2

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hide功能不起作用，heightAnchor不起作用。

4

3 回答 3

7

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 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
}

如果你想要你也可以动画变化，像这样：

func hide(){
    heightArchonWhenShow.isActive = false
    heightArchonWhenHide.isActive = true

    UIView.animate(withDuration: 0.3) {
        self.view.layoutIfNeeded()
    }
}
于 2018-12-12T09:42:55.043 回答
2

你只需要 1 个变量

var heightCon = view.heightAnchor.constraint(equalToConstant: view.frame.height - 300)
heightCon.isActive = true

然后管理它的恒定值

func showOrHide(_ te:Bool){

   heightCon.constant = te ? view.frame.height - 300 : view.frame.height + 300

     UIView.animate(withDuration: 0.3) {
        self.view.layoutIfNeeded()
    }
}
于 2018-12-12T10:24:30.967 回答
1

我建议你在不同的函数中设置你的约束，比如可能setup()，并将它们存储在一些你可以修改的变量中，我会给你一个例子

var constraint: NSLayoutConstraint?

func setup() {
    constraint = view.heightAnchor.constraint(equalToConstant: view.frame.height)
}

func show() {
    if constraint != nil {
        constraint!.constant = constraint!.constant + 300
    }
}

func hide() {
    if constraint != nil {
        constraint!.constant = constraint!.constant - 300
    }
}
于 2018-12-12T09:39:02.200 回答