需要滑动两次才能使页面视图控制器正常工作

Question

我正在构建应用，而我有一个UIPageViewController，其中包含2 UITableViewControllers。

这是VC头文件：

#import <UIKit/UIKit.h>

@interface EMPageViewController : UIViewController <UIPageViewControllerDataSource, UIPageViewControllerDelegate>

// init
-(id)initWithViewControllers:(NSArray<UIViewController*> *)viewControllers showDots:(BOOL)showDots pageSpacing:(CGFloat)pageSpacing frame:(CGRect)frame;

// Properties
@property (nonatomic, strong,readonly) UIPageViewController *pageViewController;
@property (nonatomic, strong, readonly) NSArray *navViewControllers;

@end

和实施文件：

#import "EMPageViewController.h"

@interface EMPageViewController ()

@property (nonatomic, strong, readwrite) UIPageViewController *pageViewController;
@property (nonatomic, strong, readwrite) NSArray *navViewControllers;

@end

@implementation EMPageViewController

-(id)initWithViewControllers:(NSArray<UIViewController*> *)viewControllers showDots:(BOOL)showDots pageSpacing:(CGFloat)pageSpacing frame:(CGRect)frame
{
    if (self = [super init])
    {
    /* init pageViewController */
    self.pageViewController = [[UIPageViewController alloc] initWithTransitionStyle:UIPageViewControllerTransitionStyleScroll navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal options:@{UIPageViewControllerOptionInterPageSpacingKey : [NSNumber numberWithFloat:pageSpacing]}];
    self.pageViewController.dataSource = self;
    self.pageViewController.delegate = self;
    self.pageViewController.view.frame = self.view.frame;
    [self.pageViewController willMoveToParentViewController:self];
    [self addChildViewController:self.pageViewController];
    [self.view addSubview:self.pageViewController.view];
    [self.pageViewController didMoveToParentViewController:self];


    if (!showDots)
    {
        /* remove dots */
        NSArray *subviews = self.pageViewController.view.subviews;
        UIPageControl *bottomControl = nil;
        for (int i=0; i<[subviews count]; i++) {
            if ([[subviews objectAtIndex:i] isKindOfClass:[UIPageControl class]]) {
                bottomControl = (UIPageControl *)[subviews objectAtIndex:i];
            }
        }
        bottomControl.hidden = true;
        self.pageViewController.view.frame = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height+40);
    }

    /* set viewcontrollers */
    self.navViewControllers = [NSArray arrayWithArray:viewControllers];

    [self.pageViewController setViewControllers:@[self.navViewControllers[0]] direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil];

    /* set other properties */
    self.view.frame = frame;
}
return self;
}

- (void)viewDidLoad {
[super viewDidLoad];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - page view controller data source

-(UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController
{
NSInteger currentIndex = [self.navViewControllers indexOfObject:viewController];
if (currentIndex != 0)
{
    return self.navViewControllers[currentIndex - 1];
} else
{
    return nil;
}
}

-(UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
NSInteger currentIndex = [self.navViewControllers indexOfObject:viewController];
if (currentIndex != ([self.navViewControllers count] - 1))
{
    return self.navViewControllers[currentIndex + 1];
} else
{
    return nil;
}
}

-(NSInteger)presentationCountForPageViewController:(UIPageViewController *)pageViewController
{
return self.navViewControllers.count;
}

-(NSInteger)presentationIndexForPageViewController:(UIPageViewController *)pageViewController
{
return 0;
}

此控制器来自另一个VC，如下所示：

PartyTableViewController *VC1 = [self.storyboard instantiateViewControllerWithIdentifier:@"FirstVC"];
MessagingViewController *VC2 = [[OtherVC new];
UINavigationController *NC2 = [[UINavigationController alloc] initWithRootViewController:VC2];

EMPageViewController *pageViewController = [[EMPageViewController alloc] initWithViewControllers:@[VC1, NC2] showDots:NO pageSpacing:3.0f frame:self.view.frame];

[self.navigationController pushViewController:pageViewController animated:YES];

会发生什么？

当显示页面VC时，我的第一根手指滑动不会做任何事情 - 但第二次完全滑动它。因此，只有其他所有滑动工作。

VC1和VC2都属于UITableViewController。

知道为什么吗？