Objective c 如何在ScrollView中居中显示UIImageView（缩放）

我正在尝试在

UIScrollView

中缩放UIImageView。我有这个：

-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
return imageView;
}

-(void)scrollViewDidZoom:(UIScrollView *)scrollView {
[imageView setCenter:CGPointMake(scrollView.center.x, scrollView.center.y)];
}

-(void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale {
}

问题是：当我缩小图像时，它是居中的，但当我放大时，图像会移到左上角

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我的代码哪里有问题？

答案是从

scrollViewDidZoom:

中删除所有内容并添加：

[self centerScrollViewContent];

方法实现：

- (void)centerScrollViewContents {
CGSize boundsSize = self.scrollView.bounds.size;
CGRect contentsFrame = self.containerView.frame;

if (contentsFrame.size.width < boundsSize.width) {
    contentsFrame.origin.x = (boundsSize.width - contentsFrame.size.width) / 2.0f;
} else {
    contentsFrame.origin.x = 0.0f;
}

if (contentsFrame.size.height < boundsSize.height) {
    contentsFrame.origin.y = (boundsSize.height - contentsFrame.size.height) / 2.0f;
} else {
    contentsFrame.origin.y = 0.0f;
}

self.containerView.frame = contentsFrame;
}

-（无效）centerScrollViewContents{
CGSize boundsSize=self.scrollView.bounds.size；
CGRect contentsFrame=self.containerView.frame；
if（contentsFrame.size.width

答案是从scrollViewDidZoom:中删除所有内容并添加：

[self centerScrollViewContent];

方法实现：

- (void)centerScrollViewContents {
CGSize boundsSize = self.scrollView.bounds.size;
CGRect contentsFrame = self.containerView.frame;

if (contentsFrame.size.width < boundsSize.width) {
    contentsFrame.origin.x = (boundsSize.width - contentsFrame.size.width) / 2.0f;
} else {
    contentsFrame.origin.x = 0.0f;
}

if (contentsFrame.size.height < boundsSize.height) {
    contentsFrame.origin.y = (boundsSize.height - contentsFrame.size.height) / 2.0f;
} else {
    contentsFrame.origin.y = 0.0f;
}

self.containerView.frame = contentsFrame;
}

-（无效）centerScrollViewContents{
CGSize boundsSize=self.scrollView.bounds.size；
CGRect contentsFrame=self.containerView.frame；
if（contentsFrame.size.width