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ios - CAGradientLayer 未应用于整个屏幕

问题描述

我正在尝试将渐变图层应用于屏幕，但令人讨厌的是该图层仅占屏幕的一半。

我认为问题似乎来自这里的这个问题：

descriptionTextView.topAnchor.constraint(equalTo: view.centerYAnchor).isActive = true

这是我第一次使用编程约束，所以我很难看出问题出在哪里。

这是发生的事情的图像

这是下面的代码

class OBP1VC: UIViewController {

    let gradientLayer: CAGradientLayer = {
        let caGradient = CAGradientLayer()
        caGradient.frame = UIScreen.main.bounds
        caGradient.colors = [Colours.brightGreen.cgColor, Colours.midBlue.cgColor]
        caGradient.startPoint = CGPoint(x: 0.0, y: 0.0)
        caGradient.endPoint = CGPoint(x: 1.0, y: 1.0)
        return caGradient
    }()

    let bearImageView: UIImageView = {
        let imageView = UIImageView(image: #imageLiteral(resourceName: "br_flag"))
        imageView.translatesAutoresizingMaskIntoConstraints = false
        return imageView
    }()

    let descriptionTextView: UITextView = {
        let textView = UITextView()
        textView.text = "Hello\n\nWelcome to the new\n\nHome Healthcare"
        textView.translatesAutoresizingMaskIntoConstraints = false
        textView.textAlignment = .center
        textView.isUserInteractionEnabled = false
        textView.font = UIFont(name: Fonts.avenirBlack, size: 20.0)
        return textView
    }()

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        view.addSubview(bearImageView)
        view.addSubview(descriptionTextView)

        setupLayout()
    }

    override func viewDidLayoutSubviews() {
        view.layer.insertSublayer(gradientLayer, at: 0)
    }

    private func setupLayout() {

        bearImageView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        bearImageView.topAnchor.constraint(equalTo: view.topAnchor, constant: 100).isActive = true
        bearImageView.widthAnchor.constraint(equalToConstant: 100).isActive = true
        bearImageView.heightAnchor.constraint(equalToConstant: 100).isActive = true

        descriptionTextView.topAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
        descriptionTextView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
        descriptionTextView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
        descriptionTextView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
    }
}

标签： iosswiftxcodeconstraintscagradientlayer

解决方案

在上面的代码中textView的背景颜色覆盖了渐变布局，所以清除它会使渐变可见

您的 setupLayout 方法应如下所示 -

private func setupLayout() {

        bearImageView.backgroundColor = UIColor.red
        bearImageView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        bearImageView.topAnchor.constraint(equalTo: view.topAnchor, constant: 100).isActive = true
        bearImageView.widthAnchor.constraint(equalToConstant: 100).isActive = true
        bearImageView.heightAnchor.constraint(equalToConstant: 100).isActive = true

        descriptionTextView.topAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
        descriptionTextView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
        descriptionTextView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
        descriptionTextView.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
        descriptionTextView.backgroundColor = UIColor.clear
    }

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