Question

我有一个UIPageViewController PageVC，其中包含我在故事板中创建的6个视图控制器。我的PageVC课程是用Swift编写的。

class PageVC: UIPageViewController, UIPageViewControllerDelegate {

    lazy var VCArr: [UIViewController] = {
        return [self.VCInstance(name: "OB1"),
                self.VCInstance(name: "OB2"),
                self.VCInstance(name: "OB3"),
                self.VCInstance(name: "OB4"),
                self.VCInstance(name: "OB5"),
                self.VCInstance(name: "OB6")]
    }()

    private func VCInstance(name: String) -> UIViewController {
        return UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: name)

    }

    override public func viewDidLoad() {
        super.viewDidLoad()

        self.delegate = self
        if let OB1 = VCArr.first {
            setViewControllers([OB1], direction: .forward, animated: true, completion: nil)

        }
    }

    public func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController?{
        guard let viewControllerIndex = VCArr.index(of: viewController) else {
            return nil
        }

        let previousIndex = viewControllerIndex - 1

        guard previousIndex >= 0 else {
            return VCArr.last
        }

        guard VCArr.count > previousIndex else {
            return nil
        }

        return VCArr[previousIndex]
    }

    public func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController?{
        guard let viewControllerIndex = VCArr.index(of: viewController) else {
            return nil
        }

        let nextIndex = viewControllerIndex + 1

        guard nextIndex < VCArr.count else {
            return VCArr.first
        }

        guard VCArr.count > nextIndex else {
            return nil
        }

        return VCArr[nextIndex]
    }

    public func presentationCount(for pageViewController: UIPageViewController) -> Int{

        return VCArr.count

        }

    public func presentationIndex(for pageViewController: UIPageViewController) -> Int{

        guard let OB1 = viewControllers?.first,
            let OB1Index = VCArr.index(of: OB1) else {
                return 0

        }

        return OB1Index
    }

    public func nextPageWithIndex(index: Int)
    {
        let nextVC = VCArr[index]
        setViewControllers([nextVC], direction: .forward, animated: true, completion: nil)

    }


}

在每个包含的视图控制器中，我有按钮前进到下一个PageVC索引。大多数包含的视图控制器都有用Objective-C编写的类，所以我调用了下一页的方法：

-(void)pageNext {

    PageVC *vc = (PageVC *) self.parentViewController;
    [vc nextPageWithIndexWithIndex:2];

}

上述转换效果很好，OB3完全加载。在OB3我有一个IBOutlet到一个按钮，它显示我的通知权限对话框，我的下一页方法在完成处理程序中调用，如下所示。

- (IBAction)enableBtn:(id)sender {

    UNUserNotificationCenter* center = [UNUserNotificationCenter currentNotificationCenter];
    [center requestAuthorizationWithOptions:(UNAuthorizationOptionAlert + UNAuthorizationOptionSound)
                          completionHandler:^(BOOL granted, NSError * _Nullable error) {

                              [self pageNext];

                              [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"notification"];

                              [[NSUserDefaults standardUserDefaults] synchronize];

                              FIRUser *user = [[FIRAuth auth] currentUser];
                              NSString *topic = [@"/topics/ios_user_" stringByAppendingString:user.uid];
                              [[FIRMessaging messaging] subscribeToTopic:topic];

                          }];

    [[UIApplication sharedApplication] registerForRemoteNotifications];

}

点击＆＃34;允许＆＃34;页面顺利过渡在通知权限对话框中，OB4上的某些元素在转换发生后几乎没有加载10秒。例如，按钮出现但文本内部不可见，UILabels也不可见。如果我等待大约10秒钟，他们会出现。我已尝试重新排列PageVC索引中的页面，但无论我使用哪个页面，该页面始终显示为部分加载。没有正确加载的元素附加动画。我认为它与权限对话框中的完成处理程序有关。如何在转换时完全加载UIPageViewController加载中的下一页？

Answer 1

听起来您正在从非主线程更新UI。尝试将[self pageNext]放入主队列中的调度：

dispatch_async(dispatch_get_main_queue(), ^{ //update UI in main thread.
    [self pageNext]
});

我的UIPageViewController中的下一页仅在页面更改时部分加载

1 个答案: