Swift：如何从ViewDidLoad使阴影在UITextView上工作？

Question

我无法获得UITextView内部UIImageView上的阴影。

我尝试了许多可能的方法。约束是，由于某些原因它们不可访问，因此我无法覆盖layoutMethods。因此，为了进行演示，我将相同的代码放入viewDidLoad中进行调试，但无法弄清楚。请在这里解释我做错了。

    override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = .black
        let imageView = UIImageView()
        imageView.image = #imageLiteral(resourceName: "guitar")
        imageView.layer.cornerRadius = 15
        imageView.clipsToBounds = true

        view.addSubview(imageView)
        imageView.translatesAutoresizingMaskIntoConstraints = false
        imageView.heightAnchor.constraint(equalToConstant: 240).isActive = true
        imageView.widthAnchor.constraint(equalToConstant: 240).isActive = true
        imageView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
        imageView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true

        let textView = UITextView(frame: CGRect.zero)
        textView.text = "This is a Sample text. This is a Sample text. This is a Sample text. This is a Sample text. This is a Sample text. "
        textView.isEditable = false
        textView.textAlignment = .left
        textView.isSelectable = false
        textView.backgroundColor = .systemBlue
        textView.textColor = UIColor.white
        textView.sizeToFit()
        textView.isScrollEnabled = false
        textView.textContainerInset = UIEdgeInsets(top: 6, left: 7, bottom: 6, right: 7)
        textView.clipsToBounds = false
        textView.layer.shadowColor = UIColor.gray.cgColor
        textView.layer.shadowRadius = 10
        textView.layer.opacity = 1
        textView.layer.shadowOffset = .zero
        textView.layer.shadowPath = UIBezierPath(rect: textView.bounds).cgPath
        textView.layer.masksToBounds = false

        imageView.addSubview(textView)
        textView.translatesAutoresizingMaskIntoConstraints = false
        textView.leftAnchor.constraint(equalTo: imageView.leftAnchor).isActive = true
        textView.bottomAnchor.constraint(equalTo: imageView.bottomAnchor).isActive = true
        textView.rightAnchor.constraint(equalTo: imageView.rightAnchor).isActive = true
    }

Answer 1

您将LAYER的不透明度设置为1：

textView.layer.opacity = 1

但是您需要设置图层的shadowOpacity：

//textView.layer.opacity = 1

textView.layer.shadowOpacity = 1

应该可以解决问题。

顺便说一下，无论是否使用.shadowPath，您都将获得相同的结果（因为“默认”阴影路径是视图的边界/矩形）。