UINavigationItem TitleView消失

Question

我正在尝试为导航栏创建自定义titleView。我可以在导航控制器中嵌入的根视图控制器中设置titleView。

当我将第二个视图控制器推到堆栈上并尝试为该视图控制器设置titleView时，它不起作用。 titleView快速出现并消失。当我回到上一个视图控制器时，此titleView迅速出现，现在也消失了。

有人知道为什么会这样，或者如何正确设置titleView而不会闪烁和消失吗？

class FirstViewController: UIViewController {

    var titleView: UIView!

    override func viewDidLoad() {
        super.viewDidLoad()
        addTitleView()
    }

    func addTitleView() {
        titleView = UIView(frame: CGRect(x: 0, y: 0, width: 150, height: 44))

        let companyLabel = UILabel(frame: CGRect(x: 0, y: 3, width: 150, height: 11))
        companyLabel.text = "CPS Dashboard"
        companyLabel.textColor = UIColor.grayColor()
        companyLabel.textAlignment = .Center
        companyLabel.font = UIFont.systemFontOfSize(9)
        titleView.addSubview(companyLabel)

        let titleLabel = UILabel(frame: CGRect(x: 0, y: 16, width: 150, height: 18))
        titleLabel.text = "Dashboard"
        titleLabel.textColor = UIColor.blackColor()
        titleLabel.textAlignment = .Center
        titleLabel.font = UIFont.systemFontOfSize(15)
        titleView.addSubview(titleLabel)

        navigationItem.titleView = titleView
    }

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if segue.identifier == "Show" {
            let controller = segue.destinationViewController as! SecondViewController
            controller.titleView = titleView
        }
    }
}

第二个视图控制器：

class SecondViewController: UIViewController {

    var titleView: UIView?

    override func viewDidLoad() {
        super.viewDidLoad()

        if let titleView = titleView {
            navigationItem.titleView = titleView
        }
    }
}

Answer 1

我找到了解决方案。我将addTitleView（）方法从FirstViewController复制到SecondViewController，并在viewDidLoad（）中将它们都调用了。这完全符合我的期望。由于某种原因，它无法将titleView作为属性向前传递并将其分配给navigationItem.titleView。

class FirstViewController: UIViewController {

    var titleView: UIView!

    override func viewDidLoad() {
        super.viewDidLoad()
        addTitleView()
    }

    func addTitleView() {
        titleView = UIView(frame: CGRect(x: 0, y: 0, width: 150, height: 44))

        let companyLabel = UILabel(frame: CGRect(x: 0, y: 3, width: 150, height: 11))
        companyLabel.text = "CPS Dashboard"
        companyLabel.textColor = UIColor.grayColor()
        companyLabel.textAlignment = .Center
        companyLabel.font = UIFont.systemFontOfSize(9)
        titleView.addSubview(companyLabel)

        let titleLabel = UILabel(frame: CGRect(x: 0, y: 16, width: 150, height: 18))
        titleLabel.text = "Dashboard"
        titleLabel.textColor = UIColor.blackColor()
        titleLabel.textAlignment = .Center
        titleLabel.font = UIFont.systemFontOfSize(15)
        titleView.addSubview(titleLabel)

        navigationItem.titleView = titleView
    }
}

第二个视图控制器：

class SecondViewController: UIViewController {

    var titleView: UIView!

    override func viewDidLoad() {
        super.viewDidLoad()
        addTitleView()
    }

    func addTitleView() {
        titleView = UIView(frame: CGRect(x: 0, y: 0, width: 150, height: 44))

        let companyLabel = UILabel(frame: CGRect(x: 0, y: 3, width: 150, height: 11))
        companyLabel.text = "CPS Dashboard"
        companyLabel.textColor = UIColor.grayColor()
        companyLabel.textAlignment = .Center
        companyLabel.font = UIFont.systemFontOfSize(9)
        titleView.addSubview(companyLabel)

        let titleLabel = UILabel(frame: CGRect(x: 0, y: 16, width: 150, height: 18))
        titleLabel.text = "Dashboard"
        titleLabel.textColor = UIColor.blackColor()
        titleLabel.textAlignment = .Center
        titleLabel.font = UIFont.systemFontOfSize(15)
        titleView.addSubview(titleLabel)

        navigationItem.titleView = titleView
    }
}

Answer 2

我的解决方案很简单，并且有效：

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    if let tv = navigationItem.titleView {
        print("transform", tv.transform)) // is always identity
        let bounds = tv.bounds
        print("bounds", bounds) // its origin may not be zero.
        tv.bounds = CGRect(origin: .zero, size: bounds.size)
        print("new bounds", tv.bounds)
    }
}

使用Xcode的视图调试器，您会发现titleView.bounds.origin不为零。如何使其再次发生，分两个步骤：1. UIViewController A和B; A具有自定义navigationItem.titleView，B将navigationBar隐藏在其viewWillAppear()中；当B弹出时，A.viewWillAppear（）setNavigationBar（隐藏：false，动画：true）2.抬起手，取消用户驱动的popViewController。然后您会发现A的navigationBar为空白。

Answer 3

我遇到了同样的问题，但是以上解决方案都没有为我解决。我的问题是我将translatesAutoresizingMaskIntoConstraints设置为false。我想这会导致出现/消失，因为需要将其设置为true才能将视图内部限制在导航栏中。