我在用于缩放和滚动的 UIScrollView
中有一个 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,当图像变得小于滚动视图时,它会粘在滚动视图的左上角。我想让它保持居中,就像照片应用程序一样。
关于在 UIScrollView
较小时保持内容居中的任何想法或示例?
我正在使用 iPhone 3.0。
以下代码几乎可以工作。如果我在达到最小缩放级别后捏它,图像会返回到左上角。
- (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)];
}
我有非常简单的解决方案!您只需在放大 ScrollViewDelegate 时更新子视图(图像视图)的中心。如果缩放图像小于滚动视图,则调整 subview.center 否则中心为 (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);
}
@EvelynCordner's answer 是在我的应用中效果最好的一个。代码也比其他选项少得多。
如果有人需要,这是 Swift 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)
}
好的,在过去的两天里,我一直在与这个作斗争,终于找到了一个非常可靠的(到目前为止......)解决方案,我认为我应该分享它并为其他人节省一些痛苦。 :) 如果您确实发现此解决方案有问题,请大喊!
我基本上已经完成了其他人所拥有的:搜索 StackOverflow、Apple 开发者论坛,查看了 three20、ScrollingMadness、ScrollTestSuite 等的代码。我尝试扩大 UIImageView 框架,使用 UIScrollView 的偏移量和/或插图来自 ViewController 等,但没有什么效果很好(其他人也发现了)。
睡在上面之后,我尝试了几个不同的角度:
子类化 UIImageView 以便它动态地改变它自己的大小 - 这一点都不好用。对 UIScrollView 进行子类化,使其动态更改自己的 contentOffset - 这对我来说似乎是赢家。
使用这个子类化 UIScrollView 方法,我将覆盖 contentOffset mutator,因此当图像缩放小于视口时它不会设置 {0,0} - 而是设置偏移量,以便图像将保持在视口中居中。到目前为止,它似乎总是有效。我已经用宽、高、小和大的图像检查了它,并且没有“工作但在最小缩放时捏会破坏它”的问题。
我已将使用此解决方案的示例项目上传到 github,您可以在此处找到它:http://github.com/nyoron/NYOBetterZoom
anOffset.y = -(scrollViewSize.height - zoomViewSize.height) / 2.0
更改为 anOffset.y = (-(scrollViewSize.height - zoomViewSize.height) / 2.0) + 10;
对于更适合使用自动布局的滚动视图的解决方案,请使用滚动视图的内容插入,而不是更新滚动视图的子视图的框架。
- (void)scrollViewDidZoom:(UIScrollView *)scrollView
{
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);
self.scrollView.contentInset = UIEdgeInsetsMake(offsetY, offsetX, 0.f, 0.f);
}
UIScrollview
内的 UIView
放在同一个中心 (view.center = scrollview.center;
),然后在 scrollViewDidZoom
中将 view.frame.origin
x
和 y
设置为 0
再次。
viewWillAppear
的主队列做了一个 dispatch_async
,我在主滚动视图上调用了 scrollViewDidZoom:
。这使视图以居中的图像显示。
viewDidLayoutSubviews
中调用此代码以确保在第一次显示视图时正确设置它。
这段代码应该可以在大多数版本的 iOS 上运行(并且已经过测试可以在 3.1 以上版本上运行)。
它基于 photocoller 的 Apple WWDC 代码。
将以下内容添加到 UIScrollView 的子类中,并将 tileContainerView 替换为包含您的图像或图块的视图:
- (void)layoutSubviews {
[super layoutSubviews];
// center the image as it becomes smaller than the size of the screen
CGSize boundsSize = self.bounds.size;
CGRect frameToCenter = tileContainerView.frame;
// center horizontally
if (frameToCenter.size.width < boundsSize.width)
frameToCenter.origin.x = (boundsSize.width - frameToCenter.size.width) / 2;
else
frameToCenter.origin.x = 0;
// center vertically
if (frameToCenter.size.height < boundsSize.height)
frameToCenter.origin.y = (boundsSize.height - frameToCenter.size.height) / 2;
else
frameToCenter.origin.y = 0;
tileContainerView.frame = frameToCenter;
}
UIScrollView
子类方法似乎更可取:它在第一次显示视图时调用 + 在进行缩放时连续调用(而 scrollViewDidZoom
仅在每次滚动后调用一次) )
目前我正在继承 UIScrollView
并覆盖 setContentOffset:
以根据 contentSize
调整偏移量。它适用于捏合和程序缩放。
