使用Swift 4 / iOS 10.3，您可以选择以下方式之一来解决您的问题。

1.拍摄视图控制器视图的屏幕截图

以下代码显示如何拍摄屏幕截图并将其保存在设备相册中：

import UIKit

class ViewController: UIViewController {

    /* ... */

    @IBAction func screenshot(_ sender: UIBarButtonItem) {
        //Create the UIImage
        UIGraphicsBeginImageContextWithOptions(view.frame.size, true, 0)
        guard let context = UIGraphicsGetCurrentContext() else { return }
        view.layer.render(in: context)
        guard let image = UIGraphicsGetImageFromCurrentImageContext() else { return }
        UIGraphicsEndImageContext()

        //Save it to the camera roll
        UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil)
    }

}

请注意，此代码的结果将是.JPG图像。另请注意，导航栏和状态栏不会出现在最终图像中。

从iOS 10开始，作为以前代码的替代方法，您可以使用以下代码：

import UIKit

class ViewController: UIViewController {

    /* ... */

    @IBAction func screenshot(_ sender: UIBarButtonItem) {
        //Create the UIImage
        let renderer = UIGraphicsImageRenderer(size: view.frame.size)
        let image = renderer.image(actions: { context in
            view.layer.render(in: context.cgContext)
        })

        //Save it to the camera roll
        UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil)
    }

}

2.拍摄iPhone窗口的屏幕截图

如果要截取包含导航栏（但不包括状态栏）的屏幕截图，则可以使用以下代码：

import UIKit

class ViewController: UIViewController {

    /* ... */

    @IBAction func screenshot(_ sender: UIBarButtonItem) {
        //Create the UIImage
        guard let layer = UIApplication.shared.keyWindow?.layer else { return }
        UIGraphicsBeginImageContextWithOptions(layer.frame.size, true, 0)
        guard let context = UIGraphicsGetCurrentContext() else { return }
        layer.render(in: context)
        guard let image = UIGraphicsGetImageFromCurrentImageContext() else { return }
        UIGraphicsEndImageContext()

        //Save it to the camera roll
        UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil)
    }

}

从iOS 10开始，作为以前代码的替代方法，您可以使用以下代码：

import UIKit

class ViewController: UIViewController {

    /* ... */

    @IBAction func screenshot(_ sender: UIBarButtonItem) {
        //Create the UIImage
        guard let layer = UIApplication.shared.keyWindow?.layer else { return }
        let renderer = UIGraphicsImageRenderer(size: layer.frame.size)
        let image = renderer.image(actions: { context in
            layer.render(in: context.cgContext)
        })

        //Save it to the camera roll
        UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil)
    }

}

提醒

从iOS
10开始，为了防止您的应用在调用screenshot(_:)方法时崩溃，您需要将密钥添加NSPhotoLibraryUsageDescription到项目的Info.plist文件中：

<key>NSPhotoLibraryUsageDescription</key>
<string>Some description to explain why access is required</string>