swift-不能使用AutoLayout在UIScrollView中居中UIImageView

Question

找遍了对多篇UIScrollView与UIImageView中,但都没有AutoLayout信息.我所做的是:地方UIScrollView在UIViewController与约束前10名,领先的10,底部50,落后10; 放置UIImageView在UIScrollView约束前面0,前面0,下面0,尾随0.我想要的很简单:让我的UIImageView适合我的UIScrollView应用程序第一次加载时,让我的UIImageView水平和垂直居中.现在我可以看到图像并恰好适合屏幕,但图像位于顶部UIScrollView.(注意:在这种情况下,我的图像宽度在缩放到最小值后zoomScale等于宽度UIScrollView,我的图像高度在缩放到最小值zoomScale小于宽度之后UIScrollView.)我真的无法将我移动UIImageView到UIScrollView垂直中心,无法找到我发生错误的地方.非常感谢.

import UIKit
class ViewController: UIViewController, UIScrollViewDelegate {
@IBOutlet weak var scrollView: UIScrollView!
@IBOutlet weak var imageView: UIImageView!
override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}
func centerScrollViewContents() {
    let boundsSize = scrollView.bounds.size
    var contentsFrame = imageView.frame
    if contentsFrame.size.width < boundsSize.width {
        contentsFrame.origin.x = (boundsSize.width - contentsFrame.size.width) / 2.0
    } else {
        contentsFrame.origin.x = 0.0
    }

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

override func viewDidLayoutSubviews() {
    let myImage = UIImage(named: "7.jpg")
    imageView.image = myImage        
    let weightScale = scrollView.bounds.size.width / myImage!.size.width
    let heightScale = scrollView.bounds.size.height / myImage!.size.height
    let minScale = min(weightScale, heightScale)
    let imagew = myImage!.size.width * minScale
    let imageH = myImage!.size.height * minScale
    let imageRect = CGRectMake(0, 0, imagew, imageH)
    imageView.frame = imageRect
    scrollView.contentSize = myImage!.size
    scrollView.maximumZoomScale = 1.0
    scrollView.minimumZoomScale = minScale
    scrollView.zoomScale = minScale
    imageView.frame = imageRect
    centerScrollViewContents()
}
func viewForZoomingInScrollView(scrollView: UIScrollView) -> UIView? {
    return imageView
}

}

Answer 1

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
    }