@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,这段代码还产生了比@Erdemus 解决方案更平滑的缩放。您可以在 RMGallery 演示中看到它的实际效果。
我花了一天时间解决这个问题,最终实现了 scrollViewDidEndZooming:withView:atScale: 如下:
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale {
CGFloat screenWidth = [[UIScreen mainScreen] bounds].size.width;
CGFloat screenHeight = [[UIScreen mainScreen] bounds].size.height;
CGFloat viewWidth = view.frame.size.width;
CGFloat viewHeight = view.frame.size.height;
CGFloat x = 0;
CGFloat y = 0;
if(viewWidth < screenWidth) {
x = screenWidth / 2;
}
if(viewHeight < screenHeight) {
y = screenHeight / 2 ;
}
self.scrollView.contentInset = UIEdgeInsetsMake(y, x, y, x);
}
这可确保当图像小于屏幕时,它周围仍有足够的空间,因此您可以将其定位到您想要的确切位置。
(假设你的 UIScrollView 包含一个 UIImageView 来保存图像)
本质上,它的作用是检查您的图像视图的宽度/高度是否小于屏幕的宽度/高度,如果是,则创建一个屏幕宽度/高度一半的插图(如果您希望图像走出屏幕边界)。
请注意,由于这是一个 UIScrollViewDelegate 方法,请不要忘记将其添加到视图控制器的声明中,以避免出现构建问题。
Apple 已向 iphone 开发者计划的所有成员发布了 2010 年 WWDC 会议视频。讨论的主题之一是他们如何创建照片应用程序!!!他们逐步构建了一个非常相似的应用程序,并免费提供了所有代码。
它也不使用私有 api。由于保密协议,我不能把任何代码放在这里,但这里是示例代码下载的链接。您可能需要登录才能获得访问权限。
而且,这里是 iTunes WWDC 页面的链接:
如果其他任何内容都不需要 contentInset
,则可以使用它来居中滚动视图的内容。
class ContentCenteringScrollView: UIScrollView {
override var bounds: CGRect {
didSet { updateContentInset() }
}
override var contentSize: CGSize {
didSet { updateContentInset() }
}
private func updateContentInset() {
var top = CGFloat(0)
var left = CGFloat(0)
if contentSize.width < bounds.width {
left = (bounds.width - contentSize.width) / 2
}
if contentSize.height < bounds.height {
top = (bounds.height - contentSize.height) / 2
}
contentInset = UIEdgeInsets(top: top, left: left, bottom: top, right: left)
}
}
如果这种方法的优势在于您仍然可以使用 contentLayoutGuide
将内容放置在滚动视图中
scrollView.addSubview(imageView)
imageView.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
imageView.leadingAnchor.constraint(equalTo: scrollView.contentLayoutGuide.leadingAnchor),
imageView.trailingAnchor.constraint(equalTo: scrollView.contentLayoutGuide.trailingAnchor),
imageView.topAnchor.constraint(equalTo: scrollView.contentLayoutGuide.topAnchor),
imageView.bottomAnchor.constraint(equalTo: scrollView.contentLayoutGuide.bottomAnchor)
])
或者只是在 Xcode 的 Interface Builder 中拖放内容。
好的,这个解决方案对我有用。我有一个 UIScrollView
的子类,其中引用了它正在显示的 UIImageView
。每当 UIScrollView
缩放时,就会调整 contentSize 属性。在设置器中,我适当地缩放 UIImageView
并调整其中心位置。
-(void) setContentSize:(CGSize) size{
CGSize lSelfSize = self.frame.size;
CGPoint mid;
if(self.zoomScale >= self.minimumZoomScale){
CGSize lImageSize = cachedImageView.initialSize;
float newHeight = lImageSize.height * self.zoomScale;
if (newHeight < lSelfSize.height ) {
newHeight = lSelfSize.height;
}
size.height = newHeight;
float newWidth = lImageSize.width * self.zoomScale;
if (newWidth < lSelfSize.width ) {
newWidth = lSelfSize.width;
}
size.width = newWidth;
mid = CGPointMake(size.width/2, size.height/2);
