我正在学习如何使用UIScrollView滚动和缩放数组中加载了4张图像的内容的"使用UIScrillView分页"部分。我应该提到的是，我正在UITabController中加载它，它是故事板中的第一个视图控制器。
由于某些原因，加载视图时会出现两个问题：
首先，页面控件不响应UIScrollView的更新(点根本不会移动，而是用正确的页数计算)。
第二，只有前两个页面加载，这让我认为loadVisiblePages方法不起作用。
从视图控制器的第一个响应程序连接起来的是一个页面控件到页面控件，以及一个滚动视图到滚动视图和视图到视图(默认)，最后是关系分段。
更新：我刚刚发现这个问题很有趣。如果我转到第3页(数组中的3个图像)，我看不到图像。但如果我切换选项卡，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
实施：
#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
我终于想通了。
用户错误。我将视图而不是我的ViewController链接为故事板中的代理。
感谢收看，我希望这能帮助其他人，这样他们两天内就不用拔头发了！