我正在使用Ray Wenderlich（Matt Galloway）的UIScrollViews教程：http://www.raywenderlich.com/10518/how-to-use-uiscrollview-to-scroll-and-zoom-content
我正在我的应用程序中使用"使用UIScrollView分页"部分。当您总是希望页面在0上加载，但我希望当前页面是动态的时，这非常有效。我将根据用户从上一个视图控制器中选择的缩略图来传递这些信息，该控制器是一个名为"listIndex"的NSInteger
如何将当前页面更改为我的listIndex？我试过更换
self.pageControl.currentPage = 0;
至
self.pageControl.currentPage = self.listIndex;
在viewDidLoad中，但这似乎没有帮助——可能是因为它在loadVisiblePages中被重置了？
非常感谢你的帮助！这是代码：
- (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)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)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)scrollViewDidScroll:(UIScrollView *)scrollView {
// Load the pages that are now on screen
[self loadVisiblePages];
}
- (void)viewDidLoad
{
[super viewDidLoad];
NSMutableString *myHTML = [[NSMutableString alloc] initWithString:@"<html><head><style type='text/css'> p {font-family:sans-serif; text-shadow: 3px 4px 5px #000; color:#FFF; position: absolute; bottom:0; font-size:10pt; font-weight:bold; margin-bottom:5px;}</style><body><p>"];
[myHTML appendString:self.caption];
[myHTML appendString:@"</p></body></html>"];
[captionWebView loadHTMLString:myHTML baseURL:nil];
self.pageImages = [NSMutableArray array];
for (int i=0; i < [imageList count]; i++) {
NSString *path = [(Image *)[imageList objectAtIndex:i] path];
[self.pageImages addObject:[UIImage imageNamed:path]];
}
NSInteger pageCount = self.pageImages.count;
// 2
self.pageControl.currentPage = 0;
//self.pageControl.currentPage = self.listIndex; //Tried this
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];
// add this in order UIScrollView work with Auto layout
if (IS_WIDESCREEN) {
self.scrollView.frame = CGRectMake(0, 0, 320, 468);
} else {
self.scrollView.frame = CGRectMake(0, 0, 320, 380);
}
// 4
CGSize pagesScrollViewSize = self.scrollView.frame.size;
self.scrollView.contentSize = CGSizeMake(pagesScrollViewSize.width * self.pageImages.count, pagesScrollViewSize.height);
// 5
[self loadVisiblePages];
}
- (void)viewWillDisappear:(BOOL)animated {
// add this in order UIScrollView work with Auto layout
if (IS_WIDESCREEN) {
self.scrollView.contentSize = CGSizeMake(320, 468);
} else {
self.scrollView.contentSize = CGSizeMake(320, 380);
}
}
尝试在viewWillAppear::中设置滚动视图的初始contentOffset
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
// Set up the content size of the scroll view
CGSize pagesScrollViewSize = self.scrollView.frame.size;
self.scrollView.contentSize = CGSizeMake(pagesScrollViewSize.width * self.pageImages.count, pagesScrollViewSize.height);
// Set initial content offset of scrollview
self.scrollView.contentOffset = CGPointMake(pagesScrollViewSize.width * self.listIndex, self.scrollView.contentOffset.y);
// Load the initial set of pages that are on screen
[self loadVisiblePages];
}