如何将UIPageControl作为 UIViewController的容器
jopen
12年前
虽然看上去用 UIPageControl 在一系列 UIView或UIViewController中导航是很平常的事情，但实际上 Apple公司并没有提供一个这样的方法或者演示Demo:
在最新的iOS版本中(5.0 现在已经不是最新的)，Apple公司提供了很多如何用其他方式实现
UIViewController容器的方式(可以从这里参考)，但悲剧的是它们与 UIPageControl 没多大关系。
那么我们今天就来专门解决这个问题。
创建界面
首先我们需要在 Interface Builder 中在一个UIViewController里面创建一个UIPageControl与UIScrollView。当然你可以创建很多类似的UIViewController。
设置 PageViewController 类
这里的 PageViewController 对象将包含一个 UIScrollView 与一个 UIPageControl。而且 UIScrollView 将会包含所有的 subview, 这些subview就是被UIPageControl控制的子页面。
你也许会在 viewController 中添加一些算法来专门处理页面转换: addChildViewController:方法。然而在我这个案例中却不是这么做的，来一起看看代码：
@interface PagerViewController : UIViewController @property (nonatomic, strong) IBOutlet UIScrollView *scrollView; @property (nonatomic, strong) IBOutlet UIPageControl *pageControl; - (IBAction)changePage:(id)sender; @end
在实现的代码文件中，首先我先不让它能够旋转屏幕。然后当 PagerViewController 预备显示时，我们需要标记一下当前哪一个view是被激活的，即被显示的，那么需要在 viewDidApplear 以及 viewWillDisappear方法中加入以下代码：
- (BOOL)automaticallyForwardAppearanceAndRotationMethodsToChildViewControllers { return NO; } - (void)viewDidAppear:(BOOL)animated { [super viewDidAppear:animated]; UIViewController *viewController = [self.childViewControllers objectAtIndex:self.pageControl.currentPage]; if (viewController.view.superview != nil) { [viewController viewDidAppear:animated]; } } - (void)viewWillDisappear:(BOOL)animated { UIViewController *viewController = [self.childViewControllers objectAtIndex:self.pageControl.currentPage]; if (viewController.view.superview != nil) { [viewController viewWillDisappear:animated]; } [super viewWillDisappear:animated]; } - (void)viewDidDisappear:(BOOL)animated { UIViewController *viewController = [self.childViewControllers objectAtIndex:self.pageControl.currentPage]; if (viewController.view.superview != nil) { [viewController viewDidDisappear:animated]; } [super viewDidDisappear:animated]; } viewWillAppear 可能会有点复杂，因为我们也需要加载所有的子view到 scrollView中，而且必须确保scrollview的contentsize比子view要大。
- (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; for (NSUInteger i =0; i < [self.childViewControllers count]; i++) { [self loadScrollViewWithPage:i]; } self.pageControl.currentPage = 0; _page = 0; [self.pageControl setNumberOfPages:[self.childViewControllers count]]; UIViewController *viewController = [self.childViewControllers objectAtIndex:self.pageControl.currentPage]; if (viewController.view.superview != nil) { [viewController viewWillAppear:animated]; } self.scrollView.contentSize = CGSizeMake(scrollView.frame.size.width * [self.childViewControllers count], scrollView.frame.size.height); } 为了将UIViewController的内容加载到UIScrolView的contentView中，需要如下代码:
- (void)loadScrollViewWithPage:(int)page { if (page < 0) return; if (page >= [self.childViewControllers count]) return; // replace the placeholder if necessary UIViewController *controller = [self.childViewControllers objectAtIndex:page]; if (controller == nil) { return; } // add the controller's view to the scroll view if (controller.view.superview == nil) { CGRect frame = self.scrollView.frame; frame.origin.x = frame.size.width * page; frame.origin.y = 0; controller.view.frame = frame; [self.scrollView addSubview:controller.view]; } } 处理滚动
为了处理滚动，我们需要实现几个 UIScrollViewDelegate 的方法以及尽早声明方法 - (IBAction)changePage:(id)sender
首先必须先知道滚动是如何实现的，要么是手势，要么就是点击了 UIPageControl 的一侧。
来一起看看下面的代码：
// At the begin of scroll dragging, reset the boolean used when scrolls originate from the UIPageControl - (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView { _pageControlUsed = NO; } // At the end of scroll animation, reset the boolean used when scrolls originate from the UIPageControl - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView { _pageControlUsed = NO; } - (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView { UIViewController *oldViewController = [self.childViewControllers objectAtIndex:_page]; UIViewController *newViewController = [self.childViewControllers objectAtIndex:self.pageControl.currentPage]; [oldViewController viewDidDisappear:YES]; [newViewController viewDidAppear:YES]; _page = self.pageControl.currentPage; } 现在，为了当页面改变时也能更新当前的显示，我们只需要实现 scrollViewDidScroll delegate方法以及 changePage IBAction 方法。
