Question

我有一个应用程序，其中包含一个包含多个tableviews的scrollview。每个tableview都从另一个viewcontroller加载。它是从Apple的PageControl示例应用程序构建的。我的目标是让它像Apple的天气应用程序一样工作。

我把一切都运转得很好。所有内容都完美加载，并且左右滚动显示所有正确的tableviews及其相关数据。我有一个按钮，当点击它时会打开另一个视图，允许您编辑每个项目，就像天气应用程序一样，您可以添加新城市，删除它或移动它。

我遇到的问题是当用户完成编辑项目时如何更新滚动视图。想象一下，PageControl应用程序能够删除第5页或将第4页移动到位置＃1等。

我没有粘贴任何代码，因为：1）它与PageControl应用程序中的代码相同; 2）我还没弄明白从哪里开始。希望有人可以帮助我。

感谢。

更新：（2010年3月5日美国东部时间上午3:18）

好的，所以我一直在研究这个问题。我能够在mainView中调用一个方法来更新scrollView。代码似乎有点笨重，但它的工作原理！我真的不喜欢这些代码，因为我最终使用了一次属性，而我无法再次设置它，因为我收到错误objc[10801]: FREED(id): message release sent to freed object=0x3f4a490。对我来说，似乎对象已被释放？如果是这样，我不知道如何，因为我只在dealloc中发布它。永远不会调用dealloc（我会检查NSLog）所以我不知道发生了什么。

代码：初始代码与Apple的PageControl示例应用程序中的代码相同：

- (void)viewDidLoad {
    [super viewDidLoad];
    appDel = (iBarryAppDelegate *)[[UIApplication sharedApplication] delegate];
    managedObjectContext = appDel.managedObjectContext;
    NSMutableArray *controllers = [[NSMutableArray alloc] init];
    for (unsigned i = 0; i < numberOfPages; i++)
    {
        [controllers addObject:[NSNull null]];
    }
    self.viewControllers = controllers;
    [controllers release];
    scrollView.pagingEnabled = YES;
    scrollView.contentSize = CGSizeMake(scrollView.frame.size.width * numberOfPages, scrollView.frame.size.height);
    scrollView.showsHorizontalScrollIndicator = NO;
    scrollView.showsVerticalScrollIndicator = NO;
    scrollView.scrollsToTop = NO;
    scrollView.delegate = self;
    pageControl.numberOfPages = numberOfPages;
    pageControl.currentPage = 0;
    //I end up commenting out all the method calls to
    //[self loadScrollViewWithPage:xxx]; and load all the views at once.
    //I know I should be lazy-loading here , but Scrolling is much 
    //faster if I load them all at once, instead 
    //of when they are about to be viewed.
    for (unsigned i = 0; i < numberOfPages; i++)
    {
        [self loadScrollViewWithPage:i];
    }
}
- (void)loadMainController:(int)page
{
    MainViewController *controller = [viewControllers objectAtIndex:page];
    if ((NSNull *)controller == [NSNull null])
    {
        controller = [[MainViewController alloc] initWithPageNumber:page];
        [viewControllers replaceObjectAtIndex:page withObject:controller];
        [controller release];
    }
    if (nil == controller.view.superview)
    {
        CGRect frame = scrollView.frame;
        frame.origin.x = frame.size.width * page;
        frame.origin.y = 0;
        controller.view.frame = frame;
        [scrollView addSubview:controller.view];
    }
}
- (void)loadScrollViewWithPage:(int)page
{
    if (page < 0) return;
    if (page >= numberOfPages) return;
    [self loadMainController:page];
}
- (void)scrollViewDidScroll:(UIScrollView *)sender
{
    if (pageControlUsed)
    {
        return;
    }
    CGFloat pageWidth = scrollView.frame.size.width;
    int page = floor((scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
    pageControl.currentPage = page;
//  [self loadScrollViewWithPage:page - 1];
//  [self loadScrollViewWithPage:page];
//  [self loadScrollViewWithPage:page + 1];
}
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    pageControlUsed = NO;
}
- (IBAction)changePage:(id)sender
{
    int page = pageControl.currentPage;
//  [self loadScrollViewWithPage:page - 1];
//  [self loadScrollViewWithPage:page];
//  [self loadScrollViewWithPage:page + 1];
    CGRect frame = scrollView.frame;
    frame.origin.x = frame.size.width * page;
    frame.origin.y = 0;
    [scrollView scrollRectToVisible:frame animated:YES];
    pageControlUsed = YES;
}

然后我将代码添加到刷新 scrollView。我所做的是删除所有子视图并重新加载它们。我不会有超过13个子视图，不确定是否删除它们并重新创建它们是一个好主意或坏主意。

- (void)reloadDataNow
{
    for(UIView *subview in [scrollView subviews]) {
            [subview removeFromSuperview];
            NSLog(@"removed a suview");
    }
    [self loadData]; //this method fetches which data will be 
    //in the scrollView. It reloads the number of pages based 
    //on the return result and an NSMutableArray where I store 
    //data to pass to the views that will appear in the scrollView
    NSMutableArray *controllers = [[NSMutableArray alloc] init];
    for (unsigned i = 0; i < numberOfPages; i++)
    {
        [controllers addObject:[NSNull null]];
    }
    scrollView.pagingEnabled = YES;
    scrollView.contentSize = CGSizeMake(scrollView.frame.size.width * numberOfPages, scrollView.frame.size.height);
    scrollView.showsHorizontalScrollIndicator = NO;
    scrollView.showsVerticalScrollIndicator = NO;
    scrollView.scrollsToTop = NO;
    scrollView.delegate = self;
    pageControl.numberOfPages = numberOfPages;
    pageControl.currentPage = 0;
    for (unsigned i = 0; i < numberOfPages; i++)
    {
        MainViewController *controller = [controllers objectAtIndex:i];
        if ((NSNull *)controller == [NSNull null])
        {
            controller = [[MainViewController alloc] initWithPageNumber:i team:[[favoritesArray objectAtIndex:i] teamR]];
            [controllers replaceObjectAtIndex:i withObject:controller];
            [controller release];
        }
        if (nil == controller.view.superview)
        {
            CGRect frame = scrollView.frame;
            frame.origin.x = frame.size.width * i;
            frame.origin.y = 0;
            controller.view.frame = frame;
            [scrollView addSubview:controller.view];
        }
    }
    //********************CRASH******************
    //Ideally, I think, the line below would replace the contents of
    //viewControllers with the new controllers. Here is where I get the 
    //"objc[10801]: FREED(id): message release sent to freed object=0x3f4a490" 
    //error. This line should probably be placed after [self loadData] or something,
    //but it crashes so I put but here to display better. I tried
    //adding self.viewControllers = nil; but I don't think that is 
    //the problem with the error message.
    self.viewControllers = controllers;
}

从子视图调用reloadDataNow方法，可以添加或删除要在scrollView上显示的项。

Answer 1

（我遇到了同样的问题，我想将UIImageView添加到我的mainView并更新它们）我只是使用了想要在视图中显示的ViewControllers的NSMutable数组，然后添加或者根据需要从中减去，并且每次从该数组中添加或减去，然后从mainView中调用通过scrollView的metod并从scrollView中删除每个视图，然后将相应的viewController添加到scrollView。希望这会有所帮助。

更新ScrollView的内容

1 个答案: