swift - 使用函数停用 viewdidload 中声明的 nslayoutconstraint

Question

下面的代码在 viewdidload 中声明布局约束。当调用函数 Selena 时，我希望将约束更改为函数 selena 中的内容。当我调用该函数时，对象不会改变。它没有任何作用。我知道我必须以某种方式取消原来的限制。

   override func viewDidLoad() {

    NSLayoutConstraint.activate ([
        i.trailingAnchor.constraint(equalTo: view.centerXAnchor, constant :150),
        i.topAnchor.constraint(equalTo: view.centerYAnchor, constant : -200),

        i.widthAnchor.constraint(equalToConstant: 300),
        i.heightAnchor.constraint(equalToConstant: 450),

    ])

}


@objc func selena(){
    NSLayoutConstraint.activate ([
        i.trailingAnchor.constraint(equalTo: view.centerXAnchor, constant :50),
        i.topAnchor.constraint(equalTo: view.centerYAnchor, constant : -50),

        i.widthAnchor.constraint(equalToConstant: 20),
        i.heightAnchor.constraint(equalToConstant: 450),

    ])

}

Answer 1

您可以保留对它们的引用，然后使用停用

  var oldCons = [NSLayoutConstraint]()

   override func viewDidLoad() {
       super.viewDidLoad()
     oldCons = [
        i.trailingAnchor.constraint(equalTo: view.centerXAnchor, constant :150),
        i.topAnchor.constraint(equalTo: view.centerYAnchor, constant : -200), 
        i.widthAnchor.constraint(equalToConstant: 300),
        i.heightAnchor.constraint(equalToConstant: 450)
     ]
    NSLayoutConstraint.activate(oldCons)

}


@objc func selena(){

    NSLayoutConstraint.deactivate(oldCons)
    NSLayoutConstraint.activate ([
        i.trailingAnchor.constraint(equalTo: view.centerXAnchor, constant :50),
        i.topAnchor.constraint(equalTo: view.centerYAnchor, constant : -50), 
        i.widthAnchor.constraint(equalToConstant: 20),
        i.heightAnchor.constraint(equalToConstant: 450) 
    ])


}

<小时/>

高度约束没有改变，你可以从viewDidLoad内的数组中获取它

 i.heightAnchor.constraint(equalToConstant: 450).isActive = true

并将其从 selena 函数中删除