ios - 带自动布局的侧边菜单

Question

我正在尝试制作一个侧面菜单，但在使用自动布局设置它时遇到一些问题。我有一个 rootViewController，我将 leftMenuVC 添加为 childVC，然后设置约束。

class RootVC: UIViewController, NavigationBarDelegate {
    var leftMenuVC: UIViewController?
    var navigationBar = NavigationBar()
    var isMenuCollapsed = true

    override func viewDidLoad() {
        leftMenuVC = leftVC()
        addChildViewController(leftMenuVC!)
        view.addSubview(leftMenuVC!.view)
        leftMenuVC!.didMove(toParentViewController: self)
    }

    override func viewDidLayoutSubviews() {
        if let v = leftMenuVC?.view {
            v.translatesAutoresizingMaskIntoConstraints = false
            v.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
            v.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
            v.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -140).isActive = true
            v.bottomAnchor.constraint(equalTo: view.bottomAnchor).isActive = true
        }
    }

    func menuButtonClicked(){

    }
}

所以我的问题是如何更改约束以隐藏/显示菜单并支持方向

Answer 1

当我想在屏幕之外隐藏带有约束的 View 时，我通常会做的是:

1 设置所有约束以使侧 View 可见(处于事件状态)

2 保留引用将侧 View 固定在一侧(此处为左侧)的约束

leftAnchor = NSLayoutConstraint(item: v, attribute: .left, relatedBy: .equal, toItem: view, attribute: .left, multiplier: 1, constant: 0)
view.addConstraint(leftAnchor)
view.addConstraint(NSLayoutConstraint(item: v, attribute: .top, relatedBy: .equal, toItem: view, attribute: .top, multiplier: 1, constant: 0))
view.addConstraint(NSLayoutConstraint(item: v, attribute: .bottom, relatedBy: .equal, toItem: view, attribute: .bottom, multiplier: 1, constant: 0))
view.addConstraint(NSLayoutConstraint(item: v, attribute: .width, relatedBy: .equal, toItem: view, attribute: .width, multiplier: 0.6, constant: 0))

3 再设置一个约束，以便隐藏 View 。通常是这样的。请注意，优先级设置为 999 以避免约束冲突。

var hiddingConstraint = NSLayoutConstraint(item: v, attribute: .right, relatedBy: .equal, toItem: view, attribute: .left, multiplier: 1, constant: 0)
hiddingConstraint.priority = 999
view.addConstraint(hiddingConstraint)

4 通过激活或不激活 leftAnchor 来制作动画

UIView.animate(withDuration: 0.3) {
       self.leftAnchor.active = false
       self.view.layoutIfNeeded()
}

所以你最终应该得到这样的代码:

class RootVC: UIViewController, NavigationBarDelegate {
    var leftMenuVC: UIViewController?
    var navigationBar = NavigationBar()
    var isMenuCollapsed = true {
        didSet {
            UIView.animate(withDuration: 0.3) {
                self.leftAnchor?.isActive = self.isMenuCollapsed
                self.view.layoutIfNeeded()
            }
        }

    }
    var leftAnchor : NSLayoutConstraint?

    override func viewDidLoad() {
        leftMenuVC = leftVC()
        addChildViewController(leftMenuVC!)
        view.addSubview(leftMenuVC!.view)
        leftMenuVC!.didMove(toParentViewController: self)
    }

    override func viewDidLayoutSubviews() {
        if let v = leftMenuVC?.view {

            leftAnchor = NSLayoutConstraint(item: v, attribute: .left, relatedBy: .equal, toItem: view, attribute: .left, multiplier: 1, constant: 0)
            view.addConstraint(leftAnchor!)
            view.addConstraint(NSLayoutConstraint(item: v, attribute: .top, relatedBy: .equal, toItem: view, attribute: .top, multiplier: 1, constant: 0))
            view.addConstraint(NSLayoutConstraint(item: v, attribute: .bottom, relatedBy: .equal, toItem: view, attribute: .bottom, multiplier: 1, constant: 0))
            view.addConstraint(NSLayoutConstraint(item: v, attribute: .width, relatedBy: .equal, toItem: view, attribute: .width, multiplier: 0.6, constant: 0))

            var hiddingConstraint = NSLayoutConstraint(item: v, attribute: .right, relatedBy: .equal, toItem: view, attribute: .left, multiplier: 1, constant: 0)
            hiddingConstraint.priority = 999
            view.addConstraint(hiddingConstraint)
        }
    }

    func menuButtonClicked(){
        isMenuCollapsed = !isMenuCollapsed
    }
}

PS:我不会将约束设置放在 viewDidLayoutSubviews 中，也许放在 viewWillAppear 中，因为您不必每次旋转设备时都设置它们。这就是约束的目的