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我使用UIScrollViews雷Wenderlich的(马特·加洛韦的)教程: http://www.raywenderlich.com/10518/how-to-use-uiscrollview-to-scroll-and-zoom-content如何更改Ray Wenderlich的UIScrollView教程的当前页面?
我在我的应用程序中使用的部分,“寻呼与UIScrollView的”。当你总是希望页面加载到0时,这很好用,但我希望当前页面是动态的。我将根据用户从前一个视图控制器(这是一个名为“listIndex”的NSInteger)中选择的缩略图传递此信息。
如何将当前页面更改为我的listIndex?我试图改变
self.pageControl.currentPage = 0;
到
self.pageControl.currentPage = self.listIndex;
在viewDidLoad中
,但这似乎并没有帮助 - 这可能是因为它得到复位的loadVisiblePages?
非常感谢您的帮助!下面的代码:
- (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);
}
}
完美!非常感谢。这正是我期待的行为。如果它始终必须设置为0,你是否认为currentPage的要点?我想我不明白他那个变量的原意。 – monalisa717
'self.pageControl.currentPage'确定'UIPageControl'中白点的索引。它在'viewDidLoad:'中初始化为0,但这并不重要,因为它根据scrollview的'contentOffset'在'loadVisiblePages'中设置为正确的值。这就是为什么在调用loadVisiblePages之前在'viewWillAppear:'中设置'contentOffset'的原因,因为'currentPage'将被设置为这个方法中的正确页面。 –