swift - 更改 View 宽度约束

Question

我这样设置 UIView 的宽度:

contentView.widthAnchor.constraint(equalToConstant: CGFloat(scrollWidth())).isActive = true

现在我想改变那个宽度。问题是:如何删除旧约束并添加新约束？我确实像这样创建了 NSLayoutConstraint

scrollWidthConstraint = NSLayoutConstraint(
    item: contentView,
    attribute: .width,
    relatedBy: .equal,
    toItem: nil,
    attribute: .notAnAttribute,
    multiplier: 1.0,
    constant: CGFloat(scrollWidth())
)

如何为 UIView 设置约束以供以后更改？

Answer 1

首先更好更简短地使用它并为其分配一个引用

var widCon:NSLayoutConstraint! 

widCon = contentView.widthAnchor.constraint(equalToConstant: CGFloat(scrollWidth()))
widCon.isActive = true

而不是 NSLayoutConstraint(item: contentView, 然后更改它的常量

widCon.constant = ////