UICollectionView Frame Wrong With Toolbar - iphone

Question

I have a UICollectionViewController that is part of a Navigation Controller and Tab Bar Controller. At the beginning of the Navigation Controller, I have Interface Builder set to display the Toolbar at the bottom of the View. For the first View Controller of the Navigation Controller, I am using [self.navigationController setToolbarHidden:YES animated:YES]; in order to hide the Toolbar, then in my UICollectionViewController, I use
-(void)viewWillAppear:(BOOL)animated
{
[self.navigationController setToolbarHidden:NO animated:YES];
}
in order to have the Toolbar be displayed. This part works perfectly, my problem comes from the UICollectionViewCell that I have in the UICollectionView. I want it to be the full size of the UICollectionView, and I'm using AutoLayout, so I'm using:
-(CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
return self.collectionView.frame.size;
}
However, the first time the view is loaded, it returns the wrong value. The first time the view and CollectionView are loaded, that returns the size of the collectionView INCLUDING the height of the Toolbar, which then leads to the warning:
the item height must be less that the height of the UICollectionView
minus the section insets top and bottom values.
And the cell doesn't load. However, when I force a [self.collectionView reloadData]; after the warning, the correct value is returned for self.collectionView.frame.size and the cell loads.
I'm really frustrated at this and would greatly appreciate any help that anyone can offer.
Edit:
After reading Mundi's comment, I ended up changing some of my code to:
-(void)viewWillAppear:(BOOL)animated
{
[self.navigationController setToolbarHidden:NO animated:YES];
[self.collectionView reloadData];
}
And the issue was solved. However, now I have a new but related problem. When I add [self.collectionView scrollToItemAtIndexPath:selectedIndexPath atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally animated:NO]; (selectedIndexPath is pushed from the first view controller) to viewWillAppear, I get the same warning about the size of the UICollectionView item. If I have my code like this:
-(void)viewWillAppear:(BOOL)animated
{
[self.navigationController setToolbarHidden:NO animated:YES];
[self.collectionView scrollToItemAtIndexPath:selectedIndexPath atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally animated:NO];
[self.collectionView reloadData];
}
I don't get that size warning, but my collectionView always starts at index 0 rather than selectedIndexPath. If I change around the ordering to this:
-(void)viewWillAppear:(BOOL)animated
{
[self.navigationController setToolbarHidden:NO animated:YES];
[self.collectionView reloadData];
[self.collectionView scrollToItemAtIndexPath:selectedIndexPath atScrollPosition:UICollectionViewScrollPositionCenteredHorizontally animated:NO];
}
I get that size warning, and the cell doesn't load until I invoke a method to call reloadData. However, it does start at the correct indexPath.

Answer 1

This problem is really about dealing with the view lifecycle. In viewWillAppear all the subviews are already laid out, so maybe you are hiding the toolbar too late.
Your solution to call reloadData after showing the toolbar is not so bad as all this happens before the view appears. It is logical - the geometry has changed and you have to recalculate the layout.
Try experimenting with the view controller's hidesBottomBarWhenPushed property. Maybe that takes care of this problem without having to code anything.