布局限制不适用于iOS swift

Question

我添加了前导|尾随|顶部|高度约束，但视图不可见。

let view = UIView()
view.backgroundColor = .orange
self.addSubview(view)

NSLayoutConstraint.activate([
view.leadingAnchor.constraint(equalTo: self.leadingAnchor),
view.trailingAnchor.constraint(equalTo: self.trailingAnchor),
view.topAnchor.constraint(equalTo: self.topAnchor, constant: 100),
view.heightAnchor.constraint(equalToConstant: 300)
])

Answer 1

将视图添加为子视图时，您的代码应该禁用translatesAutoresizingMaskIntoConstraints。这意味着系统不会创建一组与视图的自动重影掩码指定的行为重复的约束。

假设您的约束是正确的，您应该在将属性设置为false后看到您的视图出现。

let view = UIView()
view.backgroundColor = .orange
view.translatesAutoresizingMaskIntoConstraints = false
self.addSubview(view)

NSLayoutConstraint.activate([
view.leadingAnchor.constraint(equalTo: self.leadingAnchor),
view.trailingAnchor.constraint(equalTo: self.trailingAnchor),
view.topAnchor.constraint(equalTo: self.topAnchor, constant: 100),
view.heightAnchor.constraint(equalToConstant: 300)
])