UIScrollView的中心内容较小时-Java 学习之路

135

我在 UIScrollView 里面有一个 UIImageView ，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，它会粘在滚动视图的左上角 . 我想让它保持中心，就像照片应用程序一样 .

有关保持 UIScrollView 内容较小的任何想法或示例？

我正在使用iPhone 3.0 .

以下代码几乎可以使用 . 如果在达到最小缩放级别后将其捏住，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)];
}

24 回答

我有一个非常简单的解决方案！您只需在放大ScrollViewDelegate时更新子视图（imageview）的中心即可 . 如果缩放图像小于scrollview，则调整subview.center else 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);
}

回复于 2024-04-27T20:42:01+08:00

@EvelynCordner's answer是我的应用程序中效果最好的那个 . 比其他选项少得多的代码 .

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)
}

回复于 2024-04-27T20:42:01+08:00

1
好吧，过去两天我一直在争吵这个问题，终于找到了一个非常可靠的（迄今为止......）解决方案，我认为我应该分享它并为其他人带来一些痛苦 . :)如果您确实发现此解决方案的问题，请大声喊！

我基本上已经了解了其他人的所有内容：搜索StackOverflow，Apple开发者论坛，查看了three20，ScrollingMadness，ScrollTestSuite等的代码 . 我尝试放大UIImageView框架，使用UIScrollView的偏移和/或插入来自ViewController等，但没有什么工作得很好（正如其他人也发现的那样） .

在睡觉之后，我尝试了几个不同的角度：
- 对UIImageView进行子类化以使其改变它's own size dynamically - this didn' t工作得很好 .
- 对UIScrollView进行子类化，使其动态地改变它自己的contentOffset - 这对我来说似乎是一个胜利者 .
使用这个子类化UIScrollView方法，我覆盖了contentOffset mutator，因此当图像缩放比视口小时，它不会设置{0,0} - 而是设置偏移量，使图像在视口中保持居中 . 到目前为止，似乎总是有效 . 我用宽，高，小和大的图像检查它，并没有“工作，但捏最小缩放打破它”问题 .

我已经将一个示例项目上传到使用此解决方案的github，您可以在此处找到它：http://github.com/nyoron/NYOBetterZoom
回复于 2024-04-27T20:42:01+08:00

此代码应适用于大多数iOS版本（并且已经过测试，可以在3.1版本上运行） .

它基于photoscoller的Apple WWDC代码 .

将以下内容添加到UIScrollView的子类中，并将tileContainerView替换为包含图像或切片的视图：

- (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;
}

回复于 2024-04-27T20:42:01+08:00

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帧 .

- (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);
}

回复于 2024-04-27T20:42:01+08:00

目前我正在继承 UIScrollView 并重写 setContentOffset: 以根据 contentSize 调整偏移量 . 它适用于捏合和编程缩放 .

@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

除了简短和甜美之外，这段代码比@Erdemus解决方案产生更加平滑的缩放 . 您可以在RMGallery演示中看到它的运行情况 .

回复于 2024-04-27T20:42:01+08:00

1
我花了一天时间来解决这个问题，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，周围仍有足够的空间，因此您可以将其放置在所需的确切位置 .

（假设你的UIScrollView包含一个UIImageView来保存图像）

基本上，这样做是检查你的图像视图的宽度/高度是否小于屏幕的宽度/高度，如果是这样，创建一个屏幕宽度/高度的一半的插入（如果你想要图像，你可能会更大走出屏幕边界） .

请注意，由于这是一个UIScrollViewDelegate方法，因此要避免出现构建问题 .
回复于 2024-04-27T20:42:01+08:00
0

Apple已向iphone开发者计划的所有成员发布了2010 WWDC会话视频 . 讨论的主题之一是他们如何创建照片应用程序！他们逐步构建一个非常相似的应用程序，并使所有代码免费提供 .

