[英]Add NSLayoutConstraint for a view inside a UITableCellView
I would like to have a UIButton centred inside my UITableCellView. 我想在UITableCellView中居中放置一个UIButton。 I've added the necessary code in the tableView cellForRowAt function but I get the error : 我在tableView cellForRowAt函数中添加了必要的代码,但出现错误:
The view hierarchy is not prepared for the constraint: When added to a view, the constraint's items must be descendants of that view (or the view itself). 没有为约束准备视图层次结构:将约束项添加到视图时,其项必须是该视图的后代(或视图本身)。 This will crash if the constraint needs to be resolved before the view hierarchy is assembled. 如果在组装视图层次结构之前需要解决约束,则会崩溃。 Break on -[UIView(UIConstraintBasedLayout) _viewHierarchyUnpreparedForConstraint:] to debug. 中断-[UIView(UIConstraintBasedLayout)_viewHierarchyUnpreparedForConstraint:]进行调试。
My code is the following : 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!
}
Any help would be appreciated ! 任何帮助,将不胜感激 !
Try this 尝试这个
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!
}
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