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我一直在为这个问题苦苦挣扎一段时间，似乎没有明确的答案。请让我知道是否有人知道这一点。

我想在屏幕中央显示一张照片UIScrollView（图像可能是纵向或横向）。

我希望能够像在照片应用程序中那样仅将图像缩放和平移到图像的边缘。

我已经尝试过改变contentInsetinviewDidEndZooming方法，这样就可以了，但是有几个小故障。

我还尝试制作与图像imageView相同的大小scrollView并将图像居中。问题是，当您缩放时，您可以滚动整个imageView图像，而部分图像可能会滚动到视图之外。

我在这里找到了一个类似的帖子并给出了我最好的解决方法，但没有找到真正的答案：

具有居中 UIImageView 的 UIScrollView，如照片应用

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3 回答 3

2

一种将内容居中的优雅方式UISCrollView是这样。

将一个观察者添加到您的contentSize中UIScrollView，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 ); }

  • 你应该改变[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。

每次他的大小改变时，这将纠正内容的中心。

注意：此内容不能很好地工作的唯一方法是使用UIScrollView.

于 2009-11-03T17:26:39.157 回答
2

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 PhotoScroll 应用程序的 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;
}
于 2010-08-13T16:54:32.410 回答
1

这是我能为这个问题想出的最佳解决方案。诀窍是不断地重新调整 imageView 的框架。我发现这比不断调整 contentInsets 或 contentOffSets 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。

如果有人能想出更好的方法来做到这一点，我很想听听。

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];
}

这是我在 viewDidLoad 方法中计算最小缩放比例的方法。

CGSize photoSize = [temporaryImage size];
CGSize screenSize = [[self view] bounds].size;

CGFloat widthRatio = screenSize.width / photoSize.width;
CGFloat heightRatio = screenSize.height / photoSize.height;
initialZoom = (widthRatio > heightRatio) ? heightRatio : widthRatio;
[myScrollView setMinimumZoomScale:initialZoom];
[myScrollView setZoomScale:initialZoom];
[myScrollView setMaximumZoomScale:3.0];
于 2009-10-04T02:19:14.517 回答