Re: Collection Views Breaking
Re: Collection Views Breaking
- Subject: Re: Collection Views Breaking
- From: Alex Zavatone <email@hidden>
- Date: Wed, 20 May 2015 14:12:18 -0400
Whaaa?
The app throws an exception, but setting an exception breakpoint never gets triggered?
Anyway, you may find these helpful.
http://loufranco.com/blog/understanding-exc_bad_access
http://www.touch-code-magazine.com/how-to-debug-exc_bad_access/
Enabling NSZombies may help you track that down, Carl.
Good luck
On May 20, 2015, at 1:39 PM, Luther Baker wrote:
> Thanks Alex,
>
> I have set an exception breakpoint but it never fires - and I will experiment with popping the second view controller programmatically and scrolling up.
>
> I think this has to do with my elementary understanding of how UICollectionViews are reused in this type of transition animation - I've learned, for instance, that the datasource isn't actually changing (as part of "useLayoutToLayoutNavigationTransitions").
>
> A tangental point I'm better understanding is that this property really just causes collection view controller push transitions to use the 'pushed' controller's layout ... (ie: the datasource is ignored).
>
> For example, tapping on a particular picture in a grid and pushing a new collection view controller on the stack might not actually change the existing picture data but does potentially reflow the layout - like, could make the selected picture huge. Yes, I am thinking that is probably the purpose of setting this particular property.
>
> Thanks again for looking and replying!
> -Luther
>
>
>
> On Wed, May 20, 2015 at 11:42 AM, Alex Zavatone <email@hidden> wrote:
> What if you issue the back programatically and then scroll up?
>
> It would be interesting to see just what gets unwired here.
>
> Have you set an exception breakpoint to tell you exactly what is breaking?
>
> On May 20, 2015, at 12:46 AM, Luther Baker wrote:
>
> > I've got a simple iOS project consisting of 2 collection view controllers
> > and a navigation controller.
> >
> > Tapping any item in the first collection view simply pushes the second
> > collection view on the stack.
> >
> > Problem is, when I tap "< Back" and then manually scroll up ... the app
> > crashes with a EXC_BAD_ACCESS error in main.
> >
> > Nothing is logged ... and the stack in the thread looks something like
> >
> > 0 objc_msgSend
> > 16 UIApplicationMain
> > 17 main
> > 18 start
> > 19 start
> >
> > with 17 main highlighted.
> >
> > /////
> >
> > In the code, FirstViewController and SecondViewController are almost
> > identical save for one line. I am specifically looking at what line 24 in
> > SecondViewController does to the push transition.
> >
> > self.useLayoutToLayoutNavigationTransitions = YES;
> >
> > Upon running, the collection view "push" animation looks fine - and the "<
> > Back" button actually works ... but once I get back to FirstViewController,
> > the original colors never come back. In addition, when I scroll up, I get
> > the error listed above.
> >
> > I've thrown together a small project to demonstrate:
> > https://github.com/LutherBaker/CollectionViewDemo
> >
> > Thoughts? It feels like I'm not referencing something I should be ...
> >
> > Thanks,
> > -Luther
> >
> > PS: I think you may ignore this but note that when you initially select an
> > item in the FirstViewController and "push" - the console spits lots and
> > lots of
> >
> > *Snapshotting a view that has not been rendered results in an empty
> > snapshot. Ensure your view has been rendered at least once before
> > snapshotting or snapshot after screen updates.*
> > which I assume is simply a bug or non-relevant logging accidentally left in
> > the framework.
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