它也不使用私有api . 由于非公开协议，我不能在此处放置任何代码，但这里是示例代码的链接下载 . 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

并且，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

回复于 2024-04-27T20:42:01+08:00

好的，这个解决方案对我有用 . 我有一个 UIScrollView 的子类，它引用了它正在显示的 UIImageView . 每当 UIScrollView 缩放时，都会调整contentSize属性 . 在设定器中，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);
}

Evertime我在 UIScrollView 上设置了图像我调整了它的大小 . scrollview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;
}

通过这两种方法，我可以拥有一个与照片应用程序一样的视图 .

回复于 2024-04-27T20:42:01+08:00

0

您可以观察UIScrollView的 contentSize 属性（使用键值观察或类似），并在 contentSize 更改为小于滚动视图的大小时自动调整 contentInset .

回复于 2024-04-27T20:42:01+08:00

一个优雅的方式来集中 UISCrollView 的内容就是这个 .

将一个观察者添加到 UIScrollView 的 contentSize 中，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];

现在用你的观察者方法：

- (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 .
同时更改指向窗口大小的 imageGallery .

这将在每次更改大小时更正内容的中心 .

NOTE: 这个内容不能很好地工作的唯一方法是使用 UIScrollView 的标准缩放功能 .

回复于 2024-04-27T20:42:01+08:00

这是我对该问题的解决方案，对于scrollview中的任何类型的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];
  }
}

回复于 2024-04-27T20:42:01+08:00

这里有很多解决方案，但我冒险把它放在这里 . 这有两个原因：它不会影响缩放体验，就像更新正在进行的图像视图帧一样，并且它还尊重原始滚动视图插图（例如，在xib或storyboard中定义，以便优雅地处理半透明工具栏等） .

首先，定义一个小帮手：

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;

在viewDidLoad中的某个地方填写它：

originalScrollViewInsets = self.scrollView.contentInset;

将UIImageView放入UIScrollView（假设UIImage本身位于loadedImage var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)
    );
}

我还没有测试方向改变（即调整UIScrollView本身的适当反应），但修复它应该相对容易 .

回复于 2024-04-27T20:42:01+08:00

23
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，您可能会两次调用此方法，但这是一个比本主题中的其他一些答案更清晰的解决方案 .
回复于 2024-04-27T20:42:01+08:00

Apple的Photo Scroller示例完全符合您的要求 . 将它放在您的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; 
}

Apple's Photo Scroller Sample Code

回复于 2024-04-27T20:42:01+08:00

25
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 UIView 提供与 UIScrollView 相同的宽高比，并将 UIImageView 置于其中心 .
回复于 2024-04-27T20:42:01+08:00

225

为了使动画流畅，请设置

self.scrollview.bouncesZoom = NO;

并使用此功能（使用this answer中的方法查找中心）

- (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，但不会事先涉及任何突然的动作 .

回复于 2024-04-27T20:42:01+08:00

只是swift中的已批准答案，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)
}

回复于 2024-04-27T20:42:01+08:00

1
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 only 放在缩小比其初始宽度小的位置，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
    }
  }
```
回复于 2024-04-27T20:42:01+08:00

这是我正在做这项工作的当前方式 . 它更好但仍然不完美 . 尝试设置：

myScrollView.bouncesZoom = YES;

修复 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];
}

此外，我执行以下操作以防止图像在缩小后粘在一侧 .

- (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
}

回复于 2024-04-27T20:42:01+08:00

好的，我想我找到了一个很好的解决方案 . 诀窍是不断重新调整 imageView's 帧 . 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];
}

回复于 2024-04-27T20:42:01+08:00

1
只是禁用分页，所以它会工作正常：
```
scrollview.pagingEnabled = NO;
```
回复于 2024-04-27T20:42:01+08:00

我有同样的问题 . 这是我如何解决的

应该将此代码作为 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);

回复于 2024-04-27T20:42:01+08:00

虽然这个问题有点陈旧但问题仍然存在 . 我在 Xcode 7 中通过将最上面的项目（在本例中为 topLabel ）的垂直空间约束设置为superViews（ scrollView ）顶部 IBOutlet 然后每次内容根据scrollView的子视图的高度更改时重新计算其常量来解决它（ 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()
    }
}

回复于 2024-04-27T20:42:01+08:00

UIScrollView的中心内容较小时

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