}
else {
mid = CGPointMake(lSelfSize.width/2, lSelfSize.height/2);
}
cachedImageView.center = mid;
[super setContentSize:size];
[self printLocations];
NSLog(@"zoom %f setting size %f x %f",self.zoomScale,size.width,size.height);
}
每次我在 UIScrollView
上设置图像时,我都会调整它的大小。滚动视图中的 UIScrollView
也是我创建的自定义类。
-(void) resetSize{
if (!scrollView){//scroll view is view containing imageview
return;
}
CGSize lSize = scrollView.frame.size;
CGSize lSelfSize = self.image.size;
float lWidth = lSize.width/lSelfSize.width;
float lHeight = lSize.height/lSelfSize.height;
// choose minimum scale so image width fits screen
float factor = (lWidth<lHeight)?lWidth:lHeight;
initialSize.height = lSelfSize.height * factor;
initialSize.width = lSelfSize.width * factor;
[scrollView setContentSize:lSize];
[scrollView setContentOffset:CGPointZero];
scrollView.userInteractionEnabled = YES;
}
使用这两种方法,我可以拥有一个与照片应用程序一样的视图。
我这样做的方法是在层次结构中添加一个额外的视图:
UIScrollView -> UIView -> UIImageView
为您的 UIView
提供与 UIScrollView
相同的纵横比,并将您的 UIImageView
居中。
只是快速批准的答案,但没有使用委托进行子类化
func centerScrollViewContents(scrollView: UIScrollView) {
let contentSize = scrollView.contentSize
let scrollViewSize = scrollView.frame.size;
var contentOffset = scrollView.contentOffset;
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
}
scrollView.setContentOffset(contentOffset, animated: false)
}
// UIScrollViewDelegate
func scrollViewDidZoom(scrollView: UIScrollView) {
centerScrollViewContents(scrollView)
}
我知道上面的一些答案是正确的,但我只是想给出一些解释,评论会让你明白我们为什么这样做。
当我第一次加载滚动视图时,我编写了以下代码使其居中,请注意我们先设置contentOffset
,然后设置contentInset
scrollView.maximumZoomScale = 8
scrollView.minimumZoomScale = 1
// set vContent frame
vContent.frame = CGRect(x: 0,
y: 0 ,
width: vContentWidth,
height: vContentWidth)
// set scrollView.contentSize
scrollView.contentSize = vContent.frame.size
//on the X direction, if contentSize.width > scrollView.bounds.with, move scrollView from 0 to offsetX to make it center(using `scrollView.contentOffset`)
// if not, don't need to set offset, but we need to set contentInset to make it center.(using `scrollView.contentInset`)
// so does the Y direction.
let offsetX = max((scrollView.contentSize.width - scrollView.bounds.width) * 0.5, 0)
let offsetY = max((scrollView.contentSize.height - scrollView.bounds.height) * 0.5, 0)
scrollView.contentOffset = CGPoint(x: offsetX, y: offsetY)
let topX = max((scrollView.bounds.width - scrollView.contentSize.width) * 0.5, 0)
let topY = max((scrollView.bounds.height - scrollView.contentSize.height) * 0.5, 0)
scrollView.contentInset = UIEdgeInsets(top: topY, left: topX, bottom: 0, right: 0)
然后,当我捏 vContent 时,我编写以下代码使其居中。
func scrollViewDidZoom(_ scrollView: UIScrollView) {
//we just need to ensure that the content is in the center when the contentSize is less than scrollView.size.
