swift-不能使用AutoLayout在UIScrollView中居中UIImageView

小猪支持pic-o-matic的回答.我有一个案例,我需要将图像居中,只要它小于滚动视图框架.使用插图为简单的解决方案.

if imageView.frame.height <= scrollView.frame.height {
        let shiftHeight = scrollView.frame.height/2.0 - scrollView.contentSize.height/2.0
        scrollView.contentInset.top = shiftHeight
    }
    if imageView.frame.width <= scrollView.frame.width {
        let shiftWidth = scrollView.frame.width/2.0 - scrollView.contentSize.width/2.0
        scrollView.contentInset.left = shiftWidth
    }