如何以编程方式根据纵向/横向更改布局约束？ [复制]

Question

我以编程方式构建所有对象和标签，并有一个名为 setupLayout() 的函数，如下所示：

 private func setupLayout() {

//The Image that presents the Logo of the chosen cryptocurrency.
    view.addSubview(cryptoIconImage)
    cryptoIconImage.translatesAutoresizingMaskIntoConstraints = false
    cryptoIconImage.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    cryptoIconImage.topAnchor.constraint(equalTo: view.topAnchor, constant: 50).isActive = true
    cryptoIconImage.widthAnchor.constraint(equalToConstant: 60).isActive = true
    cryptoIconImage.heightAnchor.constraint(equalToConstant: 60).isActive = true


//The Label that presents the name of the chosen cryptocurrency.
    view.addSubview(cryptoLabel)
    cryptoLabel.translatesAutoresizingMaskIntoConstraints = false
    cryptoLabel.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    cryptoLabel.topAnchor.constraint(equalTo: cryptoIconImage.bottomAnchor, constant: 10).isActive = true
    cryptoLabel.font = customFont?.withSize(32)
}

这样可以保持布局美观且居中，适用于肖像，也适用于横向。问题是在横向时，我不希望元素居中，我想将一些元素移到屏幕的左侧，一些移到右侧（我没有在设置中显示所有项目）任何其他答案对这个问题似乎都使用故事板，我发现这种方法可以使用：

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {

    let orient = UIApplication.shared.statusBarOrientation
    print(orient)

    switch orient {
    case .portrait:
        print("Portrait")
        break
    // Do something
    default:
        print("LandScape")
        // Do something else
        self.landscapeLayout()
        break
    }
}

但我不确定我应该如何更改删除和添加新约束，以便在来回时顺利运行。我想过有一个横向布局函数（），例如：

    private func landscapeLayout() {
    view.addSubview(cryptoIconImage)
    cryptoIconImage.translatesAutoresizingMaskIntoConstraints = false
//Removing centerXAnchor
    cryptoIconImage.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = false
    cryptoIconImage.topAnchor.constraint(equalTo: view.topAnchor, constant: 50).isActive = true
    cryptoIconImage.widthAnchor.constraint(equalToConstant: 60).isActive = true
    cryptoIconImage.heightAnchor.constraint(equalToConstant: 60).isActive = true
//Putting it to the left side
    cryptoIconImage.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 30).isActive = true

}

但这给我带来了拉伸等问题，并且在添加新标签内容时摆脱了标签内容。我应该如何在纵向和横向之间设置 2 个单独的布局？

Answer 1

你可以这样做：

声明变量来保存约束。

var cryptoIconImageCenterXWhenPortrait : NSLayoutConstraint?
var cryptoIconImageCenterXWhenLandscape : NSLayoutConstraint?

定义两个约束

cryptoIconImageCenterXWhenPortrait = cryptoIconImage.centerX.constraint(equalTo: window.centerX)
cryptoIconImageCenterXWhenLandscape = cryptoIconImage.centerX.constraint(equalTo: window.centerX, constant: -20)

相应地激活它们

If Landscape {
   cryptoIconImageCenterXWhenPortrait.isActive = false
   cryptoIconImageCenterXWhenLandscape.isActive = true
} else If Portrait {
   cryptoIconImageCenterXWhenPortrait.isActive = true
   cryptoIconImageCenterXWhenLandscape.isActive = false
}