ios - PageviewController 总是返回一个像 2147483648 这样的索引

Question

我正在尝试实现一个 UIPageViewController。我创建了 4 个单独的 viewControllers 并将其添加到我的 Storyboard 中。现在我想使用 UIPageViewController 滚动它。这就是我在代码中所做的。

我制作了一个 modelArray 并将所有 VC 放入其中:

   self.modelArray = [[NSMutableArray alloc] init];
   NSMutableArray *pageData = [[NSMutableArray alloc]init];
    ViewOneViewController *viewOne = [self.storyboard instantiateViewControllerWithIdentifier:@"ViewOne"];
    ViewTwoViewController *viewTwo = [self.storyboard instantiateViewControllerWithIdentifier:@"ViewTwo"];
    ViewThreeViewController *viewThree = [self.storyboard instantiateViewControllerWithIdentifier:@"ViewThree"];
    ViewFourViewController *viewFour = [self.storyboard instantiateViewControllerWithIdentifier:@"ViewFour"];

    [pageData addObject:viewOne];
    [pageData addObject:viewTwo];
    [pageData addObject:viewThree];
    [pageData addObject:viewFour];

    self.modelArray = pageData;

接下来设置 UIPageViewController 的基础知识并设置初始 VC:

 ViewOneViewController *cVC = [self.storyboard instantiateViewControllerWithIdentifier:@"ViewOne"];
    NSArray *viewControllers = [NSArray arrayWithObject:cVC];
    [self.pageViewController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil];

    // Add the pageViewController as the childViewController
    [self addChildViewController:self.pageViewController];

    // Add the view of pageViewController  to the currentView
    [self.view addSubview:self.pageViewController.view];

    // Call didMoveToParentViewController: of the childViewController, the UIPageViewController instance in our case.
    [self.pageViewController didMoveToParentViewController:self];

    // Assign the gestureRecognizers property of the pageViewController to the view's gestureRecognizers property
    self.view.gestureRecognizers = self.pageViewController.gestureRecognizers;

最后这些是我的委托(delegate)方法(例如下一个VC的方法)

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController
       viewControllerAfterViewController:(UIViewController *)viewController
{
    NSUInteger currentIndex = [self.modelArray indexOfObject:viewController];
    if(currentIndex == self.modelArray.count - 1)
        return nil;

    UIViewController *cVC = [self.modelArray objectAtIndex:currentIndex + 1];
    return cVC;
}

但是当我构建并运行时，出现以下错误。

Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 2147483648 beyond bounds [0 .. 3]'

谁能帮我解决这个问题？

亲切的问候..编辑

 thread #1: tid = 0x2403, 0x37776350 libsystem_kernel.dylib`__pthread_kill + 8, stop reason = signal SIGABRT
    frame #0: 0x37776350 libsystem_kernel.dylib`__pthread_kill + 8
    frame #1: 0x33115122 libsystem_c.dylib`pthread_kill + 58
    frame #2: 0x33151972 libsystem_c.dylib`abort + 94
    frame #3: 0x36f2fd4e libc++abi.dylib`abort_message + 74
    frame #4: 0x36f2cff8 libc++abi.dylib`default_terminate() + 24
    frame #5: 0x3165ba76 libobjc.A.dylib`_objc_terminate() + 146
    frame #6: 0x36f2d07a libc++abi.dylib`safe_handler_caller(void (*)()) + 78
    frame #7: 0x36f2d114 libc++abi.dylib`std::terminate() + 20
    frame #8: 0x36f2e598 libc++abi.dylib`__cxa_rethrow + 88
    frame #9: 0x3165b9d0 libobjc.A.dylib`objc_exception_rethrow + 12
    frame #10: 0x38c82f20 CoreFoundation`CFRunLoopRunSpecific + 456
    frame #11: 0x38c82d48 CoreFoundation`CFRunLoopRunInMode + 104
    frame #12: 0x34bbc2ea GraphicsServices`GSEventRunModal + 74
    frame #13: 0x35c14300 UIKit`UIApplicationMain + 1120
    frame #14: 0x0005050c Franke2`main(argc=1, argv=0x2fdb1d20) + 116 at main.m:16
    frame #15: 0x340ccb20 libdyld.dylib`start + 4

Answer 1

2147483648 是 NSNotFound，这是 -[NSArray indexOfObject:] 在找不到对象时返回的内容。

所以在你的行中

    NSUInteger currentIndex = [self.modelArray indexOfObject:viewController];

viewController 不在 modelArray 中。这是因为您每次都在创建 View Controller 的新实例。

旁注，你在做 self.modelArray = [[NSMutableArray alloc] init]; 然后什么都不做，当你 self.modelArray 时把它扔掉= 页面数据；。当您只使用一个时，无需在那里创建两个空数组。