Change scroll direction in UICollectionView

Question

I have a UICollectionView which I have setup, everything works fine (selection, headers, etc), however, I want to change the scroll direction in some situations.

In short if I go into the story board and change the scrollDirection it works fine but I want to do it programatically!

I have tried to change the scroll direction of the collection view directly with something like

    [myCollectionView setScrollDirection:....and so on.......

But this does not work, I can not find scrollDirection or similar in there.

I have also tried to setup a flow layout but I am sure i am doing this wrong (i.e. trying to set a ViewLayout to a FlowLayout).

    UICollectionViewFlowLayout *flowLayout = [[UICollectionViewFlowLayout alloc]init];
    [flowLayout setScrollDirection:UICollectionViewScrollDirectionVertical];
    [myCollectionView setCollectionViewLayout:flowLayout];

This crashes with a lot of Constraint problems and I suspect I need to do a lot more work with the flowLayout (from what I have found it is a bit above me right now).

It should also be noted that I am using a custom cell, headers and footers.

In short is there an easy way to do this or not? OR does anyone know a good Flow Layout tutorial?

EDIT

I setup the collection view as such;

[myCollectionView setDataSource:self];
[myCollectionView setDelegate:self];

I implement these delegate methods and all work fine

viewForSupplementaryElementOfKind
numberOfSectionsInCollectionView
numberOfItemsInSection
cellForItemAtIndexPath
didSelectItemAtIndexPath

I have added the DataSource and Delegate to the .h and also the FlowLayout delegate BUT I am not sure what I should also have for the latter.

Most of the visual layout is done in Story Board, there are a few things such as Font, size and colour which I do programatically.

ANOTHER EDIT

This is the error when I try to change the FlowLayout, I also get this when I try and invalidate the layout.

Unable to simultaneously satisfy constraints. Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)

"<NSAutoresizingMaskLayoutConstraint:0x89967f0 h=--& v=--& V:[menuCell:0x8991700(50)]>",
"<NSLayoutConstraint:0x8991200 menuCell:0x8991700.bottom == UILabel:0x8992be0.bottom + 100>",
"<NSLayoutConstraint:0x898fd50 UILabel:0x8992be0.top == menuCell:0x8991700.top + 3>"

Will attempt to recover by breaking constraint

Break on objc_exception_throw to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in may also be helpful.

Answer 1

Ok, try calling invalidateLayout on your collection view like so:

[myCollectionView.collectionViewLayout invalidateLayout];

This forces the collection view to update its layout at that point (See apple documentation here). I'm not certain, but I don't imagine this is called when you change the scroll direction.

See if that gets you anywhere near!

Answer 2

do this:

- (IBAction)changeDirection:(UIButton *)sender
{
     UICollectionViewFlowLayout *layout = (UICollectionViewFlowLayout *)[self.collectionView collectionViewLayout];
     if(layout.scrollDirection == UICollectionViewScrollDirectionHorizontal)
     {
        layout.scrollDirection = UICollectionViewScrollDirectionVertical;
     }
     else
     {
         layout.scrollDirection = UICollectionViewScrollDirectionHorizontal;
     }
}

It works for me.

Answer 3

In swift you can do this:

//From the collection view subclass
    if let layout: UICollectionViewFlowLayout = self.collectionViewLayout as? UICollectionViewFlowLayout {
        layout.scrollDirection = .Vertical
    }

Answer 4

You can do it with property observer didSet{} with your collection view outlet.

Assuming that the outlet for the collectionView is myCollectionView, in the code add a didSet property observer to the outlet and change the layout's direction. Something like-

@IBOutlet weak var myCollectionView:UICollectionView!{
      didSet{
            let layout = contentCollectionView.collectionViewLayout as!
UICollectionViewFlowLayout
            layout.scrollDirection = .Vertical
        }
}

Normally a collectionView is dropped in storyboard from object library, it automatically comes with FlowLayout. You can change this layout's flow direction by telling your code that when I get my collection view, I want its layout's scroll direction to be horizontal or vertical.