Ios UIScrollView内容未缩放

我在UIScrollview中有一个UIImageView，当我尝试收缩和缩放时，图像会向下和向右跳跃（我认为是坐标0,0而不是居中），但保持相同的大小和位置，直到我停止收缩，然后它会弹回到以前居中的状态

我让NSLog在缩放时打印出缩放比例，然后一直打印0.5，直到我放开，然后它打印1.0一次

我真的很茫然，所有关于这方面的教程看起来都很简单，我不知道哪里出了问题

注:

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scrollView和ImageView都位于故事板中，连接到插座。它们所在的viewController是实现viewForZoomingInScrollView:的UIScrollView委托。minimumScale为1.0，maximumScale为4.0，尽管这些数字似乎没有任何影响。

将此代码放入viewDidLoad

yourScroll.bouncesZoom = YES;
yourScroll.delegate = self;
yourScroll.clipsToBounds = YES;

UITapGestureRecognizer *twoFingerTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTwoFingerTap:)];

[twoFingerTap setNumberOfTouchesRequired:2];

[yourImageView addGestureRecognizer:twoFingerTap];

float minimumScale = 1.0;//This is the minimum scale, set it to whatever you want. 1.0 = default

yourScroll.maximumZoomScale = 4.0;
yourScroll.minimumZoomScale = minimumScale;
yourScroll.zoomScale = minimumScale;
[yourScroll setContentMode:UIViewContentModeScaleAspectFit];
[yourScroll sizeToFit];
[yourScroll setContentSize:CGSizeMake(yourImageView.frame.size.width, yourImageView.frame.size.height)];

添加Scrollview和手势的代理方法

#pragma mark UIScrollViewDelegate methods

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {

    return yourImageView;
}

#pragma mark TapDetectingImageViewDelegate methods

- (void)scrollViewDidZoom:(UIScrollView *)aScrollView {
    CGFloat offsetX = (yourScroll.bounds.size.width > yourScroll.contentSize.width)?
    (yourScroll.bounds.size.width - yourScroll.contentSize.width) * 0.5 : 0.0;
    CGFloat offsetY = (yourScroll.bounds.size.height > yourScroll.contentSize.height)?
    (yourScroll.bounds.size.height - yourScroll.contentSize.height) * 0.5 : 0.0;
    yourImageView.center = CGPointMake(yourScroll.contentSize.width * 0.5 + offsetX,
                                       yourScroll.contentSize.height * 0.5 + offsetY);
}


- (void)handleTwoFingerTap:(UIGestureRecognizer *)gestureRecognizer {
    // two-finger tap zooms out
    float newScale = [previewScroll zoomScale] / ZOOM_STEP;
    CGRect zoomRect = [self zoomRectForScale:newScale withCenter:[gestureRecognizer locationInView:gestureRecognizer.view]];
    [yourScroll zoomToRect:zoomRect animated:YES];
}

#pragma mark Utility methods

- (CGRect)zoomRectForScale:(float)scale withCenter:(CGPoint)center {

    CGRect zoomRect;

    // the zoom rect is in the content view's coordinates.
    //    At a zoom scale of 1.0, it would be the size of the imageScrollView's bounds.
    //    As the zoom scale decreases, so more content is visible, the size of the rect grows.
    zoomRect.size.height = [previewScroll frame].size.height / scale;
    zoomRect.size.width  = [previewScroll frame].size.width  / scale;

    // choose an origin so as to get the right center.
    zoomRect.origin.x    = center.x - (zoomRect.size.width  / 2.0);
    zoomRect.origin.y    = center.y - (zoomRect.size.height / 2.0);

    return zoomRect;
}

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感谢iOS10，该文档看起来非常直接和简单，但为什么它对我不起作用？我设置了委托，并实现了viewForZoomingInScrollView:，还有什么要做的呢？这对以编程方式实现这一点很有帮助，但是每个教程（包括Apple自己的文档）都说，我只需要在代码方面实现viewForZoomingInScrollView