Question

尝试将渐变颜色设置为以编程方式编写的View Controller上的按钮。但它不会出现！

我尝试添加具有指定索引的子层或在viewdidload闭包中添加渐变子层，仍然没有任何效果！

private let getStartButton : UIButton = {
        let button = UIButton(type: .system)
        button.translatesAutoresizingMaskIntoConstraints = false
        button.setTitle("GET STARTED", for: .normal)
        button.addTarget(self, action: #selector(getStarted), for: .touchUpInside)
        button.titleLabel?.font = UIFont.boldSystemFont(ofSize: 14)
        button.layer.cornerRadius = 5
        button.clipsToBounds = true
        button.isHidden = false
        let gradientLayer = CAGradientLayer()
        gradientLayer.colors = [UIColor.lightGreyBlue.cgColor, UIColor.sea.cgColor]
        gradientLayer.startPoint = CGPoint(x: 0, y: 0)
        gradientLayer.endPoint = CGPoint(x: 1, y: 1)
        gradientLayer.frame = button.bounds

        button.layer.addSublayer(gradientLayer)


        return button

    }()


    fileprivate func setupBottomControls() {

        view.addSubview(getStartButton)
        getStartButton.bottomAnchor.constraint(equalTo: view.bottomAnchor, constant: -12).isActive = true
        getStartButton.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 12).isActive = true
        getStartButton.widthAnchor.constraint(equalToConstant: UIScreen.main.bounds.size.width-32
        ).isActive = true
        getStartButton.heightAnchor.constraint(equalToConstant: 50).isActive = true

    }

它仅显示按钮的标题。

Answer 1

你在说

gradientLayer.frame = button.bounds

但是按钮没有边界。因此该图层没有框架。

在viewDidLayoutSubviews之后，在自动布局约束生效之前，按钮将没有任何大小。

如何在以编程方式编写的视图上正确显示CAGradientLayer？

1 个答案: