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如何将UIPageControl作为 UIViewController的容器 已翻译 100%

彭博 投递于 2012/11/27 10:57 (共 6 段, 翻译完成于 11-27)
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Objective-C
英文原文：Using UIPageControl as a container UIViewController
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参与翻译 (1人) : 彭博

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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。
彭博
彭博
翻译于 2012/11/27 10:57
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1
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。
彭博
彭博
翻译于 2012/11/27 10:58
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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];
    }
}

彭博
彭博
翻译于 2012/11/27 11:01
顶
1
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;
        }
}
彭博
彭博
翻译于 2012/11/27 11:03
顶
1
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];
}

彭博
彭博
翻译于 2012/11/27 11:05
顶
1
总结
废话少说，这里放出代码，在 GitHub上
彭博
彭博
翻译于 2012/11/27 11:05
顶
1
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