SubView约束

Question

我似乎不能弄清楚，当我在模拟器中构建应用程序时，我的左/右UIEdgeInsets没有影响。除了这个问题，我希望我的UICollectionView单元格在一行中有3个项目，但我得到的所有单元格都是彼此整齐的，而且它们非常长。我哪里错了？

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: view.frame.width, height: 100)
    }

Answer 1

在代码中，

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: view.frame.width, height: 100)  >>>> You are applying parent view width(full width) to item width
}

将以下代码添加到sizeForItemAt方法以获得所需的输出

//define constant value as per your requirement and declare this variables globally
let inset: CGFloat = 10 //define as per your requirement
let minimumInteritemSpacing: CGFloat = 10 //define as per your requirement
let cellsPerRow = 3

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        
   let marginsAndInsets = inset * 2 + collectionView.safeAreaInsets.left + collectionView.safeAreaInsets.right + minimumInteritemSpacing * CGFloat(cellsPerRow - 1)
        
   let itemWidth = ((collectionView.bounds.size.width - marginsAndInsets) / CGFloat(cellsPerRow)).rounded(.down)
   
   return .init(width: itemWidth, height: itemWidth)
        
}

Answer 2

您可以像这样按行函数显示三个单元格

 let spaceBetweenCells: CGFloat = 10
 collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize(width: (collectionView.frame.width - 2* spaceBetweenCells)/3, height: 100)
    }