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我一直在尝试让 UIScrollView 开始工作。到目前为止，它确实可以滚动，但不能滚动到我想要的 ViewController。而且我不知道该怎么做，所以这里的一些帮助会很好。

这就是ViewController.m的代码的样子

- (void)viewDidLoad {
    [super viewDidLoad];

    NSMutableArray *controllers = [[NSMutableArray alloc] init];

    [controllers addObject:[NSNull null]];
    [controllers addObject:[NSNull null]];

    self.viewControllers = controllers;

    self.scrollView.pagingEnabled = YES;
    self.scrollView.contentSize =
    CGSizeMake(CGRectGetWidth(self.scrollView.frame) * 2, CGRectGetHeight(self.scrollView.frame));
    self.scrollView.showsHorizontalScrollIndicator = YES;
    self.scrollView.delegate = self;

    self.pageControl.numberOfPages = 2;
    self.pageControl.currentPage = 0;

    [self loadScrollViewWithPage:0];
    [self loadScrollViewWithPage:1];

    // Do any additional setup after loading the view.
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)loadScrollViewWithPage:(NSUInteger)page
{
    if (page >= 2)
        return;

    // replace the placeholder if necessary
    ViewController2 *controller = [self.viewControllers objectAtIndex:page];
    if ((NSNull *)controller == [NSNull null])
    {
        controller = [[ViewController2 alloc] init];
        [self.viewControllers replaceObjectAtIndex:page withObject:controller];
    }

    // add the controller's view to the scroll view
    if (controller.view.superview == nil)
    {
        CGRect frame = self.scrollView.frame;
        frame.origin.x = CGRectGetWidth(frame) * page;
        frame.origin.y = 0;
        controller.view.frame = frame;

        [self addChildViewController:controller];
        [self.scrollView addSubview:controller.view];
        [controller didMoveToParentViewController:self];
    }
}

// at the end of scroll animation, reset the boolean used when scrolls originate from the UIPageControl
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    // switch the indicator when more than 50% of the previous/next page is visible
    CGFloat pageWidth = CGRectGetWidth(self.scrollView.frame);
    NSUInteger page = floor((self.scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
    self.pageControl.currentPage = page;

    // load the visible page and the page on either side of it (to avoid flashes when the user starts scrolling)
    [self loadScrollViewWithPage:page - 1];
    [self loadScrollViewWithPage:page];
    [self loadScrollViewWithPage:page + 1];

    // a possible optimization would be to unload the views+controllers which are no longer visible
}

- (void)gotoPage:(BOOL)animated
{
    NSInteger page = self.pageControl.currentPage;

    // load the visible page and the page on either side of it (to avoid flashes when the user starts scrolling)
    [self loadScrollViewWithPage:page - 1];
    [self loadScrollViewWithPage:page];
    [self loadScrollViewWithPage:page + 1];

    // update the scroll view to the appropriate page
    CGRect bounds = self.scrollView.bounds;
    bounds.origin.x = CGRectGetWidth(bounds) * page;
    bounds.origin.y = 0;
    [self.scrollView scrollRectToVisible:bounds animated:animated];
}

- (IBAction)changePage:(id)sender
{
    [self gotoPage:YES];    // YES = animate
}

所以会发生什么是第一个视图被加载。我可以滚动，但它滚动到一个空视图。我想做的是它滚动到ViewController2

我该如何实现它呢？（水平）

EDIT1，试图实现马特建议的

- (void)viewDidLoad {
    [super viewDidLoad];

    self.vcIdentifiers = @[@"PageContentViewController", @"PageContentViewController1"];

    // Create page view controller
    self.pageViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"PageViewController"];
    self.pageViewController.dataSource = self;

    UIViewController *startingViewController = [self viewControllerAtIndex:0];
    NSArray *viewControllers = @[startingViewController];
    [self.pageViewController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil];

    self.pageViewController.view.frame = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height - 30);

    [self addChildViewController:_pageViewController];
    [self.view addSubview:_pageViewController.view];
    [self.pageViewController didMoveToParentViewController:self];

}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (PageContentViewController *)viewControllerAtIndex:(NSUInteger)index
{
    if (([self.vcIdentifiers count] == 0) || (index >= self.vcIdentifiers.count)) {
        return nil;
    }


    // Create a new view controller and pass suitable data.
    PageContentViewController *pageContentViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"PageContentViewController"];
    pageContentViewController.titleText = self.pageTitles[index];
    pageContentViewController.pageIndex = index;

    return pageContentViewController;
}


- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController
{
    NSUInteger index = ((PageContentViewController*) viewController).pageIndex;

    if ((index == 0) || (index == NSNotFound)) {
        return nil;
    }

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

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
    NSUInteger index = ((PageContentViewController*) viewController).pageIndex;

    if (index == NSNotFound) {
        return nil;
    }

    index++;
    if (index == [self.pageTitles count]) {
        return nil;
    }
    return [self viewControllerAtIndex:index];
}

- (NSInteger)presentationCountForPageViewController:(UIPageViewController *)pageViewController
{
    //return [self.pageTitles count];
    return 2;
}

- (NSInteger)presentationIndexForPageViewController:(UIPageViewController *)pageViewController
{
    return 0;
}

我正在考虑使用我的视图控制器拥有的情节提要 id，它们位于 VCidentifiers 中。

我不明白的是如何在viewControllerAtIndex方法中实例化视图控制器。现在的写法，它只会创建PageContentViewController，当它应该为索引0创建PageContentViewController和为索引1创建PageContent2Controller时。

我错过了什么？

4

1 回答 1

1

滚动视图用于在现有视图之间滚动，而不是用于从视图控制器动态加载视图。您可以以这种方式使用视图控制器，我们过去有时必须这样做，但是（正如您所发现的）这很困难。

我建议您放弃滚动视图并以滚动样式使用 UIPageViewController。当您想要在视图控制器的视图之间滚动时，它为您解决了所有问题。

于 2015-04-18T15:09:09.883 回答