let topX = max((scrollView.bounds.width - scrollView.contentSize.width) * 0.5, 0)
let topY = max((scrollView.bounds.height - scrollView.contentSize.height) * 0.5, 0)
scrollView.contentInset = UIEdgeInsets(top: topY, left: topX, bottom: 0, right: 0)
}
您可以观察 UIScrollView 的 contentSize
属性(使用键值观察或类似方法),并在 contentSize
更改为小于滚动视图大小时自动调整 contentInset
。
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale
(在 developer.apple.com/iphone/library/documentation/UIKit/… 中描述),但我更喜欢观察 contentSize
,否则您最终会丢弃新的缩放比例并从视图中找到它。 (除非您可以根据视图的相对大小得出一些很棒的数学。)
将 UISCrollView
的内容居中的一种优雅方式是这样。
向 UIScrollView
的 contentSize 添加一个观察者,因此每次内容更改时都会调用此方法...
[myScrollView addObserver:delegate
forKeyPath:@"contentSize"
options:(NSKeyValueObservingOptionNew)
context:NULL];
现在在你的观察者方法上:
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
// Correct Object Class.
UIScrollView *pointer = object;
// Calculate Center.
CGFloat topCorrect = ([pointer bounds].size.height - [pointer viewWithTag:100].bounds.size.height * [pointer zoomScale]) / 2.0 ;
topCorrect = ( topCorrect < 0.0 ? 0.0 : topCorrect );
topCorrect = topCorrect - ( pointer.frame.origin.y - imageGallery.frame.origin.y );
// Apply Correct Center.
pointer.center = CGPointMake(pointer.center.x,
pointer.center.y + topCorrect ); }
您应该更改 [pointer viewWithTag:100]。替换为您的内容视图 UIView。还要更改 imageGallery 指向您的窗口大小。
还要更改 imageGallery 指向您的窗口大小。
每次他的大小改变时,这将纠正内容的中心。
注意:此内容效果不佳的唯一方法是使用 UIScrollView
的标准缩放功能。
这是我对这个问题的解决方案,它适用于滚动视图中的任何类型的视图。
-(void)scrollViewDidZoom:(__unused UIScrollView *)scrollView
{
CGFloat top;
CGFloat left;
CGFloat bottom;
CGFloat right;
if (_scrollView.contentSize.width < scrollView.bounds.size.width) {
DDLogInfo(@"contentSize %@",NSStringFromCGSize(_scrollView.contentSize));
CGFloat width = (_scrollView.bounds.size.width-_scrollView.contentSize.width)/2.0;
left = width;
right = width;
}else {
left = kInset;
right = kInset;
}
if (_scrollView.contentSize.height < scrollView.bounds.size.height) {
CGFloat height = (_scrollView.bounds.size.height-_scrollView.contentSize.height)/2.0;
top = height;
bottom = height;
}else {
top = kInset;
right = kInset;
}
_scrollView.contentInset = UIEdgeInsetsMake(top, left, bottom, right);
if ([self.tiledScrollViewDelegate respondsToSelector:@selector(tiledScrollViewDidZoom:)])
{
[self.tiledScrollViewDelegate tiledScrollViewDidZoom:self];
}
}
这里有很多解决方案,但我会冒险将自己的解决方案放在这里。这有两个好处:它不会弄乱缩放体验,就像更新正在进行的图像视图框架一样,并且它尊重原始滚动视图插图(例如,在 xib 或情节提要中定义,以优雅地处理半透明工具栏等) .
