作为子视图添加到集合视图单元格时，滚动视图中的内容不可见

Question

我有一个集合视图，其中包含一个滚动视图作为子视图，并且已经向滚动视图添加了一个文本视图，但是看不到该文本视图。 我为集合视图单元格使用了自定义类。 这是代码：

class CustomReaderPageClass: UICollectionViewCell {

    fileprivate let scrollView: UIScrollView = {

        let sv = UIScrollView()
        sv.backgroundColor = .green
        sv.contentSize.height = 1200
        return sv

    }()

    fileprivate let chapterBody: UITextView = {

        let textView = UITextView()
        textView.text = "2019"
        textView.font = UIFont(name: "Avenir", size: 18)
        textView.isEditable = false
        textView.backgroundColor = .yellow//UIColor.init(red: 210/255, green: 198/255, blue: 194/255, alpha: 1)
        return textView

    }()

    override init(frame: CGRect) {
        super.init(frame: frame)

        contentView.addSubview(scrollView)

        scrollView.translatesAutoresizingMaskIntoConstraints = false
        scrollView.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 0).isActive = true
        scrollView.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 0).isActive = true
        scrollView.trailingAnchor.constraint(equalTo: contentView.trailingAnchor, constant: 0).isActive = true
        scrollView.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: 0).isActive = true

        scrollView.addSubview(chapterBody)
        // Add the constraints to the chapter body text view
        chapterBody.translatesAutoresizingMaskIntoConstraints = false
        chapterBody.topAnchor.constraint(equalTo: scrollView.safeAreaLayoutGuide.topAnchor, constant: 10).isActive = true
        chapterBody.leadingAnchor.constraint(equalTo: contentView.leadingAnchor).isActive = true
        chapterBody.trailingAnchor.constraint(equalTo: contentView.trailingAnchor).isActive = true
        chapterBody.heightAnchor.constraint(equalToConstant: 300)

    }
}

我是Swift的初学者。

Answer 1

添加这两个约束

    scrollView.widthAnchor.constraint(equalTo: contentView.widthAnchor, constant: 0).isActive = true
    chapterBody.bottomAnchor.constraint(equalTo:scrollView.bottomAnchor, constant: 0).isActive = true

---

    scrollView.translatesAutoresizingMaskIntoConstraints = false
    scrollView.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 0).isActive = true
    scrollView.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 0).isActive = true
    scrollView.trailingAnchor.constraint(equalTo: contentView.trailingAnchor, constant: 0).isActive = true
    scrollView.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: 0).isActive = true
    scrollView.widthAnchor.constraint(equalTo: contentView.widthAnchor, constant: 0).isActive = true

    scrollView.addSubview(chapterBody)
    // Add the constraints to the chapter body text view
    chapterBody.translatesAutoresizingMaskIntoConstraints = false
    chapterBody.topAnchor.constraint(equalTo: scrollView.safeAreaLayoutGuide.topAnchor, constant: 10).isActive = true
    chapterBody.leadingAnchor.constraint(equalTo: scrollView.leadingAnchor).isActive = true
    chapterBody.trailingAnchor.constraint(equalTo: scrollView.trailingAnchor).isActive = true
    chapterBody.heightAnchor.constraint(equalToConstant: 300)
    chapterBody.bottomAnchor.constraint(equalTo:scrollView.bottomAnchor, constant: 0).isActive = true