我对 UIPageViewController 有一个非常有趣的问题。
我的项目的设置与示例基于页面的应用程序模板非常相似。时不时（但在一定程度上可重现）某个平移手势会调用-(UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController.
我返回下一页的视图控制器，但从未运行过翻页动画，也从未调用过我的委托方法。
这是代码viewControllerAfterViewController
-(UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
PageDisplayViewController *vc = (PageDisplayViewController *)viewController;
NSUInteger index = [self.pageFetchController.fetchedObjects indexOfObject:vc.page];
if(index == (self.pageFetchController.fetchedObjects.count - 1)) return nil;
return [self getViewControllerForIndex:(++index)];
}
这里是getViewControllerForIndex:
-(PageDisplayViewController *)getViewControllerForIndex:(NSUInteger)index
{
PageDisplayViewController *newVC = [self.storyboard instantiateViewControllerWithIdentifier:@"PageDisplayController"];
newVC.page = [self.pageFetchController.fetchedObjects objectAtIndex:(index)];
newVC.view.frame = CGRectMake(0, 0, 1024, 604);
NSLog(@"%i", index);
if(index == 0)
{
//We're moving to the first, animate the back button to be hidden.
[UIView animateWithDuration:0.5 animations:^
{
self.backButton.alpha = 0.f;
} completion:^(BOOL finished){
self.backButton.hidden = YES;
}];
}
else if(index == (self.pageFetchController.fetchedObjects.count - 1))
{
[UIView animateWithDuration:0.5 animations:^{
self.nextButton.alpha = 0.f;
} completion:^(BOOL finished){
self.nextButton.hidden = YES;
}];
}
else
{
BOOL eitherIsHidden = self.nextButton.hidden || self.backButton.hidden;
if(eitherIsHidden)
{
[UIView animateWithDuration:0.5 animations:^{
if(self.nextButton.hidden)
{
self.nextButton.hidden = NO;
self.nextButton.alpha = 1.f;
}
if(self.backButton.hidden)
{
self.backButton.hidden = NO;
self.backButton.alpha = 1.f;
}
}];
}
}
return newVC;
}
基本上，我创建视图控制器，设置它的数据对象，然后根据索引淡出下一步/后退按钮。
委托方法
-(void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray *)previousViewControllers transitionCompleted:(BOOL)completed
{
PageDisplayViewController *vc = [previousViewControllers lastObject];
NSUInteger index = [self.pageFetchController.fetchedObjects indexOfObject:vc.page];
if (!completed)
{
[self.pagePreviewView setCurrentIndex:index];
NSLog(@"Animation Did not complete, reverting pagepreview");
}
else
{
PageDisplayViewController *curr = [pageViewController.viewControllers lastObject];
NSUInteger i = [self.pageFetchController.fetchedObjects indexOfObject:curr.page];
[self.pagePreviewView setCurrentIndex:i];
NSLog(@"Animation compeleted, updating pagepreview. Index: %u", i);
}
}
我只注意到这个问题，因为随机地，我的后退按钮会重新出现在屏幕上。在那里扔了一些NSLog()语句之后，我注意到我的 dataSource 方法被调用，索引为 1，但没有动画播放或委托被调用。更可怕的是，如果我尝试平移下一页，索引 1 会再次调用。
我担心这可能是 UIPageViewController 的错误。