由于NSLayoutConstraint错误，带有automaticDimension的UITableView不会动态增加大小

问题描述 投票：0回答：2

我正在创建一个自定义UITableViewCell。现在，我想要的只是左边有一个UIButton（checkButton），按钮右边有两个UILabels（titleLabel和notesLabel）。

基本上，它应该看起来像一个标准的UITableViewCell与图像和两个文本标签（但请不要告诉我只是重新使用标准单元格，因为我不能出于各种原因这样做）。按钮应具有固定大小（16x16）并在单元格中垂直居中。这两个标签应该换行并展开以适合其内容。我正在尝试以编程方式定义此单元格，因此我创建了下面的初始化程序来定义约束。

override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
    super.init(style: style, reuseIdentifier: reuseIdentifier)
    titleLabel.translatesAutoresizingMaskIntoConstraints = false
    titleLabel.font = UIFont.systemFont(ofSize: 16)
    titleLabel.lineBreakMode = .byWordWrapping
    titleLabel.numberOfLines = 0
    contentView.addSubview(titleLabel)
    checkButton.translatesAutoresizingMaskIntoConstraints = false
    contentView.addSubview(checkButton)
    notesLabel.translatesAutoresizingMaskIntoConstraints = false
    notesLabel.font = UIFont.systemFont(ofSize: 13)
    notesLabel.lineBreakMode = .byWordWrapping
    notesLabel.numberOfLines = 0
    contentView.addSubview(notesLabel)
    addConstraint(NSLayoutConstraint(item: titleLabel,
                                     attribute: .top,
                                     relatedBy: .equal,
                                     toItem: contentView,
                                     attribute: .top,
                                     multiplier: 1,
                                     constant: 0))
    addConstraint(NSLayoutConstraint(item: notesLabel,
                                     attribute: .top,
                                     relatedBy: .equal,
                                     toItem: titleLabel,
                                     attribute: .bottom,
                                     multiplier: 1,
                                     constant: 0))
    addConstraint(NSLayoutConstraint(item: titleLabel,
                                     attribute: .trailing,
                                     relatedBy: .equal,
                                     toItem: contentView,
                                     attribute: .trailing,
                                     multiplier: 1,
                                     constant: -10))
    addConstraint(NSLayoutConstraint(item: notesLabel,
                                     attribute: .trailing,
                                     relatedBy: .equal,
                                     toItem: contentView,
                                     attribute: .trailing,
                                     multiplier: 1,
                                     constant: -10))
    addConstraint(NSLayoutConstraint(item: notesLabel,
                                     attribute: .bottom,
                                     relatedBy: .equal,
                                     toItem: contentView,
                                     attribute: .bottom,
                                     multiplier: 1,
                                     constant: 0))
    addConstraint(NSLayoutConstraint(item: checkButton,
                                     attribute: .leading,
                                     relatedBy: .equal,
                                     toItem: contentView,
                                     attribute: .leading,
                                     multiplier: 1,
                                     constant: 20))
    addConstraint(NSLayoutConstraint(item: checkButton,
                                     attribute: .centerY,
                                     relatedBy: .equal,
                                     toItem: contentView,
                                     attribute: .centerY,
                                     multiplier: 1,
                                     constant: 0))
    addConstraint(NSLayoutConstraint(item: checkButton,
                                     attribute: .height,
                                     relatedBy: .equal,
                                     toItem: nil,
                                     attribute: .notAnAttribute,
                                     multiplier: 0,
                                     constant: 16))
    addConstraint(NSLayoutConstraint(item: checkButton,
                                     attribute: .width,
                                     relatedBy: .equal,
                                     toItem: nil,
                                     attribute: .notAnAttribute,
                                     multiplier: 0,
                                     constant: 16))
    addConstraint(NSLayoutConstraint(item: notesLabel,
                                     attribute: .leading,
                                     relatedBy: .equal,
                                     toItem: checkButton,
                                     attribute: .trailing,
                                     multiplier: 1,
                                     constant: 12))
    addConstraint(NSLayoutConstraint(item: titleLabel,
                                     attribute: .leading,
                                     relatedBy: .equal,
                                     toItem: checkButton,
                                     attribute: .trailing,
                                     multiplier: 1,
                                     constant: 12))
}

当我运行此代码时，它主要按预期工作，除了Xcode打印以下警告：[Warning] Warning once only: Detected a case where constraints ambiguously suggest a height of zero for a tableview cell's content view. We're considering the collapse unintentional and using standard height instead.

