Today I finally could isolate an error that keeps bothering me for about half a year.
My company uses Horde Groupware for calendar and task synchronisation, I am a heavy user of the tasks feature. Thunderbird on Desktop, DAVDroid with the org.dmfs.tasks app on Android phone. If I create an empty task list in Horde and fill it with tasks from my phone, everything works fine (tasks show up everywhere, can be read, modified, marked completed on all devices).
At some point in time, syncing on Android stopped working with a “NumberFormatException” message, pretty much the same as described in https://forums.bitfire.at/topic/1729/numberformatexception-in-1-11-ose. Unfortunately I could not find out how I got there but I can reproduce it the following way:
- Create an empty task list in Horde Groupware
- Move some tasks from the old task list to the freshly created one using either Horde web interface or Thunderbird (on Linux)
- Create a new task on Android
- Press the sync button on Android. Synchronisation fails with the following message: 0_1539037687398_debug.txt
- As soon as I identify the task in the Horde web GUI and move it to another collection the problem disappears.
Additional info: In Horde Web GUI I can see that tasks created with OpenTasks app on Android do not have a priority set by default. Tasks edited in Horde are “upgraded” to a priority. If I move a task to another collection (by pressing “Edit” in the web interface and changing the associated task list) it is assigned a default priority of 1. As I see the debug log mentioning
net.fortuna.ical4j.model.property.Priority.setValue(Priority.java:218) I thought that might be relevant.
In the other topic that I linked above it is said that the reason might be an invalid task file. I doubt that, at least in my case, because I can reproduce the error with a fresh task.
I hope that is enough information, I am happy to provide more if someone can help me get my tasks back:).