自动布局未正确设置图像视图框架

debugcn 发表于 Dev

用户1951992

只需将此图像放置在图像视图中并设置为宽高比。

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)
    }

在运行时，视图的高度比图像的高度大50％。为什么？？？

如果我们使用传统的观点发表意见，那就没有问题。我会忘记自动布局之类的步骤吗？

    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)
    }

用户1951992

可以通过锁定纵横比的约束来强制高度，从而达到目的。

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)
    }

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