尝试创建一个屏幕截图按钮，当单击该按钮时，该按钮会将屏幕截图发送到我的相机胶卷中。Swift 3、Xcode 8、IOS

import UIKit

class ViewController: UIViewController {
    
    @IBAction func captureScreen(_ sender: UIButton) {
        let screenBounds = UIScreen.main.bounds
        
        UIGraphicsBeginImageContextWithOptions(screenBounds.size, false, 0)
        guard let context = UIGraphicsGetCurrentContext() else { return }
        
        for window in UIApplication.shared.windows {
            window.layer.render(in: context)
        }
        
        guard let screenshot = UIGraphicsGetImageFromCurrentImageContext() else { return }
        UIGraphicsEndImageContext()
        
        UIImageWriteToSavedPhotosAlbum(screenshot, nil, nil, nil)
    }
}