首先,定义一个小助手:
CGSize CGSizeWithAspectFit(CGSize containerSize, CGSize contentSize) {
CGFloat containerAspect = containerSize.width / containerSize.height,
contentAspect = contentSize.width / contentSize.height;
CGFloat scale = containerAspect > contentAspect
? containerSize.height / contentSize.height
: containerSize.width / contentSize.width;
return CGSizeMake(contentSize.width * scale, contentSize.height * scale);
}
要保留原始插图,定义字段:
UIEdgeInsets originalScrollViewInsets;
在 viewDidLoad 的某个地方填充它:
originalScrollViewInsets = self.scrollView.contentInset;
将 UIImageView 放入 UIScrollView (假设 UIImage 本身在 loadedImage 变量中):
CGSize containerSize = self.scrollView.bounds.size;
containerSize.height -= originalScrollViewInsets.top + originalScrollViewInsets.bottom;
containerSize.width -= originalScrollViewInsets.left + originalScrollViewInsets.right;
CGSize contentSize = CGSizeWithAspectFit(containerSize, loadedImage.size);
UIImageView *imageView = [[UIImageView alloc] initWithFrame:(CGRect) { CGPointZero, contentSize }];
imageView.autoresizingMask = UIViewAutoresizingNone;
imageView.contentMode = UIViewContentModeScaleAspectFit;
imageView.image = loadedImage;
[self.scrollView addSubview:imageView];
self.scrollView.contentSize = contentSize;
[self centerImageViewInScrollView];
scrollViewDidZoom: 来自 UIScrollViewDelegate 的滚动视图:
- (void)scrollViewDidZoom:(UIScrollView *)scrollView {
if (scrollView == self.scrollView) {
[self centerImageViewInScrollView];
}
}
最后,以自身为中心:
- (void)centerImageViewInScrollView {
CGFloat excessiveWidth = MAX(0.0, self.scrollView.bounds.size.width - self.scrollView.contentSize.width),
excessiveHeight = MAX(0.0, self.scrollView.bounds.size.height - self.scrollView.contentSize.height),
insetX = excessiveWidth / 2.0,
insetY = excessiveHeight / 2.0;
self.scrollView.contentInset = UIEdgeInsetsMake(
MAX(insetY, originalScrollViewInsets.top),
MAX(insetX, originalScrollViewInsets.left),
MAX(insetY, originalScrollViewInsets.bottom),
MAX(insetX, originalScrollViewInsets.right)
);
}
我还没有测试方向变化(即调整 UIScrollView 本身大小的正确反应),但修复它应该相对容易。
您会发现 Erdemus 发布的解决方案确实有效,但是…… 在某些情况下,scrollViewDidZoom 方法没有被调用并且您的图像卡在左上角。一个简单的解决方案是在最初显示图像时显式调用该方法,如下所示:
[self scrollViewDidZoom: scrollView];
在许多情况下,您可能会调用此方法两次,但与本主题中的其他一些答案相比,这是一种更简洁的解决方案。
Apple 的 Photo Scroller 示例完全符合您的要求。把它放在你的 UIScrollView 子类中并将 _zoomView 更改为你的 UIImageView。
-(void)layoutSubviews{
[super layoutSubviews];
// center the zoom view as it becomes smaller than the size of the screen
CGSize boundsSize = self.bounds.size;
CGRect frameToCenter = self.imageView.frame;
// center horizontally
if (frameToCenter.size.width < boundsSize.width){
frameToCenter.origin.x = (boundsSize.width - frameToCenter.size.width) / 2;
}else{
frameToCenter.origin.x = 0;
}
// center vertically
if (frameToCenter.size.height < boundsSize.height){
frameToCenter.origin.y = (boundsSize.height - frameToCenter.size.height) / 2;
}else{
frameToCenter.origin.y = 0;
}
self.imageView.frame = frameToCenter;
}
Apple's Photo Scroller Sample Code
为了使动画流畅,设置
self.scrollview.bouncesZoom = NO;
并使用此功能(使用 this answer 处的方法找到中心)
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(CGFloat)scale {
[UIView animateWithDuration:0.2 animations:^{
float offsetX = MAX((scrollView.bounds.size.width-scrollView.contentSize.width)/2, 0);
float offsetY = MAX((scrollView.bounds.size.height-scrollView.contentSize.height)/2, 0);
