Switching quickly between UIPageController pages results in glitches and crash

Originator:me
Number:rdar://20302671 Date Originated:25-Mar-2015 05:54 PM
Status:Open Resolved:
Product:iOS SDK Product Version:iOS 8.3 (12F5047e)
Classification:Crash/Hang/Data Loss Reproducible:Always
 
Description:
Switching quickly between the pages of a UIPageController results in visual glitches (views disappearing and replaced with black), and eventually crashes. See attached sample project and video.


Steps to Reproduce:
Switch quickly between UIPageViewController’s pages via page control (or other UI mechanism).


Expected Results:
No crash; child view controllers visible when on-screen.


Actual results:
Views disappear and are replaced with black when still on-screen.
Assertion failure:
*** Assertion failure in -[_UIQueuingScrollView _enqueueCompletionState:], /SourceCache/UIKit_Sim/UIKit-3347.28.1/_UIQueuingScrollView.m:499
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Duplicate states in queue'


Configuration:
iPhone 5 Simulator, 7.1, 8.1, 8.3


Attachments:
http://www.mediafire.com/watch/884cenqkl7a9w93/UIPageViewController_Bug.mov
http://www.mediafire.com/download/4ev9nall2dc9565/PageBugDemo.zip

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