AutoLayout 不以编程方式更新视图 - Swift

Question

我有以下代码，我在其中创建和布置代码中的所有内容。我想要做的是在点击按钮时修改 myTopContainer 但我无法更改宽度，只能修改高度。

知道为什么吗？

func setupAutoLayout(){
    NSLayoutConstraint.activate([
        // My Container
        myTopContainer.bottomAnchor.constraint(equalTo: myButton.topAnchor, constant: -5),
        myTopContainer.heightAnchor.constraint(equalToConstant: 50),
        myTopContainer.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 15),
        myTopContainer.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -15),

        // My Button
        myButton.widthAnchor.constraint(equalToConstant: 80),
        myButton.heightAnchor.constraint(equalToConstant: 40),
        myButton.trailingAnchor.constraint(equalTo: self.view.trailingAnchor, constant: -15),
        myButton.bottomAnchor.constraint(equalTo: self.view.bottomAnchor, constant: -400)
    ])
}


@IBAction func relayoutViews(_ sender: Any) {

    UIView.animate(withDuration: 0.5, delay: 0, options: .curveEaseIn, animations: {

        self.myTopContainer.heightAnchor.constraint(equalToConstant: 50).isActive = false
        self.myTopContainer.leadingAnchor.constraint(equalTo: self.view.leadingAnchor, constant: 15).isActive = false

        // this is working, it changes the height
        self.myTopContainer.heightAnchor.constraint(equalToConstant: 10).isActive = true
        // this is not doing anything
        self.myTopContainer.leadingAnchor.constraint(equalTo: self.myButton.trailingAnchor).isActive = true

        self.view.layoutIfNeeded()

    })
}

Answer 1

像这样的一行

self.myTopContainer.heightAnchor.constraint(equalToConstant: 50).isActive = false

每次都创建一个新的约束。它不会修改之前创建的约束。

当您设置自动布局时，您应该在实际调用 NSLayoutConstraint.activate() 之前保存对您稍后要修改的约束的引用。稍后您可以将它们的 isActive 设置为 false。

例如：

var someConstraint: NSLayoutConstraint?
func setupAutoLayout(){
    let aConstraint = myTopContainer.bottomAnchor.constraint(equalTo: myButton.topAnchor, constant: -5)
    someConstraint = aConstraint
    NSLayoutConstraint.activate([
        // My Container
        aConstraint
    ])
}

func editConstraint() {
    self.someConstraint?.isActive = false
}

无论如何，当你编辑约束时要小心日志，你可能会在编辑时破坏某些东西。如果您看到那些破坏约束的日志，则意味着仍然有问题（即使它在视觉上看起来不错，它也可能在其他情况下崩溃或无法正常工作）

AutoLayout 不以编程方式更新视图 - Swift

AutoLayout not updating views programmatically - Swift

ios

autolayout

swift