为 UITableCellView 中的视图添加 NSLayoutConstraint

Question

我希望在我的 UITableCellView 中居中放置一个 UIButton。我在 tableView cellForRowAt 函数中添加了必要的代码，但出现错误：

视图层次结构未为约束准备：添加到视图时，约束的项目必须是该视图（或视图本身）的后代。如果在组装视图层次结构之前需要解决约束，这将崩溃。打断 -[UIView(UIConstraintBasedLayout) _viewHierarchyUnpreparedForConstraint:] 进行调试。

我的代码如下：

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

            cell = UITableViewCell(
                style: .default, reuseIdentifier: Id.settingButtonCellIdentifier)
            cell!.backgroundColor = UIColor.clear
            cell!.preservesSuperviewLayoutMargins = false
            cell!.separatorInset = UIEdgeInsets.zero

            let button : UIButton = UIButton(type: UIButtonType.custom) as UIButton
            button.backgroundColor = UIColor.red
            button.setTitle("Click Me !", for: UIControlState.normal)

            cell!.addSubview(button)

            button.translatesAutoresizingMaskIntoConstraints = false
            button.addConstraint(NSLayoutConstraint(item: button, attribute: .leading, relatedBy: .equal, toItem: cell!, attribute: .leading, multiplier: 1, constant: 10))
            button.addConstraint(NSLayoutConstraint(item: button, attribute: .trailing, relatedBy: .equal, toItem: cell!, attribute: .trailing, multiplier: 1, constant: 10))
            button.addConstraint(NSLayoutConstraint(item: button, attribute: .top, relatedBy: .equal, toItem: cell!, attribute: .top, multiplier: 1, constant: 10))
            button.addConstraint(NSLayoutConstraint(item: button, attribute: .bottom, relatedBy: .equal, toItem: cell!, attribute: .bottom, multiplier: 1, constant: 10))
        }

        return cell!
    }

如有任何帮助，我们将不胜感激！

Answer 1

试试这个

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        cell = UITableViewCell(
            style: .default, reuseIdentifier: Id.settingButtonCellIdentifier)
        cell!.backgroundColor = UIColor.clear
        cell!.preservesSuperviewLayoutMargins = false
        cell!.separatorInset = UIEdgeInsets.zero

        let button : UIButton = UIButton(type: UIButtonType.custom) as UIButton
        button.backgroundColor = UIColor.red
        button.setTitle("Click Me !", for: UIControlState.normal)

        button.translatesAutoresizingMaskIntoConstraints = false


        cell!.contentView.addSubview(button)

        cell.contentView.addConstraint(NSLayoutConstraint(item: button, attribute: .leading, relatedBy: .equal, toItem: cell.contentView, attribute: .leading, multiplier: 1, constant: 10))
        cell.contentView.addConstraint(NSLayoutConstraint(item: button, attribute: .trailing, relatedBy: .equal, toItem: cell.contentView, attribute: .trailing, multiplier: 1, constant: 10))
        cell.contentView.addConstraint(NSLayoutConstraint(item: button, attribute: .top, relatedBy: .equal, toItem: cell.contentView, attribute: .top, multiplier: 1, constant: 10))
        cell.contentView.addConstraint(NSLayoutConstraint(item: button, attribute: .bottom, relatedBy: .equal, toItem: cell.contentView, attribute: .bottom, multiplier: 1, constant: 10))
    }

    return cell!
}

为 UITableCellView 中的视图添加 NSLayoutConstraint

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