self.imageCoverView.center = CGPointMake(scrollView.contentSize.width*0.5+offsetX, scrollView.contentSize.height*0.5+offsetY);
}];
}
这会产生弹跳效果,但事先不涉及任何突然的运动。
如果您的内部 imageView 具有初始特定宽度(例如 300),并且您只想将其宽度集中在小于其初始宽度的缩放上,这也可能对您有所帮助。
func scrollViewDidZoom(scrollView: UIScrollView){
if imageView.frame.size.width < 300{
imageView.center.x = self.view.frame.width/2
}
}
这是我目前的工作方式。它更好,但仍然不完美。尝试设置:
myScrollView.bouncesZoom = YES;
解决在 minZoomScale
时视图不居中的问题。
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
CGSize screenSize = [[self view] bounds].size;//[[UIScreen mainScreen] bounds].size;//
CGSize photoSize = [yourImage size];
CGFloat topInset = (screenSize.height - photoSize.height * [myScrollView zoomScale]) / 2.0;
CGFloat sideInset = (screenSize.width - photoSize.width * [myScrollView zoomScale]) / 2.0;
if (topInset < 0.0)
{ topInset = 0.0; }
if (sideInset < 0.0)
{ sideInset = 0.0; }
[myScrollView setContentInset:UIEdgeInsetsMake(topInset, sideInset, -topInset, -sideInset)];
ApplicationDelegate *appDelegate = (ApplicationDelegate *)[[UIApplication sharedApplication] delegate];
CGFloat scrollViewHeight; //Used later to calculate the height of the scrollView
if (appDelegate.navigationController.navigationBar.hidden == YES) //If the NavBar is Hidden, set scrollViewHeight to 480
{ scrollViewHeight = 480; }
if (appDelegate.navigationController.navigationBar.hidden == NO) //If the NavBar not Hidden, set scrollViewHeight to 360
{ scrollViewHeight = 368; }
imageView.frame = CGRectMake(0, 0, CGImageGetWidth(yourImage)* [myScrollView zoomScale], CGImageGetHeight(yourImage)* [myScrollView zoomScale]);
[imageView setContentMode:UIViewContentModeCenter];
}
另外,我执行以下操作以防止图像在缩小后粘在侧面。
- (void) scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale {
myScrollView.frame = CGRectMake(0, 0, 320, 420);
//put the correct parameters for your scroll view width and height above
}
好的,我想我已经找到了一个很好的解决这个问题的方法。诀窍是不断地重新调整 imageView's
框架。我发现这比不断调整 contentInsets
或 contentOffSets
要好得多。我不得不添加一些额外的代码来容纳纵向和横向图像。
这是代码:
- (void) scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale {
CGSize screenSize = [[self view] bounds].size;
if (myScrollView.zoomScale <= initialZoom +0.01) //This resolves a problem with the code not working correctly when zooming all the way out.
{
imageView.frame = [[self view] bounds];
[myScrollView setZoomScale:myScrollView.zoomScale +0.01];
}
if (myScrollView.zoomScale > initialZoom)
{
if (CGImageGetWidth(temporaryImage.CGImage) > CGImageGetHeight(temporaryImage.CGImage)) //If the image is wider than tall, do the following...
{
if (screenSize.height >= CGImageGetHeight(temporaryImage.CGImage) * [myScrollView zoomScale]) //If the height of the screen is greater than the zoomed height of the image do the following...
{
imageView.frame = CGRectMake(0, 0, 320*(myScrollView.zoomScale), 368);
}
if (screenSize.height < CGImageGetHeight(temporaryImage.CGImage) * [myScrollView zoomScale]) //If the height of the screen is less than the zoomed height of the image do the following...
{
imageView.frame = CGRectMake(0, 0, 320*(myScrollView.zoomScale), CGImageGetHeight(temporaryImage.CGImage) * [myScrollView zoomScale]);
}
}
if (CGImageGetWidth(temporaryImage.CGImage) < CGImageGetHeight(temporaryImage.CGImage)) //If the image is taller than wide, do the following...
{
CGFloat portraitHeight;
if (CGImageGetHeight(temporaryImage.CGImage) * [myScrollView zoomScale] < 368)
{ portraitHeight = 368;}
else {portraitHeight = CGImageGetHeight(temporaryImage.CGImage) * [myScrollView zoomScale];}
if (screenSize.width >= CGImageGetWidth(temporaryImage.CGImage) * [myScrollView zoomScale]) //If the width of the screen is greater than the zoomed width of the image do the following...
{
imageView.frame = CGRectMake(0, 0, 320, portraitHeight);
}
if (screenSize.width < CGImageGetWidth (temporaryImage.CGImage) * [myScrollView zoomScale]) //If the width of the screen is less than the zoomed width of the image do the following...
{
imageView.frame = CGRectMake(0, 0, CGImageGetWidth(temporaryImage.CGImage) * [myScrollView zoomScale], portraitHeight);
}
}
[myScrollView setZoomScale:myScrollView.zoomScale -0.01];
}
只需禁用分页,它就可以正常工作:
scrollview.pagingEnabled = NO;
我有同样的问题。这是我解决的方法
此代码应作为 scrollView:DidScroll:
的结果调用
CGFloat imageHeight = self.imageView.frame.size.width * self.imageView.image.size.height / self.imageView.image.size.width;
BOOL imageSmallerThanContent = (imageHeight < self.scrollview.frame.size.height) ? YES : NO;
CGFloat topOffset = (self.imageView.frame.size.height - imageHeight) / 2;
// If image is not large enough setup content offset in a way that image is centered and not vertically scrollable
if (imageSmallerThanContent) {
topOffset = topOffset - ((self.scrollview.frame.size.height - imageHeight)/2);
}
self.scrollview.contentInset = UIEdgeInsetsMake(topOffset * -1, 0, topOffset * -1, 0);
虽然这个问题有点老了,但问题仍然存在。我在 Xcode 7 中解决了这个问题,方法是将最上面的项目(在本例中为 topLabel
)到超级视图(scrollView
)的垂直空间约束设置为 IBOutlet
,然后重新计算其每次内容根据 scrollView 的子视图(topLabel
和 bottomLabel
)的高度而变化时保持不变。
class MyViewController: UIViewController {
@IBOutlet weak var scrollView: UIScrollView!
@IBOutlet weak var topLabel: UILabel!
@IBOutlet weak var bottomLabel: UILabel!
@IBOutlet weak var toTopConstraint: NSLayoutConstraint!
override func viewDidLayoutSubviews() {
let heightOfScrollViewContents = (topLabel.frame.origin.y + topLabel.frame.size.height - bottomLabel.frame.origin.y)
// In my case abs() delivers the perfect result, but you could also check if the heightOfScrollViewContents is greater than 0.
toTopConstraint.constant = abs((scrollView.frame.height - heightOfScrollViewContents) / 2)
}
func refreshContents() {
// Set the label's text …
self.view.layoutIfNeeded()
}
}
一个 Swift 版本,它只是子类 UIScrollView
并自己夸大子视图。它工作得非常顺利。
import UIKit
class CenteringScrollView: UIScrollView {
override func layoutSubviews() {
super.layoutSubviews()
if zoomScale < 1.0 {
if let subview = self.subviews.first {
subview.center.x = self.center.x
}
}
}
}
viewForZooming(in:)
CGFloat offsetX = MAX((scrollView.bounds.size.width - scrollView.contentSize.width) * 0.5, 0.0);
CGFloat offsetX = MAX((scrollView.bounds.size.width - scrollView.contentInset.left - scrollView.contentInset.right - scrollView.contentSize.width) * 0.5, 0.0); CGFloat offsetY = MAX((scrollView.bounds.size.height - scrollView.contentInset.top - scrollView.contentInset.bottom - scrollView.contentSize.height) * 0.5, 0.0);
zoomToRect:
时似乎遇到了问题。如果您碰巧需要该功能,则使用contentInset
方法效果更好。有关详细信息,请参阅 petersteinberger.com/blog/2013/how-to-center-uiscrollview。