UIPageViewController in iOS6

Question

在方法viewControllerAfterViewController和viewControllerBeforeViewController中的iOS6中，如果返回nil (在第一页或最后一页时阻止页面导航)，则应用程序崩溃，但有此例外：

“提供的视图控制器数量(0)与所请求的转换所需的数量(1)不匹配”

在iOS5中，一切都很好。

Answer 1

我也有过同样的问题。我发现原因是取代了UIPanGestureRecognizer of UIPageViewController的代表，这是不-不是的。pan手势识别器调用了_gestureRecognizerShouldBegin：(注意前面的下划线)方法，UIPageViewController实现了该方法，并且显然依赖于正确工作(读:不崩溃)。最后，我实现了respondsToSelector:和forwardingTargetForSelector:在我的类中，它使用UIPageViewController将无文档的委托方法传递给UIPageViewController，而没有具体地命名它(几乎可以肯定，这给我带来了应用程序商店的审查拒绝)。

-(BOOL)respondsToSelector:(SEL)aSelector {
    if ([super respondsToSelector:aSelector])
        return YES;
    else if ([self.pageViewController respondsToSelector:aSelector])
        return YES;
    else
        return NO;
}

- (id)forwardingTargetForSelector:(SEL)aSelector {
    if ([super respondsToSelector:aSelector]) {
        return nil;
    } else if ([self.pageViewController respondsToSelector:aSelector]) {
        return self.pageViewController;
    }
    return nil;
}

我的长期解决方案将是重新使用UIPageViewController，这样我就不需要替换手势识别器委托。

Answer 2

啊，我想知道为什么没有人指出这个问题，我花了将近两个晚上才找到解决办法。

旧代码( iOS 5.1)：当在第一页和最后一页返回零时，您将体验到应用程序crash.It在iOS 5.1中工作得很好，但在iOS 6中却不会。

- (UIViewController *)pageViewController:
(UIPageViewController *)pageViewController viewControllerBeforeViewController:
(UIViewController *)viewController
{
    for (UIGestureRecognizer *recognizer in pageController.gestureRecognizers) {
        if ([recognizer isKindOfClass:[UITapGestureRecognizer class]]) {
            recognizer.enabled = NO;
        }
    }
    NSUInteger index = [self indexOfViewController:
                        (MainViewController *)viewController];
    if ((index == 0) || (index == NSNotFound)) {
        return nil;
    }

    index--;
    return [self viewControllerAtIndex:index];
}
- (UIViewController *)pageViewController:
(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
    for (UIGestureRecognizer *recognizer in pageController.gestureRecognizers) {
        if ([recognizer isKindOfClass:[UITapGestureRecognizer class]]) {
            recognizer.enabled = NO;
        }
    }
    NSUInteger index = [self indexOfViewController:
                        (MainViewController *)viewController];
    if (index == NSNotFound) {
        return nil;
    }
}

解决方案( -(BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer 6)：在将手势效果添加到superview之后，只需调用名为iOS*的委托gestureRecognizer即可。我所做的是安静而简单的，计算用户翻转第一页和最后一页的速度(我指的是使用手势识别器)，我否认您需要做的swiping.All只是粘贴以下代码，您就完成了！

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
    if (pageNum==0) {

        if ([(UIPanGestureRecognizer*)gestureRecognizer isKindOfClass:[UIPanGestureRecognizer class]] &&
            [(UIPanGestureRecognizer*)gestureRecognizer velocityInView:gestureRecognizer.view].x > 0.0f) {
            //NSLog(@"Swiping to left on 1st page is denied");
            return NO;
        }
        if ([(UITapGestureRecognizer*)gestureRecognizer isKindOfClass:[UITapGestureRecognizer class]] &&
            [(UITapGestureRecognizer*)gestureRecognizer locationInView:gestureRecognizer.view].x < self.view.frame.size.width/2) {
         //NSLog(@"tapping to left on 1st page is denied");
            return NO;
        }
    }

    else if(pageNum ==totalNoOfFiles-1)
    {

        if ([(UIPanGestureRecognizer*)gestureRecognizer isKindOfClass:[UIPanGestureRecognizer class]] &&
            [(UIPanGestureRecognizer*)gestureRecognizer velocityInView:gestureRecognizer.view].x < 0.0f) {
            //NSLog(@"Swiping to right on 1st page is denied");
            return NO;
        }
        if ([(UITapGestureRecognizer*)gestureRecognizer isKindOfClass:[UITapGestureRecognizer class]] &&
            [(UITapGestureRecognizer*)gestureRecognizer locationInView:gestureRecognizer.view].x > self.view.frame.size.width/2) {
          //NSLog(@"Tapping to right on 1st page is denied");
            return NO;
        }
    }

    return YES;
}


- (UIViewController *)pageViewController:(UIPageViewController*) pageViewController viewControllerBeforeViewController:(UIViewController *)viewController
 {
  int index = [self indexOfViewController:(ChildViewController *)viewController];
                index--;

    return [self viewControllerAtIndex:index];
}


- (UIViewController *)pageViewController:
(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
    int index = [self indexOfViewController:(ChildViewController *)viewController];

            index++;
     return [self viewControllerAtIndex:index];
}

Answer 3

这一点已经讨论过了，但我有一件事要补充。请考虑为什么要将手势识别器的委托设置为self。在我的例子中，这是因为在某些情况下，我想防止手势识别器与委托的gestureRecognizerShouldBegin:识别。

但是在出现这个问题的iOS 6中，通过在gestureRecognizerShouldBegin:上实现UIView，有一种全新的方法可以做到这一点。(这是UIView 6中的一个新的iOS实例方法。)

因此，我能够完全完成我以前所做的事情，而不改变手势识别器的代表。