我通常会忽略这一点，但它似乎阻止了单元扩展以适应其内容。例如，如果其中一个标签的内容足以扩展到3行，则只显示第一行。我想要的行为是扩展标签（以及扩展名，单元格）以适应其内容。我对高度限制做错了什么？

ios swift uitableview autolayout nslayoutconstraint
2个回答
1
投票

注意：请在Cell中添加标签和按钮，而不是在单元格的contentView中。下面的代码将工作，请检查并告诉我任何问题。

override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
    super.init(style: style, reuseIdentifier: reuseIdentifier)

    addSubview(titleLabel)
    addSubview(checkButton)
    addSubview(notesLabel)

    titleLabel.translatesAutoresizingMaskIntoConstraints = false
    titleLabel.font = UIFont.systemFont(ofSize: 16)
    titleLabel.lineBreakMode = .byWordWrapping
    titleLabel.numberOfLines = 0

    checkButton.translatesAutoresizingMaskIntoConstraints = false

    notesLabel.translatesAutoresizingMaskIntoConstraints = false
    notesLabel.font = UIFont.systemFont(ofSize: 13)
    notesLabel.lineBreakMode = .byWordWrapping
    notesLabel.numberOfLines = 0

    addConstraint(NSLayoutConstraint(item: titleLabel,
                                     attribute: .top,
                                     relatedBy: .equal,
                                     toItem: self,
                                     attribute: .top,
                                     multiplier: 1,
                                     constant: 0))
    addConstraint(NSLayoutConstraint(item: notesLabel,
                                     attribute: .top,
                                     relatedBy: .equal,
                                     toItem: titleLabel,
                                     attribute: .bottom,
                                     multiplier: 1,
                                     constant: 0))
    addConstraint(NSLayoutConstraint(item: titleLabel,
                                     attribute: .trailing,
                                     relatedBy: .equal,
                                     toItem: self,
                                     attribute: .trailing,
                                     multiplier: 1,
                                     constant: -10))
    addConstraint(NSLayoutConstraint(item: notesLabel,
                                     attribute: .trailing,
                                     relatedBy: .equal,
                                     toItem: self,
                                     attribute: .trailing,
                                     multiplier: 1,
                                     constant: -10))
    addConstraint(NSLayoutConstraint(item: notesLabel,
                                     attribute: .bottom,
                                     relatedBy: .equal,
                                     toItem: self,
                                     attribute: .bottom,
                                     multiplier: 1,
                                     constant: 0))
    addConstraint(NSLayoutConstraint(item: checkButton,
                                     attribute: .leading,
                                     relatedBy: .equal,
                                     toItem: self,
                                     attribute: .leading,
                                     multiplier: 1,
                                     constant: 20))
    addConstraint(NSLayoutConstraint(item: checkButton,
                                     attribute: .centerY,
                                     relatedBy: .equal,
                                     toItem: self,
                                     attribute: .centerY,
                                     multiplier: 1,
                                     constant: 0))
    addConstraint(NSLayoutConstraint(item: checkButton,
                                     attribute: .height,
                                     relatedBy: .equal,
                                     toItem: nil,
                                     attribute: .notAnAttribute,
                                     multiplier: 0,
                                     constant: 16))
    addConstraint(NSLayoutConstraint(item: checkButton,
                                     attribute: .width,
                                     relatedBy: .equal,
                                     toItem: nil,
                                     attribute: .notAnAttribute,
                                     multiplier: 0,
                                     constant: 16))
    addConstraint(NSLayoutConstraint(item: notesLabel,
                                     attribute: .leading,
                                     relatedBy: .equal,
                                     toItem: checkButton,
                                     attribute: .trailing,
                                     multiplier: 1,
                                     constant: 12))
    addConstraint(NSLayoutConstraint(item: titleLabel,
                                     attribute: .leading,
                                     relatedBy: .equal,
                                     toItem: checkButton,
                                     attribute: .trailing,
                                     multiplier: 1,
                                     constant: 12))
}
0
投票

这是我的方法

private func setUp() {
    self.selectionStyle = .none
    self.contentView.backgroundColor = .white

    let button = UIButton(frame: CGRect(x: 0, y: 0, width: 16, height: 16))
    button.setImage(UIImage(named: "arrow"), for: .normal)
    button.translatesAutoresizingMaskIntoConstraints = false
    self.contentView.addSubview(button)
    button.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 8.0).isActive = true
    button.centerYAnchor.constraint(equalTo: self.contentView.centerYAnchor).isActive = true
    button.widthAnchor.constraint(equalToConstant: button.frame.width).isActive = true
    button.heightAnchor.constraint(equalToConstant: button.frame.height).isActive = true

    let view = UIView()
    view.backgroundColor = .red
    view.translatesAutoresizingMaskIntoConstraints = false
    self.contentView.addSubview(view)
    view.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 8.0).isActive = true
    view.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: button.frame.width + 16.0).isActive = true
    view.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: 8.0).isActive = true
    view.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: -8.0).isActive = true

    titleLabel.translatesAutoresizingMaskIntoConstraints = false
    titleLabel.numberOfLines = 0
    view.addSubview(titleLabel)
    titleLabel.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
    titleLabel.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
    titleLabel.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true

    notesLabel.translatesAutoresizingMaskIntoConstraints = false
    notesLabel.numberOfLines = 0
    view.addSubview(notesLabel)
    notesLabel.topAnchor.constraint(equalTo: titleLabel.bottomAnchor, constant: 8.0).isActive = true
    notesLabel.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
    notesLabel.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
    notesLabel.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
}

如果标签是多线动态高度，请使用以下命令启用自调整单元格

tableView.rowHeight = UITableView.automaticDimension
tableView.estimatedRowHeight = 44.0

func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
    return UITableView.automaticDimension
}

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