ios - 自动布局未正确设置 ImageView 框架

Question

只需将此图像放入 ImageView 中并设置为宽高比即可。

override func viewDidLoad() {
        super.viewDidLoad()
        let image = UIImage(named: "1-landscape")
        let imageView = UIImageView(image: image)
        imageView.translatesAutoresizingMaskIntoConstraints = false
        imageView.backgroundColor = UIColor.blackColor()
        imageView.contentMode = .ScaleAspectFit
        view.addSubview(imageView)
        var collector = [NSLayoutConstraint]()
        collector.appendContentsOf(NSLayoutConstraint.constraintsWithVisualFormat("H:|-0-[imageView]-0-|", options: [], metrics: nil, views: ["imageView": imageView]))
        collector.append(NSLayoutConstraint(item: imageView, attribute: .CenterY, relatedBy: .Equal, toItem: view, attribute: .CenterY, multiplier: 1, constant: 0))
        view.addConstraints(collector)
    }

运行时， View 的高度比图像的高度大 50%。为什么？？？

如果我们用老派的方式来表达我们的观点，是没有问题的。我是否忘记了自动布局或其他步骤？

    override func viewDidLoad() {
        super.viewDidLoad()
        let image = UIImage(named: "1-landscape.png")!
        let scaleFactor = image.size.height / image.size.width
        let width = view.frame.size.width
        let height = width * scaleFactor
        let size = CGSize(width: width, height: height)
        let imageView = UIImageView(image: image)
//        imageView.translatesAutoresizingMaskIntoConstraints = false
        imageView.backgroundColor = UIColor.blackColor()
        imageView.contentMode = .ScaleAspectFit
        imageView.frame.size = size
        imageView.center = view.center
        view.addSubview(imageView)
//        var collector = [NSLayoutConstraint]()
//        collector.appendContentsOf(NSLayoutConstraint.constraintsWithVisualFormat("H:|-0-[imageView]-0-|", options: [], metrics: nil, views: ["imageView": imageView]))
//        collector.append(NSLayoutConstraint(item: imageView, attribute: .CenterY, relatedBy: .Equal, toItem: view, attribute: .CenterY, multiplier: 1, constant: 0))
//        view.addConstraints(collector)
    }

Answer 1

用锁定纵横比的约束来强制高度，就成功了。

override func viewDidLoad() {
        super.viewDidLoad()
        let image = UIImage(named: "1-landscape.png")!
        let imageView = UIImageView(image: image)
        imageView.translatesAutoresizingMaskIntoConstraints = false
        imageView.backgroundColor = UIColor.blackColor()
        imageView.contentMode = .ScaleAspectFit
        view.addSubview(imageView)
        var collector = [NSLayoutConstraint]()
        collector.appendContentsOf(NSLayoutConstraint.constraintsWithVisualFormat("H:|-0-[imageView]-0-|", options: [], metrics: nil, views: ["imageView": imageView]))
        collector.append(NSLayoutConstraint(item: imageView, attribute: .Height, relatedBy: .Equal, toItem: imageView, attribute: .Width, multiplier: image.size.height / image.size.width, constant: 0))
        collector.append(NSLayoutConstraint(item: imageView, attribute: .CenterY, relatedBy: .Equal, toItem: view, attribute: .CenterY, multiplier: 1, constant: 0))
        view.addConstraints(collector)
    }