iOS share method for sharing a file through Flutter's platform channel using UIActivityViewController

AppDelegatePart.swift

func shareFile(arguments:Any?) -> Void {
    let argsMap = arguments as! NSDictionary
    
    let subject = argsMap.value(forKey: "subject") as? String
    let filepath = argsMap.value(forKey: "filepath") as? String
    let x = argsMap.value(forKey: "x") as? NSNumber
    let y = argsMap.value(forKey: "y") as? NSNumber
    let width = argsMap.value(forKey: "width") as? NSNumber
    let height = argsMap.value(forKey: "height") as? NSNumber
    
    // Add shareable activity items
    var activityItems:[Any] = [];
    
    if let path = filepath {
        activityItems.append(NSURL(fileURLWithPath: path))
    }
    
    if let title = subject, !title.isEmpty {
        activityItems.append(title);
    }
    
    // Set up activity view controller
    let controller = UIApplication.shared.keyWindow!.rootViewController as! FlutterViewController
    let activityViewController:UIActivityViewController = UIActivityViewController(activityItems: activityItems, applicationActivities: nil)
    activityViewController.popoverPresentationController?.sourceView = controller.view

    // Present the view controller indicating the share action origin
    if let posX = x, let posY = y, let width = width, let height = height {
        let sourceRect = CGRect(x: posX.doubleValue, y: posY.doubleValue, width: width.doubleValue, height: height.doubleValue)
        activityViewController.popoverPresentationController?.sourceRect = sourceRect
    }
    
    controller.show(activityViewController, sender: self)
}