ios - 页面 View 导航栏标题

Question

我的代码有这个问题，因此我的 PageViewController 有一个函数，它根据用户正在查看的 View 在导航栏上显示 View Controller 的标题。但是，当我运行该应用程序时，它开始时没有标题，并且该功能仅在用户开始滚动页面时才实现。我想知道我是否可以做些什么来解决这个问题？我使用的函数包括一个 switch 语句，可以在下面和整个类的代码中看到:

func pageViewController(pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
        if (!completed) {
            return
        }

        if let firstViewController = viewControllers?.first,
            let arrayIndex = orderedViewControllers.indexOf(firstViewController) {
            switch arrayIndex {
            case 0:
                self.navigationController!.navigationBar.topItem!.title = "Monday"
                break

            case 1:
                self.navigationController!.navigationBar.topItem!.title = "Tuesday"
                break

            case 2:
                self.navigationController!.navigationBar.topItem!.title = "Wednesday"
                break

            case 3:
                self.navigationController!.navigationBar.topItem!.title = "Thursday"

            case 4:
                self.navigationController!.navigationBar.topItem!.title = "Friday"
                break

            case 5:
                self.navigationController!.navigationBar.topItem!.title = "Saturday"
                break

            case 6:
                self.navigationController!.navigationBar.topItem!.title = "Sunday"
                break

            default:
                self.navigationController!.navigationBar.topItem!.title = "Timetable"


            }
        }
    }

代码:(PageViewController.swift)

import UIKit
import ChameleonFramework

class PageViewController: UIPageViewController,UIPageViewControllerDelegate {

    // created for use in the function which determines the title of the navigationBar
    var arrayIndex: Int = 0
    // reference for later function to determine title of navigationBar
    var pageControl = UIPageControl.self

    // NSUserDefaults
    let defaults = NSUserDefaults.standardUserDefaults()

    // set of viewControllers (based on their storyboard ID)

    private(set) lazy var orderedViewControllers: [UIViewController] = {
        return [self.newDayViewController("monday"),
                self.newDayViewController("tuesday"),
                self.newDayViewController("wednesday"),
                self.newDayViewController("thursday"),
                self.newDayViewController("friday"),
                self.newDayViewController("saturday"),
                self.newDayViewController("sunday")
        ]
    }()


    override func viewDidLoad() {
        super.viewDidLoad()


        self.setNeedsStatusBarAppearanceUpdate()
        // setting the datasource & Delegate of the UIPageViewController
        dataSource = self
        delegate = self



        // set the first viewController for the pageView (monday as it is the first in the set)

        if let firstViewController = orderedViewControllers.first {
            setViewControllers([firstViewController],
                               direction: .Forward,
                               animated: true,
                               completion: nil)


        }

    }





    // function to add view controllers
    // function will only instantiateViewControllers which have a storyboard id containing 'day' e.g Monday, Tuesday, Wednesday

    private func newDayViewController(day: String) -> UIViewController {
        return UIStoryboard(name: "Main", bundle: nil) .
            instantiateViewControllerWithIdentifier("\(day)")
    }




    // set the navigationBar title to the dayViewController's title
    // if the user is looking at orderedViewControllers[1], then the title of that day is "Tuesday"

    func pageViewController(pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
        if (!completed) {
            return
        }

        if let firstViewController = viewControllers?.first,
            let arrayIndex = orderedViewControllers.indexOf(firstViewController) {
            switch arrayIndex {
            case 0:
                self.navigationController!.navigationBar.topItem!.title = "Monday"
                break

            case 1:
                self.navigationController!.navigationBar.topItem!.title = "Tuesday"
                break

            case 2:
                self.navigationController!.navigationBar.topItem!.title = "Wednesday"
                break

            case 3:
                self.navigationController!.navigationBar.topItem!.title = "Thursday"

            case 4:
                self.navigationController!.navigationBar.topItem!.title = "Friday"
                break

            case 5:
                self.navigationController!.navigationBar.topItem!.title = "Saturday"
                break

            case 6:
                self.navigationController!.navigationBar.topItem!.title = "Sunday"
                break

            default:
                self.navigationController!.navigationBar.topItem!.title = "Timetable"


            }
        }
    }
}
// Mandatory functions and setup for the pageViewController to work

extension PageViewController: UIPageViewControllerDataSource {


    func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? {
        guard let viewControllerIndex = orderedViewControllers.indexOf(viewController) else {
            return nil
        }
        let previousIndex = viewControllerIndex - 1
        guard previousIndex >= 0 else {
            return orderedViewControllers.last
        }
        guard orderedViewControllers.count > previousIndex else {
            return nil
        }
        return orderedViewControllers[previousIndex]
    }

    func pageViewController(pageViewController: UIPageViewController,
                            viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {
        guard let viewControllerIndex = orderedViewControllers.indexOf(viewController) else {
            return nil
        }
        let nextIndex = viewControllerIndex + 1
        let orderedViewControllersCount = orderedViewControllers.count


        guard orderedViewControllersCount != nextIndex else {
            return orderedViewControllers.first
        }
        guard orderedViewControllersCount > nextIndex else {
            return nil
        }
        return orderedViewControllers[nextIndex]
    }
    // set number of viewControllers to be presented
    func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int {
        return orderedViewControllers.count
    }
    func presentationIndexForPageViewController(pageViewController: UIPageViewController) -> Int {
        guard let firstViewController = viewControllers?.first,
            firstViewControllerIndex = orderedViewControllers.indexOf(firstViewController) else {
                return 0
        }
        return firstViewControllerIndex
    }
}

Answer 1

在viewDidLoad()方法中添加

self.navigationItem.title

或

self.title