以编程方式更改集合视图约束

Question

I have create a collection view in my storyboard and add constraints. Now I need to change the collection view constraint for a specific condition and I want to do it programmatically in my class. I have an IBOutlet for the collection view. What parameter needs to be changed?

Answer 1

1. Add the constraints normally in the collection view
2. Select the constraint you want to modify, hold Control and drag to your class
3. When you want your constraint to be changed, type nameOfYourConstraint.constant = 100 // Int

Answer 2

First create IBOutlet of constraints required to changed by dragging to ViewController

The constant value needs to be cahnged, eg:

self.outlet.constant = 50

Don't forget to call self.view.layoutIfNeeded after modifying the constant.

Answer 3

您需要创建约束的IBOutlet，并根据您的条件更新约束值。

Answer 4

By using UICollectionViewFlowLayout,you can easily change the layout of collection view.

    let layout = UICollectionViewFlowLayout()
    collectionView.collectionViewLayout = layout
    layout.sectionInset = UIEdgeInsets(top:0, 
    left:0,bottom:0,right:0)
    let itemWidth:CGFloat = (UIScreen.main.bounds.width)/2
    layout.itemSize = CGSize(width: itemWidth, height: itemWidth)
    layout.minimumLineSpacing = 0
    layout.minimumInteritemSpacing = 0