UINavigationItem TitleView消失了

Question

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

当我将第二个视图控制器推送到堆栈上并尝试为此视图控制器设置titleView时，它不起作用。titleView会迅速出现和消失。当我返回到上一个视图控制器时，这个titleView也很快出现和消失了。

有谁知道为什么会发生这种情况，或者如何正确设置titleView而不闪烁和消失？

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

我找到了一个解决方案。我将addTitleView()方法从FirstViewController复制到SecondViewController中，并在viewDidLoad()中调用这两个方法。这就是我想要的效果。由于某些原因，将titleView作为属性向前传递并将其分配给navigationItem.titleView是行不通的。

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，而且很管用：

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不是零。

如何让它再次发生，两个步骤: 1. UIViewController A和B；A有自定义的navigationItem.titleView，B将navigationBar隐藏在它的viewWillAppear()中；当B弹出时，A.viewWillAppear() setNavigationBar(隐藏: false，navigationBar：true) 2.举手取消用户驱动的popViewController。

然后你会发现，A的navigationBar是空的。

Answer 3

我也遇到了同样的问题，但上面的解决方案都没有解决这个问题。我的问题是我将translatesAutoresizingMaskIntoConstraints设置为false。我认为这会导致出现/消失，因为需要将其设置为true，以便在内部将视图约束到导航栏。