如何制作Scrollview所有内容的屏幕截图? [英] How to make a screenshot of all the content of a Scrollview?

问题描述

我想创建一个UIScrollView的屏幕截图，其中应包含滚动视图的全部内容，甚至包括该内容当前对用户不可见.为此，我尝试了以下两种方法:

I want to create a screenshot of a UIScrollView which should contain the whole content of the scroll view, even that content, which is currently not visible to the user. For that I tried the following two methods:

func snapShot(view:UIView) -> UIImage {
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, true, 0);

    view.drawViewHierarchyInRect(view.bounds, afterScreenUpdates: true);

    let image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return image;
}

func snapShotScrollView(scrollView:UIScrollView) -> UIImage {
    let bounds = scrollView.bounds;

    scrollView.bounds.size = scrollView.contentSize;

    let image = snapShot(scrollView);

    scrollView.bounds = bounds;

    return image;
}

但是生成的图像仍仅显示了滚动视图内用户当前可见的那些视图元素.但我想查看所有视图.

But the resulting image is still just showing those view elements inside the scroll view which are currently visible to the user. But I want to see all views.

我该怎么做?

编辑

我也尝试过:

func snapshot() -> UIImage? {
    var image: UIImage?

    UIGraphicsBeginImageContext(scrollView.contentSize)

    let savedContentOffset = scrollView.contentOffset
    let savedFrame = scrollView.frame;

    scrollView.contentOffset = CGPoint.zero;
    scrollView.frame = CGRect(x: 0, y: 0, width: scrollView.contentSize.width, height: scrollView.contentSize.height);

    scrollView.layer.render(in: UIGraphicsGetCurrentContext()!)
    image = UIGraphicsGetImageFromCurrentImageContext();

    scrollView.contentOffset = savedContentOffset;
    scrollView.frame = savedFrame;

    UIGraphicsEndImageContext();

    return image
}

编辑2

我的UIScrollView放在UIView内，并且确实包含UIStackView.该视图被设计为弹出视图，因此看起来就像弹出对话框一样.我第一次编辑的代码示例在空白的UIViewController中工作，只有一个UIScrollView，但在上述的星座图中却没有.

My UIScrollView is placed inside a UIView and does contain a UIStackView. The View is designed as a popover view so that it looks like a dialogue is popping up. The code sample from my first edit is working in a blank UIViewController with only one UIScrollView but not in the mentioned constellation.

推荐答案

从此答案到Swift，并添加了测试ViewController:

To Swift from this answer, adding a test ViewController:

class ScreenShotTestViewController: UIViewController {

    var scrollView: UIScrollView!

    override func viewDidLoad() {
        super.viewDidLoad()
        scrollView = UIScrollView(frame: CGRect(origin: CGPoint.zero, size: view.frame.size))
        scrollView.contentSize = CGSize(width: view.frame.size.width, height: view.frame.size.height * 2)
        scrollView.backgroundColor = UIColor.yellow
        view.addSubview(scrollView)

        let label = UILabel(frame: CGRect(x: 0.0, y: view.frame.size.height * 1.5, width: view.frame.size.width, height: 44.0))
        label.text = "Hello World!"
        scrollView.addSubview(label)

        let screenShot = snapshot()
    }

    func snapshot() -> UIImage?
    {      
        UIGraphicsBeginImageContext(scrollView.contentSize)

        let savedContentOffset = scrollView.contentOffset
        let savedFrame = scrollView.frame

        scrollView.contentOffset = CGPoint.zero
        scrollView.frame = CGRect(x: 0, y: 0, width: scrollView.contentSize.width, height: scrollView.contentSize.height)

        scrollView.layer.render(in: UIGraphicsGetCurrentContext()!)
        let image = UIGraphicsGetImageFromCurrentImageContext()

        scrollView.contentOffset = savedContentOffset
        scrollView.frame = savedFrame

        UIGraphicsEndImageContext()

        return image
    }
}

生成包含子视图的完整内容的图像:

Results in an image of the complete content, including subviews:

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