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At a great number of requests from people using older iOS hardware, I'm currently refactoring and optimizing my app so it will work on iOS 3. That being said I've got a glitch with my UITabBar that I can replicate on all of the iPhone 3G units I've tested it on.

The glitch appears to have been fixed in iOS 4, but I was wondering if before that time, anyone else had this glitch as well and had figured out a (relatively elegant) workaround for it.

The problem is what you can see below; when a memory warning occurs and all of the views offscreen are released, when I bring a view controller with a tab bar back on screen, all of the UITabBarItems that are supposed to be in it are gone. As far as I can see, they're not being drawn at all; ie tapping the tab bar has no effect. After setting breakpoints and examining the UITabBar and its items in memory, they're all still there (ie not getting released), just that they're not getting redrawn when the UITabBar is re-created in the controller loadView method.

My app works similar to the official Twitter app in that I implemented my own version of UITabBarController so I could control the integration of it with a parent UINavigationController properly. I set it up as closely as possible to the original UITabBarController class though, with all of the child view controllers handling their own respective UITabBarItems and initializing them inside the class' init methods. Once the child view controllers are passed to my TabController object via an accessor method, the tabBarItems are accessed and added to the UITabBar view.

Has anyone seen this behaviour before and know of a way I can fix it? I'm hoping there's a really simple fix for this since it already works in iOS 4, so I don't want to hack it up too badly.

Thanks a lot!

Home Screen after memory warning has occurred

TiM
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1 Answers1

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After a bit of research, I think I found a solution to this. It's not the most elegant solution I was after, but it definitely works.

I'm guessing after a memory warning is triggered, something is happening to the UITabBarItem objects that basically renders them corrupt. I tried a lot of things (flushing out the UITabBar, re-creating the controllers array etc), but nothing worked.

I finally discovered that if you completely destroy the UITabBarItems and allocate new ones in their place, then those ones will work. :)

So my final solution to this was to add an extra condition in the viewDidLoad method of my controller that if the detected system was iOS 3, and there was already an array of UITabBarItems, it would go through each one, copy out all of the properties needed, destroy it, allocate a new one and then copy the old properties over to the new one.

I'm still going to keep an eye out for a better solution (I think there's a bit of overhead in this method), but thankfully at this stage, iOS 3 legacy support is becoming less and less of an issue. :)

TiM
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  • That sounds good! Of course I'm more interested in your app, now that I see a screenshot. :) Link available? – Joe D'Andrea Oct 11 '11 at 22:09
  • Haha thanks! Ahhh, there was a link. But unfortunately, I got asked to take the app down. ^_^; (http://www.tim-oliver.com/2011/07/21/on-ipokedex-getting-pulled/) For the record, this is the last time I'm making my apps iOS 3 compliant. It's weird quirks like this that make it a crazy nightmare... – TiM Feb 04 '12 at 06:24
  • iOS 3? Yes, buh-bye. Let's hear it for Xcode 4.2, ARC, and Storyboards - mwahaaa. :) – Joe D'Andrea Feb 20 '12 at 21:50
  • As for the app takedown request, understood. (Side note: I also approached TPCi about an app before embarking upon it, and also did not proceed for similar reasons!) – Joe D'Andrea Feb 20 '12 at 21:59