CollectionView 约束打破

Question

I have a collectionView and each cell contains a tableView inside it. The gray portion is supposed to be the collectionView.

But when I run the app, I get something like this

As you can clearly see that the table view present doesn't stick to the constraints set. I get the following errors from the console.

The behavior of the UICollectionViewFlowLayout is not defined because:
the item height must be less than the height of the UICollectionView minus the section insets top and

bottom values, minus the content insets top and bottom values.
The relevant UICollectionViewFlowLayout instance is <UICollectionViewFlowLayout: 0x7f80fd28e420>, and it 

is attached to <UICollectionView: 0x7f80fc08f800; frame = (0 114; 375 664); clipsToBounds = YES;
autoresize = RM+BM; gestureRecognizers = <NSArray: 0x600000d6c4b0>; layer = <CALayer: 0x6000003beee0>;
contentOffset: {0, 0}; contentSize: {0, 0}; adjustedContentInset: {0, 0, 0, 0};

layout: <UICollectionViewFlowLayout: 0x7f80fd28e420>; dataSource: <BizTiz.EventDetailController: 0x7f80fa0b7800>>.

Make a symbolic breakpoint at UICollectionViewFlowLayoutBreakForInvalidSizes to catch this in the debugger.

How do I fix this? Also when I push this collectionView onto the stack, there is a small lag. I am guessing this might be due to the previous error.

Answer 1

Please set layout in the UICollectionViewDelegateFlowLayout.

   func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: <cell_width>, height: <cell_height>)
    }

Answer 2

Realized my mistake....

   func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: view.frame.width, height: view.frame.height - 114)
    }

I was setting the height as view.frame.height . I had forgotten to subtract the extra height at top.