编程约束在 UICollectionViewCell 中不起作用 Swift

Question

我试图在 UICollectionViewCell 中创建一个编程视图，我认为将 "programatically view code" 放在 UICollectionViewCell 中是明智的。

所以这是我的代码：

override func awakeFromNib() {
        super.awakeFromNib()

        let view = UIView()
        view.frame = CGRect.zero
        view.backgroundColor = UIColor.black

        self.contentView.addSubview(view)
        self.contentView.translatesAutoresizingMaskIntoConstraints = false

        NSLayoutConstraint.activate([
            view.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 0),
            view.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: 0),
            view.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: 25),
            view.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 25),
            ])

        self.contentView.layoutIfNeeded()
    }

我想知道为什么自动布局不起作用，如果我使用手动 CGRect，视图确实出现了。

Answer 1

This Solve it just needs to set view.translatesAutoresizingMaskIntoConstraints = false not The contenView

override func awakeFromNib() {
    super.awakeFromNib()

    let view = UIView()
    view.frame = CGRect.zero
    view.backgroundColor = UIColor.black


    self.contentView.addSubview(view)
    view.translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([
        view.topAnchor.constraint(equalTo: self.contentView.topAnchor, constant: 0),
        view.bottomAnchor.constraint(equalTo: self.contentView.bottomAnchor, constant: 0),
        view.trailingAnchor.constraint(equalTo: self.contentView.trailingAnchor, constant: 25),
        view.leadingAnchor.constraint(equalTo: self.contentView.leadingAnchor, constant: 25),
        ])
}

Answer 2

努力改变 self.contentView.translatesAutoresizingMaskIntoConstraints = false 到： view.translatesAutoresizingMaskIntoConstraints = false

您想要关闭 view 的 translatesAutoresizingMaskIntoConstraints，因为我们要对其应用 autolayout。

Answer 3

首先：你不应该调用layoutIfNeeded方法，自动布局循环会在你改变规则（约束）后为你做这件事

其次：要布局的视图应该设置translatesAutoresizingMaskIntoConstraints属性到false，所以你不应该这样做这个

self.contentView.translatesAutoresizingMaskIntoConstraints = false

但你应该这样做

view.translatesAutoresizingMaskIntoConstraints = false

That's because autoresizing mask constraints are applied to your view with constraints that you've set. This may and probably will cause constraints break.

如果这没有帮助，则提供带有自动布局错误的控制台输出。

编程约束在 UICollectionViewCell 中不起作用 Swift

Programatically constraint doesn't work inside UICollectionViewCell Swift

ios

autolayout

uicollectionview

uicollectionviewcell

swift