Question

我试图在水平ScrollView上显示我的广告图像，就像App Store顶部的滚动视图一样。图像的大小为320 * 180。

我的问题是：如果我将滚动视图的框架设置为320 * 568，它可以正常工作，但如果我将其设置为320 * 180（它应该是），则ScrollView不再滚动。

这是我的代码：

#import "AdsScrollViewController.h"

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

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

@implementation AdsScrollViewController
@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
NSLog(@"load visible pages");
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)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
self.pageImages = [NSArray arrayWithObjects:
                   [UIImage imageNamed:@"ad1.jpg"],
                   [UIImage imageNamed:@"ad2.jpg"],
                   [UIImage imageNamed:@"ad3.jpg"],
                   [UIImage imageNamed:@"ad1.jpg"],
                   [UIImage imageNamed:@"ad2.jpg"],
                   nil];

NSInteger pageCount = 5;//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]];
}
self.scrollView.delegate = self;
}

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

// 4

[_scrollView setScrollEnabled:YES];
CGSize pagesScrollViewSize = self.scrollView.frame.size;
self.scrollView.contentSize = CGSizeMake(pagesScrollViewSize.width * 5, 568);// pagesScrollViewSize.height);
NSLog(@"view will appear");
NSLog(@"%f, %f",self.scrollView.frame.size.height,self.scrollView.frame.size.width);
// 5
[self loadVisiblePages];
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
   NSLog(@"scrollViewDidScroll");
// Load the pages which are now on screen
[self loadVisiblePages];

}

@end

Answer 1

假设，就像你说的那样，你要显示的所有图像都是320x180或相同的宽高比，你可以在loadPage中更改以下代码：

    CGRect frame = self.scrollView.bounds;
    frame.origin.x = frame.size.width * page;
    frame.origin.y = 0.0f;

到以下块：

    CGRect frame = CGRectMake(320*page, 0 , 320, 180);
    self.scrollView.contentSize = CGSizeMake(320*(page+1),180);

我相信这应该解决这个特殊问题。但是，如果要在图片中使用动态大小，则可以使用float变量来跟踪scrollView的宽度，并在向其添加新子视图时相应地增加。

无法使用ScrollView for IOS进行水平滚动

1 个答案: