如何將視圖高度設置為等於其寬度

Question

我創建了一個UIView，然后我在uiview上添加了一個約束，它的寬度等於它的superview寬度。 然后我想讓這個uiview的高度等於它的寬度。 我不知道如何添加這種約束。 我可以看到我可以在此視圖上添加高度約束，但如何將其值設置為等於其寬度？

Answer 1

將Aspect Ratio約束添加到視圖中

Answer 2

嘗試這個：

yourView.translatesAutoresizingMaskIntoConstraints = false
yourView.addConstraint(NSLayoutConstraint(item: yourView, attribute: .Height, relatedBy: .Equal, toItem: yourView, attribute: .Equal, multiplier: 1, constant: yourWidthHere))

或者，您可以將Width Constraint和Height Constraint的IBOutlet拖到ViewController：

@IBOutlet weak var heightConstraint: NSLayoutConstraint!
@IBOutlet weak var widthConstraint: NSLayoutConstraint!

並將高度設置為寬度：

heightConstraint.constant = widthConstraint.constant

Answer 3

您可以從storyboard或以programmatically將視圖高度設置為等於其寬度，因此您需要在具有乘數1的視圖上添加aspect ratio約束。

在故事板中，您可以在故事板中借助Pin Tools添加aspect ratio約束

通過編程方式，您可以嘗試下面的代碼，它工作正常。

override func viewDidLoad() {
    super.viewDidLoad()

    let myView = UIView()
    myView.backgroundColor = UIColor.redColor()
    self.view.addSubview(myView)
    myView.translatesAutoresizingMaskIntoConstraints = false

    // here I'm setting the CenterX & CenterY constraint equal to its superview CenterX & CenterY
    view.addConstraint(NSLayoutConstraint(item: myView, attribute: .CenterX, relatedBy: .Equal, toItem: view, attribute: .CenterX, multiplier: 1, constant: 0))
    view.addConstraint(NSLayoutConstraint(item: myView, attribute: .CenterY, relatedBy: .Equal, toItem: view, attribute: .CenterY, multiplier: 1, constant: 0))

    // here I'm setting the width constraint equal to its superview width
    view.addConstraint(NSLayoutConstraint(item: myView, attribute: .Width, relatedBy: .Equal, toItem: view, attribute: .Width, multiplier: 1, constant: 0))

    // here I'm setting the aspect ratio constraint to equal width or height of myView
    // since  aspect ratio constraint belongs to self width or height so add this constraints it self(i.e. myView) but not in its superView
    myView.addConstraint(NSLayoutConstraint(item : myView, attribute: .Width, relatedBy: .Equal, toItem: myView, attribute: .Height, multiplier: 1, constant: 0))
}