Question

我正在尝试实施UIPageViewController。我创建了4个单独的viewControllers并添加到我的故事板中。现在我想用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，我得到以下错误。

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

任何人都可以帮我这个吗？

亲切的问候.. 的修改

 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，如果找不到该对象，则-[NSArray indexOfObject:]返回。

所以在你的行

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

viewController不在modelArray中。这是因为您每次都在创建视图控制器的新实例。

在旁注中，您正在执行self.modelArray = [[NSMutableArray alloc] init];，然后对该数组执行任何操作，并在self.modelArray = pageData;时将其丢弃。当你刚刚使用一个时，无需在那里创建两个空数组。

Answer 2

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

在这里，您将创建ViewOneViewController的新对象，并添加到pageViewController的viewControllers数组中。此cVC对象与之前在modelArray中添加的对象无关。这两者都是同一类的不同对象，即ViewOneViewController。

因此，您必须将相同的对象从modelArray传递给pageViewController的viewControllers数组，以便在执行时不会获得垃圾值

NSUInteger currentIndex = [self.modelArray indexOfObject:viewController]; //will return garbage value in your case

讨论instantiateViewControllerWithIdentifier:

此方法创建指定视图控制器的新实例每次你打电话。

Answer 3

在调用方法indexOfObject:之后，您应该验证返回的索引是否为NSNotFound，返回的值是对象不在数组中。

你的代码看起来应该更像这样;

NSUInteger currentIndex = [self.modelArray indexOfObject:viewController];
if(currentIndex == NSNotFound ||
   currentIndex == self.modelArray.count - 1)
    return nil;

将来，您应该可以使用Xcode exception breakpoint。

自行查找此错误

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

3 个答案: