TimeChangeReceiver: Ensure the alarm is set

Ensure TimeChangeReceiver alarm is scheduled when enabling
datetime_synconconnect and registering TimeChangeReceiver broadcast
receiver.

It is important to re-schedule the alarm after registering broadcast
receiver, because:
1. if broadcast receiver was unregistered while previous alarm arrived,
there is no alarm scheduled;
2. re-scheduling the alarm resets the periodic time sync timer when
first device is connected (which is desired).

It is important to re-schedule the alarm when datetime_synconconnect
gets enabled, because there might be no alarm scheduled.

Call onSetTime() when enabling datetime_synconconnect.

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/GBApplication.java

@@ -246,7 +246,6 @@ public class GBApplication extends Application {
         loadAppsPebbleBlackList();
 
         PeriodicExporter.enablePeriodicExport(context);
-        TimeChangeReceiver.scheduleNextDstChangeOrPeriodicSync(context);
 
         if (isRunningMarshmallowOrLater()) {
             notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/activities/SettingsActivity.java

@@ -71,6 +71,7 @@ import nodomain.freeyourgadget.gadgetbridge.devices.miband.MiBandPreferencesActi
 import nodomain.freeyourgadget.gadgetbridge.devices.pebble.PebbleSettingsActivity;
 import nodomain.freeyourgadget.gadgetbridge.devices.qhybrid.ConfigActivity;
 import nodomain.freeyourgadget.gadgetbridge.devices.zetime.ZeTimePreferenceActivity;
+import nodomain.freeyourgadget.gadgetbridge.externalevents.TimeChangeReceiver;
 import nodomain.freeyourgadget.gadgetbridge.model.Weather;
 import nodomain.freeyourgadget.gadgetbridge.util.AndroidUtils;
 import nodomain.freeyourgadget.gadgetbridge.util.FileUtils;
@@ -173,6 +174,17 @@ public class SettingsActivity extends AbstractSettingsActivityV2 {
                 });
             }
 
+            pref = findPreference("datetime_synconconnect");
+            if (pref != null) {
+                pref.setOnPreferenceChangeListener((preference, newVal) -> {
+                    if (Boolean.TRUE.equals(newVal)) {
+                        TimeChangeReceiver.scheduleNextDstChangeOrPeriodicSync(requireContext());
+                        GBApplication.deviceService().onSetTime();
+                    }
+                    return true;
+                });
+            }
+
             pref = findPreference("log_to_file");
             if (pref != null) {
                 pref.setOnPreferenceChangeListener((preference, newVal) -> {

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/externalevents/TimeChangeReceiver.java

@@ -143,6 +143,12 @@ public class TimeChangeReceiver extends BroadcastReceiver {
         }
     }
 
+    public static void ifEnabledScheduleNextDstChangeOrPeriodicSync(final Context context) {
+        if (GBApplication.getPrefs().getBoolean("datetime_synconconnect", true)) {
+            scheduleNextDstChangeOrPeriodicSync(context);
+        }
+    }
+
     private static boolean canScheduleExactAlarms(final Context context, final AlarmManager am) {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
             return am.canScheduleExactAlarms();

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/DeviceCommunicationService.java

@@ -1181,6 +1181,9 @@ public class DeviceCommunicationService extends Service implements SharedPrefere
                 filter.addAction("android.intent.action.TIMEZONE_CHANGED");
                 filter.addAction(TimeChangeReceiver.ACTION_DST_CHANGED_OR_PERIODIC_SYNC);
                 registerReceiver(mTimeChangeReceiver, filter);
+                // Ensure alarm is scheduled after registering broadcast receiver
+                // (this is important in case receiver was unregistered when the previous alarm arrived).
+                TimeChangeReceiver.ifEnabledScheduleNextDstChangeOrPeriodicSync(this);
             }
             if (mBlueToothPairingRequestReceiver == null) {
                 mBlueToothPairingRequestReceiver = new BluetoothPairingRequestReceiver(this);