我使用这段代码：
func show(){
view.translatesAutoresizingMaskIntoConstraints = false
view.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 0).isActive = true
view.topAnchor.constraint(equalTo: view.topAnchor, constant: 0).isActive = true
view.heightAnchor.constraint(equalToConstant: view.frame.height - 300).isActive = true
view.rightAnchor.constraint(equalTo: view.rightAnchor, constant: 0).isActive = true
}
func hide(){
view.translatesAutoresizingMaskIntoConstraints = false
view.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 0).isActive = true
view.topAnchor.constraint(equalTo: view.topAnchor, constant: 0).isActive = true
view.heightAnchor.constraint(equalToConstant: view.frame.height + 300).isActive = true
view.rightAnchor.constraint(equalTo: view.rightAnchor, constant: 0).isActive = true
}
show功能工作正常，但是hide功能不起作用并且heightAnchor不起作用。
首先声明约束
var heightArchonWhenShow = view.heightAnchor.constraint(equalToConstant: view.frame.height - 300)
var heightArchonWhenHide = view.heightAnchor.constraint(equalToConstant: view.frame.height + 300)
初始化 ViewDidLoad 的约束后
func setConstraints(){
view.translatesAutoresizingMaskIntoConstraints = false
view.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 0).isActive = true
view.topAnchor.constraint(equalTo: view.topAnchor, constant: 0).isActive = true
view.rightAnchor.constraint(equalTo: view.rightAnchor, constant: 0).isActive = true
heightArchonWhenShow.isActive = true
}
并且简单地激活它们，不要覆盖。像这样：
func show(){
heightArchonWhenShow.isActive = true
heightArchonWhenHide.isActive = false
}
func hide(){
heightArchonWhenShow.isActive = false
heightArchonWhenHide.isActive = true
}
如果你愿意，你也可以动画更改，如下所示：
func hide(){
heightArchonWhenShow.isActive = false
heightArchonWhenHide.isActive = true
UIView.animate(withDuration: 0.3) {
self.view.layoutIfNeeded()
}
}
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