A few weeks back I ran into an interesting UITableView bug and I finally got around to writing up a test case and submitted a Radar to Apple. The test application source is on my GitHub and I've copied the radar to Open Radar.

I'm working on an app right now that has the option of driving a second screen. There are two methods of connecting such a screen: using a special dock cable to physically connect a monitor; and using Airplay to connect to an Apple TV device and using that screen.

Note that I'm not talking about mirroring the iPad display to the second display, I'm talking about having a completely different UIView on the second display. (This is confusing because iOS calls turning that on "Airplay Mirroring" although it's entirely up to the application whether it actually mirrors the main view or not.)

This second display is primarily a UITableView and it can potentially have quite a few rows to display. Also the intent is to have a screen that can be read at a distance so I use quite a large font (the current "large" size font is 36 point.) Since there's no touch UI there's no way for the user to directly scroll the secondary display but the app scrolls the second display to match a similar table on the iPad display. As the user manipulates the main display the secondary screen scrolls in unison. Well, at least it should and that right there is the bug. In my experience any UITableView method call that takes an animated: parameter does not animate on the Airplay secondary screen if animated: is set to YES. This works fine on the physical secondary screen, but not the Airplay. For example scrollToRowAtIndexPath:atScrollPosition:animated: will silently fail if you try to animate it.

There's also a workaround I have, and you can see it in the code on GitHub. Short form is this: animating the contentOffset value of the table in a GCD block via [UIView animateWithDuration:delay:options:animations:completion] works. So instead of simply scrolling to a row, I calculate a contentOffset for that row and scroll the underlying UIScrollView.

I was not able to find any references to this bug anywhere via Google so I'm not sure it's been reported before. If you want to animate a UITableView on an Airplay secondary screen you probably want to take a look at the GitHub repository.