UIImageView无法正确旋转？

Question

I have a UIScrollView inside a UIViewController. It has scrolling and zooming enabled. It contains a UIImageView and when the user rotates the device, the idea is that the image stays centered. The problem is, when the device is rotated, it actually appears off to the left instead of center, where it should be staying. Here is the code I'm using. Set frame is called when the UIScrollView rotates:

-(void)setFrame:(CGRect)frame {

    float previousWidth = self.frame.size.width;
    float newWidth = frame.size.width;

    [super setFrame:frame];
    self.imageView.center = CGPointMake(self.bounds.size.width / 2, self.bounds.size.height / 2);

    [self setupScales];

    self.zoomScale = self.zoomScale * (newWidth / previousWidth);
}

Answer 1

I use the following layoutsubviews method in my subclass of uiscrollview:

- (void)layoutSubviews {
    [super layoutSubviews];

    if ([[self subviews] count] == 0) {
        return;
    }

    // center the image as it becomes smaller than the size of the screen
    CGSize boundsSize = self.bounds.size;
    CGRect frameToCenter = ((UIView*)[[self subviews] objectAtIndex:0]).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;

    ((UIView*)[[self subviews] objectAtIndex:0]).frame = frameToCenter;
}

Answer 2

您可能还需要设置滚动视图的contentOffset属性

Answer 3

如果滚动视图的大小随着方向的改变而改变，请尝试以下操作

self.imageView.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleBottomMargin | UIViewAutoresizingFlexibleTopMargin;