- (IBAction)changePage:(id)sender { int page = ((UIPageControl *)sender).currentPage; // update the scroll view to the appropriate page CGRect frame = self.scrollView.frame; frame.origin.x = frame.size.width * page; frame.origin.y = 0; UIViewController *oldViewController = [self.childViewControllers objectAtIndex:_page]; UIViewController *newViewController = [self.childViewControllers objectAtIndex:self.pageControl.currentPage]; [oldViewController viewWillDisappear:YES]; [newViewController viewWillAppear:YES]; [self.scrollView scrollRectToVisible:frame animated:YES]; // Set the boolean used when scrolls originate from the UIPageControl. See scrollViewDidScroll: above. _pageControlUsed = YES; } - (void)scrollViewDidScroll:(UIScrollView *)sender { // We don't want a "feedback loop" between the UIPageControl and the scroll delegate in // which a scroll event generated from the user hitting the page control triggers updates from // the delegate method. We use a boolean to disable the delegate logic when the page control is used. if (_pageControlUsed || _rotating) { // do nothing - the scroll was initiated from the page control, not the user dragging return; } // Switch the indicator when more than 50% of the previous/next page is visible CGFloat pageWidth = self.scrollView.frame.size.width; int page = floor((self.scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1; if (self.pageControl.currentPage != page) { UIViewController *oldViewController = [self.childViewControllers objectAtIndex:self.pageControl.currentPage]; UIViewController *newViewController = [self.childViewControllers objectAtIndex:page]; [oldViewController viewWillDisappear:YES]; [newViewController viewWillAppear:YES]; self.pageControl.currentPage = page; [oldViewController viewDidDisappear:YES]; [newViewController viewDidAppear:YES]; _page = page; } } 最后处理旋转
首先在shouldAutorotateToInterfaceOrientation方法中返回 YES，同时也需要传输一下3个消息给当前被显示的子 UIViewController。
willAnimateRotationToInterfaceOrientation:duration:
willRotateToInterfaceOrientation:duration:
didRotateFromInterfaceOrientation:
但我们还是要自己处理旋转的问题，比如要重新缩放scrollview的contentView，以及调整子view的帧率，否则会出现一些无法预料的事情。所以来看看以下处理方式
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { return YES; } - (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration { UIViewController *viewController = [self.childViewControllers objectAtIndex:self.pageControl.currentPage]; [viewController willRotateToInterfaceOrientation:toInterfaceOrientation duration:duration]; _rotating = YES; } - (void)willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration { UIViewController *viewController = [self.childViewControllers objectAtIndex:self.pageControl.currentPage]; [viewController willAnimateRotationToInterfaceOrientation:toInterfaceOrientation duration:duration]; self.scrollView.contentSize = CGSizeMake(scrollView.frame.size.width * [self.childViewControllers count], scrollView.frame.size.height); NSUInteger page = 0; for (viewController in self.childViewControllers) { CGRect frame = self.scrollView.frame; frame.origin.x = frame.size.width * page; frame.origin.y = 0; viewController.view.frame = frame; page++; } CGRect frame = self.scrollView.frame; frame.origin.x = frame.size.width * _page; frame.origin.y = 0; [self.scrollView scrollRectToVisible:frame animated:NO]; } - (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation { _rotating = NO; UIViewController *viewController = [self.childViewControllers objectAtIndex:self.pageControl.currentPage]; [viewController didRotateFromInterfaceOrientation:fromInterfaceOrientation]; } 总结