swift - 使用 VFL 添加约束 - iOS Swift

Question

我正在了解 VFL，并且正在尝试一些我需要帮助的东西。

我在纵向模式下将 ImageView 对齐，如下图所示。

横向 View 如下所示

在横向中，我希望图像沿 Y 轴居中，即比图像中显示的稍高一些。

我有以下 VFL 代码

override func viewDidLoad() {

    googleSignButton = UIImageView()
    googleSignButton!.translatesAutoresizingMaskIntoConstraints = false
    googleSignButton!.image = UIImage(named: "google.png")
    self.view!.addSubview(googleSignButton!)

    let buttonWidth:CGFloat = 50
    let views:[String:UIImageView] = Dictionary(dictionaryLiteral: ("google",googleSignButton!))
    let metrics = ["dim" : buttonWidth,
                       "horizontalPadding" : (UIScreen.mainScreen().bounds.width - (3 * buttonWidth)) / 3,
            "verticalPadding" : (UIScreen.mainScreen().bounds.height * 0.5) - (buttonWidth * 0.5)]

        let horizontalConstraint = NSLayoutConstraint.constraintsWithVisualFormat("H:|-horizontalPadding-[google(dim)]", options:[] , metrics: metrics, views: views)
        let verticalConstraint = NSLayoutConstraint.constraintsWithVisualFormat("V:|-verticalPadding-[google(dim)]", options:[] , metrics: metrics, views: views)
        self.view.addConstraints(verticalConstraint)
        self.view.addConstraints(horizontalConstraint)
}

我怎样才能做到这一点。肖像模式看起来不错，在横向模式下，图像必须垂直居中。

谢谢。

编辑

更新的代码:

override func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {

        super.viewWillTransitionToSize(size, withTransitionCoordinator: coordinator)

        coordinator.animateAlongsideTransition({ (UIViewControllerTransitionCoordinatorContext) -> Void in



            }) { (UIViewControllerTransitionCoordinatorContext) -> Void in

                self.calculateConstraints()

        }
    }

    func calculateConstraints() {

        let buttonWidth:CGFloat = Common.sharedCommon.calculateDimensionForDevice(50)

        let views:[String:UIImageView] = Dictionary(dictionaryLiteral: ("google",googleSignButton!))
        let metrics = ["dim" : 50.0,
            "horizontalPadding" : (UIScreen.mainScreen().bounds.width - (3 * buttonWidth)) / 3,
            "verticalPadding" : (UIScreen.mainScreen().bounds.height * 0.5) - (buttonWidth * 0.5)]


        if let horizontal = horizontalConstraint, let vertical = verticalConstraint {

            NSLayoutConstraint.deactivateConstraints([horizontal])
            NSLayoutConstraint.deactivateConstraints([vertical])
        }

        horizontalConstraint = NSLayoutConstraint.constraintsWithVisualFormat("H:|-horizontalPadding-[google(dim)]", options:[] , metrics: metrics, views: views)[0]
        verticalConstraint = NSLayoutConstraint.constraintsWithVisualFormat("V:|-verticalPadding-[google(dim)]", options:[] , metrics: metrics, views: views)[0]

        NSLayoutConstraint.activateConstraints([horizontalConstraint!,verticalConstraint!])

}

图片:

Answer 1

所以你的问题是约束不会在旋转时更新，因此它对景观使用相同的垂直约束。

首先，您实际上需要将约束保存在属性中以用于停用目的。在你的 View Controller 中:

var verticalConstraints: [NSLayoutConstraint]?
var horizontalConstraints: [NSLayoutConstraint]?

然后，将约束代码包装在一个函数中(注意我稍微修改了它):

function calculateButtonConstraints() {
    let buttonWidth:CGFloat = 50
    let views:[String:UIImageView] = Dictionary(dictionaryLiteral: ("google",googleSignButton!))
    let metrics = ["dim" : buttonWidth,
                   "horizontalPadding" : (UIScreen.mainScreen().bounds.width - (3 * buttonWidth)) / 3,
        "verticalPadding" : (UIScreen.mainScreen().bounds.height * 0.5) - (buttonWidth * 0.5)]

    if let horizontal = horizontalConstraints, let vertical = verticalConstraints {
        NSLayoutConstraint.deactivateConstraints(horizontal)
        NSLayoutConstraint.deactivateConstraints(vertical)
    }

    horizontalConstraints = NSLayoutConstraint.constraintsWithVisualFormat("H:|-horizontalPadding-[google(dim)]", options:[] , metrics: metrics, views: views)
    verticalConstraints = NSLayoutConstraint.constraintsWithVisualFormat("V:|-verticalPadding-[google(dim)]", options:[] , metrics: metrics, views: views)

    NSLayoutConstraint.activateConstraints(horizontalConstraints!)
    NSLayoutConstraint.activateConstraints(verticalConstraints!)
}

请注意，我使用了 NSLayoutConstraint.activateConstraints:，因为这是首选方式。此外，这也是 deactivateConstraints: 的一部分。

然后，将以下代码替换为 viewDidLoad: 中的代码:

calculateButtonConstraints()

接下来，将其添加到您的 View Controller :

override func viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {

    coordinator.animateAlongsideTransition(nil, completion: { [unowned self]
        self.calculateButtonConstraints()
    })

    super.viewWillTransitionToSize(size, withTransitionCoordinator: coordinator)

}