How do I define the size of a CollectionView on rotate

Question

I have a viewcontroller with 2 CollectionView Controllers.

I would like on rotation that only one of the collection views resize to a custom size while the other re

Answer 1

I've solved this problem by checking the rotation of the device and then reloading the layout. Checking the screen size and using this size to display my cell.

- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation
{
    //get new width of the screen
    screenRect = [[UIScreen mainScreen] bounds];
    screenWidth = screenRect.size.width;

    //if landscape mode
    if (UIDeviceOrientationIsLandscape([UIDevice currentDevice].orientation))
    {
        screenDivide = 5;
    }
    else
    {
        screenDivide = 3;
    }

    //reload the collectionview layout after rotating
    UICollectionViewFlowLayout *layout = (UICollectionViewFlowLayout *)self.collectionView.collectionViewLayout;
    [layout invalidateLayout];
}

Then I defined the cells like this

- (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
    screenRect = [[UIScreen mainScreen] bounds];
    screenWidth = screenRect.size.width;

    CGSize elementSize = CGSizeMake(screenWidth/screenDivide, 100);
    return elementSize;
}