较小时将UIScrollView的内容居中
较小时将UIScrollView的内容居中
提问于 2009-08-23 00:55:21
我在UIScrollView中有一个用于缩放和滚动的UIImageView。如果滚动视图的图像/内容大于滚动视图，则一切正常。但是，当图像变得比滚动视图小时，它会停留在滚动视图的左上角。我想让它居中，就像照片应用程序一样。
有什么想法或例子可以让UIScrollView的内容在较小的时候居中显示吗？
我正在使用iPhone 3.0。
下面的代码几乎可以正常工作。如果我在达到最小缩放级别后收缩图像，图像将返回到左上角。
- (void)loadView {
[super loadView];
// set up main scroll view
imageScrollView = [[UIScrollView alloc] initWithFrame:[[self view] bounds]];
[imageScrollView setBackgroundColor:[UIColor blackColor]];
[imageScrollView setDelegate:self];
[imageScrollView setBouncesZoom:YES];
[[self view] addSubview:imageScrollView];
UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"WeCanDoIt.png"]];
[imageView setTag:ZOOM_VIEW_TAG];
[imageScrollView setContentSize:[imageView frame].size];
[imageScrollView addSubview:imageView];
CGSize imageSize = imageView.image.size;
[imageView release];
CGSize maxSize = imageScrollView.frame.size;
CGFloat widthRatio = maxSize.width / imageSize.width;
CGFloat heightRatio = maxSize.height / imageSize.height;
CGFloat initialZoom = (widthRatio > heightRatio) ? heightRatio : widthRatio;
[imageScrollView setMinimumZoomScale:initialZoom];
[imageScrollView setZoomScale:1];
float topInset = (maxSize.height - imageSize.height) / 2.0;
float sideInset = (maxSize.width - imageSize.width) / 2.0;
if (topInset < 0.0) topInset = 0.0;
if (sideInset < 0.0) sideInset = 0.0;
[imageScrollView setContentInset:UIEdgeInsetsMake(topInset, sideInset, -topInset, -sideInset)];
}
- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
return [imageScrollView viewWithTag:ZOOM_VIEW_TAG];
}
/************************************** NOTE **************************************/
/* The following delegate method works around a known bug in zoomToRect:animated: */
/* In the next release after 3.0 this workaround will no longer be necessary */
/**********************************************************************************/
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale {
[scrollView setZoomScale:scale+0.01 animated:NO];
[scrollView setZoomScale:scale animated:NO];
// END Bug workaround
CGSize maxSize = imageScrollView.frame.size;
CGSize viewSize = view.frame.size;
float topInset = (maxSize.height - viewSize.height) / 2.0;
float sideInset = (maxSize.width - viewSize.width) / 2.0;
if (topInset < 0.0) topInset = 0.0;
if (sideInset < 0.0) sideInset = 0.0;
[imageScrollView setContentInset:UIEdgeInsetsMake(topInset, sideInset, -topInset, -sideInset)];
}回答 22
Stack Overflow用户
回答已采纳
发布于 2014-03-21 20:06:47
目前，我正在对UIScrollView进行子类化，并重写setContentOffset:以根据contentSize调整偏移量。它既适用于收缩，也适用于编程缩放。
@implementation HPCenteringScrollView
- (void)setContentOffset:(CGPoint)contentOffset
{
const CGSize contentSize = self.contentSize;
const CGSize scrollViewSize = self.bounds.size;
if (contentSize.width < scrollViewSize.width)
{
contentOffset.x = -(scrollViewSize.width - contentSize.width) / 2.0;
}
if (contentSize.height < scrollViewSize.height)
{
contentOffset.y = -(scrollViewSize.height - contentSize.height) / 2.0;
}
[super setContentOffset:contentOffset];
}
@end除了短小精悍之外，这段代码还能产生比@Erdemus解决方案更平滑的缩放效果。您可以在RMGallery演示中看到它的实际效果。
Stack Overflow用户
发布于 2010-05-22 15:25:10
我有一个非常简单的解决方案！您所需要做的就是在放大ScrollViewDelegate时更新子视图(图像视图)的中心。如果缩放图像小于scrollview，则调整中心，否则subview.center为(0,0)。
- (void)scrollViewDidZoom:(UIScrollView *)scrollView
{
UIView *subView = [scrollView.subviews objectAtIndex:0];
CGFloat offsetX = MAX((scrollView.bounds.size.width - scrollView.contentSize.width) * 0.5, 0.0);
CGFloat offsetY = MAX((scrollView.bounds.size.height - scrollView.contentSize.height) * 0.5, 0.0);
subView.center = CGPointMake(scrollView.contentSize.width * 0.5 + offsetX,
scrollView.contentSize.height * 0.5 + offsetY);
}Stack Overflow用户
发布于 2016-03-23 13:57:01
在我的应用中，@EvelynCordner's answer是运行得最好的一个。与其他选项相比，代码也要少得多。
如果有人需要的话，这是Swift的版本：
func scrollViewDidZoom(_ scrollView: UIScrollView) {
let offsetX = max((scrollView.bounds.width - scrollView.contentSize.width) * 0.5, 0)
let offsetY = max((scrollView.bounds.height - scrollView.contentSize.height) * 0.5, 0)
scrollView.contentInset = UIEdgeInsetsMake(offsetY, offsetX, 0, 0)
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/1316451
复制相关文章
相似问题