Question

在尝试以编程方式向UITableViewCell's contentView添加约束时，我遇到了问题。

在cellForRowAt中，我以编程方式创建UITextView，然后尝试应用约束并将其添加到单元格的contentView中。

然而，我得到了崩溃和错误：

The view hierarchy is not prepared for the constraint: <NSLayoutConstraint:0x1700951d0 UITableViewCellContentView:0x12de3e150.leading == UITextView:0x12e891400.leading + 8   (inactive)>
    When added to a view, the constraint's items must be descendants of that view (or the view itself). This will crash if the constraint needs to be resolved before the view hierarchy is assembled.

我的以下代码：

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
{
    // Dequeue the cell to load data
    let cell: UITableViewCell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)

    if indexPath.section == 1
    {            
        let textView: UITextView = UITextView()

        textView.textColor = UIColor.black
        textView.translatesAutoresizingMaskIntoConstraints = false

        cell.addSubview(textView)

        let leadingConstraint = NSLayoutConstraint(item: cell.contentView, attribute: NSLayoutAttribute.leading, relatedBy: NSLayoutRelation.equal, toItem: textView, attribute: NSLayoutAttribute.leading, multiplier: 1.0, constant: 8.0)

        let trailingConstraint = NSLayoutConstraint(item: cell.contentView, attribute: NSLayoutAttribute.trailing, relatedBy: NSLayoutRelation.equal, toItem: textView, attribute: NSLayoutAttribute.trailing, multiplier: 1.0, constant: -8.0)

        cell.contentView.addConstraint(leadingConstraint)
        cell.contentView.addConstraint(trailingConstraint)

        let topConstraint = NSLayoutConstraint(item: cell.contentView, attribute: NSLayoutAttribute.top, relatedBy: NSLayoutRelation.equal, toItem: textView, attribute: NSLayoutAttribute.top, multiplier: 1.0, constant: 0)

        let bottomConstraint = NSLayoutConstraint(item: cell.contentView, attribute: NSLayoutAttribute.bottom, relatedBy: NSLayoutRelation.equal, toItem: textView, attribute: NSLayoutAttribute.bottom, multiplier: 1.0, constant: 0)

        cell.contentView.addConstraint(topConstraint)
        cell.contentView.addConstraint(bottomConstraint)
    }

    return cell
}

我确实看到了很多关于上述错误的问题，但在应用于UITableViewCell时没有找到关于此错误的问题。

有人能指出我正确的方向吗？

感谢。

Answer 1

将textView添加到 cell.contentView （不是单元格）。所以，让我们改为cell.contentView.addSubview(textView)，它正在发挥作用！

UITableViewCell：以编程方式从UITextView添加约束到内容视图？

1 个答案: