较小时，UIScrollView的中心内容

我有一个UIImageView内部UIScrollView，可用于缩放和滚动。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，它将停留在滚动视图的左上角。我想使其保持居中状态，例如“照片”应用程序。

关于UIScrollView缩小内容时保持居中的内容有什么想法或例子吗？

我正在使用iPhone 3.0。

以下代码几乎可以正常工作。如果在达到最小缩放级别后捏住图像，图像将返回左上角。

- (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)];
}

我有一个非常简单的解决方案！您需要做的就是在放大ScrollViewDelegate的同时更新子视图（imageview）的中心。如果缩放的图像小于滚动视图，则调整subview.center，否则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);
}

@EvelynCordner的答案是在我的应用程序中效果最好的答案。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，过去两天来我一直在与这个问题进行斗争，最终找到了一个相当可靠的解决方案（到目前为止...），我想我应该分享它，并减轻其他人的痛苦。:)如果您发现此解决方案有问题，请大喊！

我基本上已经遍历了其他所有人所拥有的东西：搜索StackOverflow，Apple Developer Forums，查看three20，ScrollingMadness，ScrollTestSuite等的代码。我尝试放大UIImageView框架，使用UIScrollView的偏移量和/或插图从ViewController等中获取结果，但没有任何效果很好（其他所有人也发现了）。

睡在上面之后，我尝试了几种其他角度：

1. 子类化UIImageView，以便它动态地更改其自身的大小-这根本无法正常工作。
2. 继承UIScrollView的子类，以便它动态更改其自己的contentOffset-这似乎是我的赢家。

通过这种子类化的UIScrollView方法，我重写了contentOffset mutator，因此当图像的缩放比例小于视口时，它不会设置{0,0}-而是设置偏移量，以使图像将在视口中居中。到目前为止，它似乎总是可行。我已经检查了宽，高，小和大的图像，但没有“有效但捏到最小变焦会破坏它”的问题。

我已经将使用该解决方案的示例项目上传到github，您可以在这里找到它：http : //github.com/nyoron/NYOBetterZoom

此代码应可在大多数版本的iOS上运行（并且已经过测试，可在3.1或更高版本上运行）。

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;
}

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图，而不要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);
}

目前，我正在子类化UIScrollView和覆盖setContentOffset:以基于调整偏移量contentSize。它适用于捏和程序缩放。

@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

除了简短有趣之外，此代码还可以产生比@Erdemus解决方案更平滑的缩放。您可以在RMGallery演示中看到它的运行情况。

我花了一天的时间来解决这个问题，并最终实现了scrollViewDidEndZooming：withView：atScale：，如下所示：

- (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);
}

这样可以确保当图像小于屏幕时，其周围仍然有足够的空间，以便可以将其放置在所需的确切位置。

（假设您的UIScrollView包含一个UIImageView来保存图像）

本质上，这是检查图像视图的宽度/高度是否小于屏幕的宽度/高度，如果是，则创建屏幕宽度/高度的一半的插图（如果您希望图像变大，则可以将其放大超出屏幕范围）。

请注意，由于这是一个UIScrollViewDelegate方法，所以请不要忘记将其添加到视图控制器的声明中，以免出现构建问题。

苹果已经向iphone开发人员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。由于未达成披露协议，我无法在此处放置任何代码，但这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。

http://connect.apple.com/cgi-bin/WebObjects/MemberSite.woa/wa/getSoftware?code=y&source=x&bundleID=20645

而且，这是iTunes WWDC页面的链接：

http://insideapple.apple.com/redir/cbx-cgi.do?v=2&la=en&lc=&a=kGSol9sgPHP%2BtlWtLp%2BEP%2FnxnZarjWJglPBZRHd3oDbACudP51JNGS8KlsFgxZto9X%2BTsnqSbeUSWX0doe%2Fzv%2FN5XV55%2FomsyfRgFBysOnIVggO%2Fn2p%2BiweDK%2F%2FmsIXj

好的，这个解决方案对我有用。我有一个UIScrollView参考的子类，UIImageView它正在显示。每当UIScrollView缩放时，都会调整contentSize属性。我会在二传手中UIImageView适当缩放比例，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);
}

