UINavigationItem TitleView消失

Question

我正在尝试为导航栏创建自定义titleView。我能够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入堆栈并尝试为此视图控制器设置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，这个titleView会很快出现并且现在也消失了。

有谁知道为什么会这样，或者如何正确设置titleView而不闪烁并消失？

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viewcontroller：

class SecondViewController: UIViewController {

    var titleView: UIView?

    override func viewDidLoad() {
        super.viewDidLoad()

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

Answer 1

我的解决方案很简单，而且有效：

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 如何让它再次发生，两个步骤： 1. UIViewController A和B; A有自定义navigationItem.titleView，B在其navigationBar中隐藏viewWillAppear();当B poped时，A.viewWillAppear（）setNavigationBar（hidden：false，animated：true） 2.举起手来取消用户驱动的popViewController 然后你会发现，A navigationBar是空白的。

Answer 2

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arr[1::2]设置为''.join。我想这会导致出现/消失，因为需要将其设置为translatesAutoresizingMaskIntoConstraints才能将视图内部限制在导航栏中。

Answer 3

// show segment control in navigation bar instead of label
@interface XCtrl : UIViewController
{
    UIView *barTitleView;
    UISegmentedControl *barSegment;
}
@end

@implementation XCtrl
- (void)viewWillAppear:(BOOL)animated
{    
    UINavigationItem *navitem = self.tabBarController.navigationItem;
    [barSegment removeFromSuperview];

    // retain title view of previous controller and restore him when view disappears
    barTitleView = navitem.titleView;
    navitem.titleView = barSegment;
}

- (void)viewWillDisappear:(BOOL)animated
{    
    [barSegment removeFromSuperview];
    UINavigationItem *navitem = self.tabBarController.navigationItem;
    navitem.titleView = barTitleView;
}
@end