualized info about next alarm and adjust notification for lock screen
        AlarmInfo alarmInfo = CheckForNextAlarm(context);
        RefreshNotificationForLockScreen(context, alarmInfo);

        // Iterate over all widget instances to actualize their alarm info
        final int numWidgets = appWidgetIds.length;
        for (int i=0; i < numWidgets; i++) {

            int widgetId = appWidgetIds[i];
            RemoteViews remoteViews = new RemoteViews(context.getPackageName(), R.layout.my_widget);

            // Actualize text display.
            String displayText;
            if (alarmInfo.alarmTime.isEmpty())
            {
                displayText = "\noff";
            }
            else // alarm is set
            {
                // Build info text like:
                // So. 7:30
                // (114 h)
                displayText = alarmInfo.alarmTime + " \n(" + alarmInfo.durationUntilAlarm + ")";
            }
            remoteViews.setTextViewText(R.id.text, displayText);

            Intent intent = new Intent(context, MyWidgetProvider.class);
            intent.setAction(AppWidgetManager.ACTION_APPWIDGET_UPDATE);
            intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_IDS, appWidgetIds);

            // Define a refresh action on button click
            PendingIntent pendingIntent = PendingIntent.getBroadcast(context,0, intent,
                    PendingIntent.FLAG_UPDATE_CURRENT);
            remoteViews.setOnClickPendingIntent(R.id.refreshImageBtn, pendingIntent);

            appWidgetManager.updateAppWidget(widgetId,remoteViews);
        }
    }