ios - 在 UITabController 中使用 UIScrollview 来显示不显示所有页面的 UIImageView

Question

我正在关注 How To Use UIScrollView to Scroll and Zoom Content 的“使用 UIScrollView 分页”部分将 4 张图像加载到阵列中。我应该提到我正在 UITabController 中加载它，它是 Storyboard中的第一个 View Controller 。

出于某种原因，加载 View 时会出现两个问题:

其一，页面控件不响应来自 UIScrollView 的更新(点根本不移动，但计算正确的页数)。

第二，只有前两个页面加载，这让我觉得 loadVisiblePages 方法不起作用。

从 View Controller 的 First Responder 连接的是一个页面控件到 pageControl，一个 Scroll View 到 scrollView 和 view 到 View(默认)，最后是关系 segue。

更新:我刚刚发现关于这个问题的一些有趣的事情。如果我转到第 3 页(也就是数组中的第 3 个图像)，我看不到图像。但是，如果我切换选项卡，页面控件和图像都会正确显示。

标题:

#import <UIKit/UIKit.h>

@interface TutorialViewController : UIViewController <UIScrollViewDelegate>

@property (nonatomic, strong) IBOutlet UIScrollView *scrollView;
@property (nonatomic, strong) IBOutlet UIPageControl *pageControl;

@end

实现:

#import "TutorialViewController.h"

@interface TutorialViewController ()
@property (nonatomic, strong) NSArray *pageImages;
@property (nonatomic, strong) NSMutableArray *pageViews;

- (void)loadVisiblePages;
- (void)loadPage:(NSInteger)page;
- (void)purgePage:(NSInteger)page;
@end

@implementation TutorialViewController

@synthesize scrollView = _scrollView;
@synthesize pageControl = _pageControl;

@synthesize pageImages = _pageImages;
@synthesize pageViews = _pageViews;

- (void)loadPage:(NSInteger)page {
    if (page < 0 || page >= self.pageImages.count) {
        // If it's outside the range of what you have to display, then do nothing
        return;
    }

    // 1
    UIView *pageView = [self.pageViews objectAtIndex:page];
    if ((NSNull*)pageView == [NSNull null]) {
        // 2
        CGRect frame = self.scrollView.bounds;
        frame.origin.x = frame.size.width * page;
        frame.origin.y = 0.0f;

        // 3
        UIImageView *newPageView = [[UIImageView alloc] initWithImage:[self.pageImages objectAtIndex:page]];
        newPageView.contentMode = UIViewContentModeScaleAspectFit;
        newPageView.frame = frame;
        [self.scrollView addSubview:newPageView];
        // 4
        [self.pageViews replaceObjectAtIndex:page withObject:newPageView];
    }
}

- (void)purgePage:(NSInteger)page {
    if (page < 0 || page >= self.pageImages.count) {
        // If it's outside the range of what you have to display, then do nothing
        return;
    }

    // Remove a page from the scroll view and reset the container array
    UIView *pageView = [self.pageViews objectAtIndex:page];
    if ((NSNull*)pageView != [NSNull null]) {
        [pageView removeFromSuperview];
        [self.pageViews replaceObjectAtIndex:page withObject:[NSNull null]];
    }
}

- (void)loadVisiblePages {
    // First, determine which page is currently visible
    CGFloat pageWidth = self.scrollView.frame.size.width;
    NSInteger page = (NSInteger)floor((self.scrollView.contentOffset.x * 2.0f + pageWidth) / (pageWidth * 2.0f));

    // Update the page control
    self.pageControl.currentPage = page;

    // Work out which pages you want to load
    NSInteger firstPage = page - 1;
    NSInteger lastPage = page + 1;

    // Purge anything before the first page
    for (NSInteger i=0; i<firstPage; i++) {
        [self purgePage:i];
    }

    // Load pages in our range
    for (NSInteger i=firstPage; i<=lastPage; i++) {
        [self loadPage:i];
    }

    // Purge anything after the last page
    for (NSInteger i=lastPage+1; i<self.pageImages.count; i++) {
        [self purgePage:i];
    }
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    // Load the pages that are now on screen
    [self loadVisiblePages];
}

- (void)viewDidLoad {
    [super viewDidLoad];

    // 1
    self.pageImages = [NSArray arrayWithObjects:
                       [UIImage imageNamed:@"640x960 tutorial_1.png"],
                       [UIImage imageNamed:@"640x960 tutorial_2.png"],
                       [UIImage imageNamed:@"640x960 tutorial_3.png"],
                       [UIImage imageNamed:@"640x960 tutorial_4.png"],
                       nil];

    NSInteger pageCount = self.pageImages.count;

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

    // 3
    self.pageViews = [[NSMutableArray alloc] init];
    for (NSInteger i = 0; i < pageCount; ++i) {
        [self.pageViews addObject:[NSNull null]];
    }
}

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];

    // 4
    CGSize pagesScrollViewSize = self.scrollView.frame.size;
    self.scrollView.contentSize = CGSizeMake(pagesScrollViewSize.width * self.pageImages.count, pagesScrollViewSize.height);

    // 5
    [self loadVisiblePages];
}

@end

Answer 1

我终于明白了。

用户错误。我将 View 而不是我的 ViewController 链接为 Storyboard 中的委托(delegate)。

感谢观看，我希望这对其他人有帮助，这样他们 2 天就不用拔头发了!