Changing orientation in paged mode about gmgridview

[steipete]

How exactly are they misaligned? Can you provide screenshots?

Start example, choose paging strategy layout, swipe to page other than 1st or last, rotate device and gridview will display space somewhere in a middle between two pages, and not automatically scroll to beginning of page.

[gmoledina]

Yup I'm able to reproduce it. Will be fixed soon.

[kylefox]

I think I'm experiencing the same issue (see screenshot). Any updates on this issue? Thanks!

[gmoledina]

Next in my list !

Out of curiosity, what's this app? Already in the appStore?

[kylefox]

Awesome, thanks! Let me know if there's anything I can do to help (although I'm quite a newb with iOS).

(The app isn't released yet, but I'll definitely tell you more about it once it is!)

[tonyarnold]

@gmoledina how'd you go with this error? I'm seeing it while using the development branch on an iPhone app.

[LauterAlsDerRest]

I fixed the issue for myself by implementing

• (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
  CGFloat pageWidth = _scrollView.frame.size.width;
  currentPage = floor((_scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
  }

in GMGridview

and doing
CGRect frame = _scrollView.frame;
frame.origin.x = frame.size.width * currentPage;
frame.origin.y = 0;
[_scrollView scrollRectToVisible:frame animated:NO];

at the end of - (void)relayoutItemsAnimated:(BOOL)animated in GMGridview

more of a bandaid-fix but it works.

[tonyarnold]

I'll give you an easier answer:

- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration
{
    [[self imageScrollView] willRotateToInterfaceOrientation:toInterfaceOrientation duration:duration];
    [super willRotateToInterfaceOrientation:toInterfaceOrientation duration:duration];
}

- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration
{
    [[self imageScrollView] willAnimateRotationToInterfaceOrientation:toInterfaceOrientation duration:duration];
    [super willAnimateRotationToInterfaceOrientation:toInterfaceOrientation duration:duration];
}

Add that to your view controller (where [self imageScrollView] is your GMGridView instance.

[kylefox]

@tonyarnold I'm a bit confused, how does that work? GMGridView doesn't seem to implement those selectors.

[LauterAlsDerRest]

@kylefox asked myself the same question. All I can say is that my bandaid-fix works, but it would be better to only reupdate after a rotation and only when in horizontal-paging-mode for performance reasons. Maybe I will handle this, but at the moment it just works as it is for me.

[kylefox]

@LauterAlsDerRest Interesting, I couldn't get your fix working either. Neither _scrollView nor currentPage existed. Are you using the master or develop brach?

[LauterAlsDerRest]

@kylefox you have to add and track the currentPage as a property for yourself, sorry for not being clear. _scrollView is/was a property for the underlying scrollview in the master-branch.

[tonyarnold]

@kylefox I'm working with the development branch. Perhaps these delegate methods have not made it into master yet.

[kylefox]

@LauterAlsDerRest Great, thanks for clarifying.

@tonyarnold Weird, I'm using the development branch as well. Aren't those methods located on UIViewController, rather than UIScrollView (from which GMGridView inherits)? When I try this with the latest code from the develop branch Xcode tells me:

No visible @interface for 'GMGridView' declares the selector 'willRotateToInterfaceOrientation:duration:'

[tonyarnold]

Completely my bad — you're correct. I was thinking about some other code, and somehow got it mixed up with GMGridView. Ignore me and go back to your lives… hands head in shame

[kylefox]

@tonyarnold Drat! I hoped I was just overlooking something ;)

@gmoledina Any updates / suggestions for how to tackle this issue? I've been hacking on the GMGridView but cannot seem to find the source of this bug. Probably because of my newness to iOS :)

Any clues would be greatly appreciated, I really want to squash this issue!

[kylefox]

For anyone else experiencing this issue, here's how you can patch it in your UIViewController:

-(void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
    CGPoint offset = CGPointMake(_currentPage * self.view.frame.size.height, 0);    
    [UIView
     animateWithDuration:duration
     animations:^{
         self.gridView.contentOffset = offset;
     }
     completion:nil];
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    CGFloat pageWidth = scrollView.frame.size.width;
    _currentPage = floor((scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
}

[scompt]

@kylefox's solution didn't work for me, so I came up with my own, also based on the develop branch:

- (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
    id<GMGridViewLayoutStrategy> layoutStrategy = gridView.layoutStrategy;
    if([layoutStrategy isKindOfClass:[GMGridViewLayoutHorizontalPagedStrategy class]]) {
        GMGridViewLayoutHorizontalPagedStrategy *pagedStrategy = layoutStrategy;
        if(pagedStrategy.numberOfItemsPerPage != 0) {
            [gridView scrollToObjectAtIndex:_currentPage * pagedStrategy.numberOfItemsPerPage atScrollPosition:GMGridViewScrollPositionNone animated:YES];
        }
    }
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    CGFloat pageWidth = scrollView.frame.size.width;
    _currentPage = floor((scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
}

It's less than ideal because there's a bit of a jerk at the beginning of the rotation. View the rotation in the simulator with slow-motion animations and you'll see what I mean.

[gmoledina]

It's now fixed in the master branch.
Thank you all for sharing all the code !