Custom cell width for one collectionView

Question

I have 3 collectionViews in one view controller. One has all cells of the same width and does not change. The other I would like to set the cell width in code using a constant. The last will calculate its cell's width based on the previous constant and other factors in a custom flow layout.

I tried

extension YourViewController: UICollectionViewDelegate,UICollectionViewDataSource,UICollectionViewDelegateFlowLayout {



      func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
             if collectionView == neededCollectionView {
             return CGSize(width: constantWidth, height: constHeight)
             } else {
                // here ignore all the others and tell them to get this size as usual
             }
        }

    }

but this seems to modify the width for all the collection views .. How do I get this two ignore the 2 collection views that have their size calculated somewhere else

Answer 1

在此功能中，您不能忽略， 您需要返回

  

CGSize

总是。

尝试一个断点，并检查是否进入else闭包 您可以尝试添加此行，

 return CGSize(width: yourDefualtWidthConst, height:yourDefualtHeightconst)

或此

 return collectionView.itemSize 

Answer 2

您有两个选择

  

第一选项：返回每个CollectionViewCell的EstimatedItemSize

1。。从每个CollectionViewFlowLayout获取IBOutlet参考。

@IBOutlet weak var firstFlowLayout: UICollectionViewFlowLayout!

2。。在您的viewController中添加UICollectionViewDelegateFlowLayout委托

3。。实现委托方法

func collectionView( _ collectionView: UICollectionView,layoutcollectionViewLayout: UICollectionViewLayout,sizeForItemAtindexPath: IndexPath) -> CGSize {

         if collectionView.tag == 1 {
         return CGSize(width: constantWidth, height: constHeight)
         } elseIf collectionView.tag == 2 {
         return firstFlowLayout.estimatedItemSize
         }
}

  

第二个选择：Adepter设计模式

您还可以为每个collectionview使用适配器类，并且每个适配器都有不同的实现来解决此问题

https://stackoverflow.com/a/50920915/5233180

否：对于TableView的此实现，您可以将其用于collectionview