Calendar Notification Issue with DavX

[AnyByte]

Summary:

I have encountered an issue with calendar notifications while using DavX to sync my CalDav calendar. Despite setting the default reminder to 3 minutes in DavX, the notifications are not functioning correctly in both Google Calendar and Samsung Calendar.

Details:

1. Google Calendar Behavior: The notification setting appears correctly as "3 minutes before" for events. However, despite this correct display, the calendar does not issue any actual notifications.
2. Samsung Calendar Behavior: There's an inconsistency in the notification display. Initially, the notification setting shows an empty line. Only upon editing, it reveals that a 3-minute notification is selected. However, closing this view reverts to showing an empty space for the notification setting, which is unusual.
3. Notification Functionality Issue: Both Google and Samsung calendars completely ignore the 3-minute notification setting. Tests conducted, including setting Samsung Calendar to display full-screen alerts with extended sounds, resulted in no notifications being received. In contrast, creating events directly in Google or Samsung calendars triggers alerts as expected.

Conclusion:

This leads to the suspicion that DavX might be synchronizing alerts in a manner that results in silent or non-functional notifications. Your insights on this would be valuable. Do you think the issue lies with DavX's synchronization process?

[sunkup]

Thanks for the report. I can confirm a default reminder is being added to events which are not full day length. However they seem not to show up as notifications.

More testing needed.

Issue: #492

[rfc2822]

Seems that Android only shows alerts for METHOD_ALERT: https://android.googlesource.com/platform/packages/providers/CalendarProvider/+/refs/heads/main/src/com/android/providers/calendar/CalendarAlarmManager.java#325

DAVx⁵ creates the default reminder without a specific action, which is then mapped to METHOD_DEFAULT by ical4android.

Maybe we should

• explicitly set ACTION:DISPLAY for the default reminder → Fix notifications of added default reminders not being shown  #493,
• document the difference between METHOD_ALERT and METHOD_DEFAULT in the ical4android source code,