每次我将图像设置在UIScrollView我调整大小。将UIScrollView在滚动视图也是我创建了一个自定义类。

-(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类似的视图。

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

给与您UIView相同的宽高比UIScrollView，然后将其居中UIImageView。

我知道上面的一些答案是正确的，但是我只想给出一些解释，这些注释将使您理解我们为什么这样做。

首次加载scrollView时，我编写了以下代码以使其居中，请注意，我们contentOffset首先进行了设置，然后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，当我捏住vContent时，我编写以下代码以使其居中。

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)
}

如果contentInset不需要其他任何内容，则可以将其用于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contentLayoutGuide可以将内容放置在scrollview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)
])

或者只是将内容拖放到Xcode的Interface Builder中。

您可以观察contentSizeUIScrollView 的属性（使用键值观察或类似方法），并contentInset在contentSize更改小于滚动视图的大小时自动调整。

一种使内容居中的优雅方法UISCrollView是。

在您的contentSize中添加一个观察者UIScrollView，以便每次内容更改时都会调用此方法...

[myScrollView addObserver:delegate 
               forKeyPath:@"contentSize"
                  options:(NSKeyValueObservingOptionNew) 
                  context:NULL];

现在在您的观察者方法上：

- (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]。用内容视图替换UIView。

  • 也更改imageGallery指向您的窗口大小。

每当他的尺寸改变时，这将校正内容的中心。

注意：此内容无法正常使用的唯一方法是使用的标准缩放功能UIScrollView。

这是我对这个问题的解决方案，它对于滚动视图内的任何视图都可以正常工作。

-(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，但是我冒着自己的风险。这样做有两个方面的好处：不会像正在更新图像视图框架那样使缩放体验混乱，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，请定义字段：

UIEdgeInsets originalScrollViewInsets;

然后在viewDidLoad中的某处填充它：

originalScrollViewInsets = self.scrollView.contentInset;

要将UIImageView放入UIScrollView中（假设UIImage本身位于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：从UIScrollViewDelegate获得该滚动视图：

- (void)scrollViewDidZoom:(UIScrollView *)scrollView {
    if (scrollView == self.scrollView) {
        [self centerImageViewInScrollView];
    }
}

最后，以自己为中心：

- (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)
    );
}

我还没有测试方向的改变（即对调整UIScrollView本身的大小做出适当的反应），但是对此的修复应该相对容易。

您会发现Erdemus发布的解决方案确实有效，但是…在某些情况下，不会调用scrollViewDidZoom方法，并且图像会停留在左上角。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，您可能会两次调用此方法，但这是比本主题中的其他一些答案更干净的解决方案。

Apple的Photo Scroller Example完全满足您的需求。将其放在您的UIScrollView子类中，并将_zoomView更改为您的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; 
}

苹果的照片滚动器示例代码

为了使动画流畅，设置

self.scrollview.bouncesZoom = NO;

并使用此功能（使用此答案中的方法找到中心）

- (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，但不会涉及任何突然的运动。

快速批准的答案，但不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)
}

如果你内心的ImageView具有初始特定宽度（例如300），你只是要居中其宽度只有在放大比其初始宽度较小这可以帮助你也。

 func scrollViewDidZoom(scrollView: UIScrollView){
    if imageView.frame.size.width < 300{
        imageView.center.x = self.view.frame.width/2
    }
  }

这是我目前进行这项工作的方式。更好，但仍然不完美。尝试设置：

 myScrollView.bouncesZoom = YES; 

修复问题，使视图在时不居中minZoomScale。

- (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缩小后图像残留在侧面。

- (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，我想我已经找到了解决这个问题的不错的方法。诀窍是不断调整imageView's框架。我发现此方法比不断调整contentInsetsor 更好contentOffSets。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，即可正常使用：

scrollview.pagingEnabled = NO;

我有同样的问题。这是我解决的方法

此代码应作为的结果调用 scrollView:DidScroll:

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);

尽管问题有点老，但问题仍然存在。我在Xcode 7中解决了此问题，方法是使最上面的项（在本例中为topLabel）到superViews 的垂直空间约束（到scrollView）top an IBOutlet，然后每当内容根据scrollView的子视图的高度更改时重新计算其常数（topLabel和bottomLabel）。

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()
    }
}