Race Condition when loading media and changing the view size

[pavol-bielik]

Description

It is possible to change the view size of media while they are loading in the background.
As a result the medias can be temporary shown in the wrong order.

Steps to reproduce the issue

Initial state: main activity showing the listing of medias by folder is shown and view size is set to medium

1. click on option at top of the screen and change the group by to Date. As a result a background task is created that first loads the medias and sorts them based on the selected grouping.
2. while the medias are loading, change the view size to small. The application takes currently shown medias and immediately redraws them with the new view size. However, it already accounts for the changed grouping option and takes the old medias (ordered by folder) and groups them by date. As a result they are very likely to be in the wrong order.
   
3. The background task created in step 1. finishes and redraws the medias in the correct order.
   

The wrong execution can be easily triggered after adding Thread.sleep to simulate slow database before Utils.loadMedia(false) call.

Possible Fix

We can make the two events (changing the view size and loading) commutative by always resorting the current medias when the view size changes.

[rafali]

Thanks for the detailed bug report. I'll fix it.

[rafali]

Solved using @Background(serial = "load")