单击警报按钮以显示MFMailComposeViewController [英] Click alert button to show MFMailComposeViewController

问题描述

在单击警报按钮时尝试使用MFMailComposeViewController.但是，当我单击警报按钮时，控制器不会弹出.代码如下.我使用了扩展程序，并在单击警报按钮时尝试调用sendmail函数.

Trying to use MFMailComposeViewController when click alert button. But when I click alert button, controller doesn't pop-up. The code is below. I used extension and I'm trying to call sendmail function when clicking alert button.

extension Alert:MFMailComposeViewControllerDelegate {
    func sendmail(){
        let mailComposeViewController = configureMailController()
        if MFMailComposeViewController.canSendMail() {
            let VC = storyboard?.instantiateViewController(withIdentifier: "MainVC")
            VC?.present(mailComposeViewController, animated: true, completion: nil)
        } else {
            showMailError()
        }
    }

    func configureMailController() -> MFMailComposeViewController {
        let mailComposerVC = MFMailComposeViewController()
        let VC = storyboard?.instantiateViewController(withIdentifier: "MainVC")
        mailComposerVC.mailComposeDelegate = VC as? MFMailComposeViewControllerDelegate

        mailComposerVC.setToRecipients(["**"])
        mailComposerVC.setSubject("**")
        mailComposerVC.setMessageBody("\n\n\n\nModel: \nSistem versiyon: )\nuygulamaversiyon:", isHTML: false)

        return mailComposerVC
    }

    func showMailError() {
        let sendMailErrorAlert = UIAlertController(title: "Could not send email", message: "Your device could not send email", preferredStyle: .alert)
        let dismiss = UIAlertAction(title: "Ok", style: .default, handler: nil)
        sendMailErrorAlert.addAction(dismiss)
        let VC = storyboard?.instantiateViewController(withIdentifier: "MainVC")
        VC?.present(sendMailErrorAlert, animated: true, completion: nil)
    }

    public func mailComposeController(_ controller: MFMailComposeViewController, didFinishWith result: MFMailComposeResult, error: Error?) {
        controller.dismiss(animated: true, completion: nil)
    }
}

推荐答案

您的代码尝试在您使用instantiateViewController创建的新视图控制器上呈现邮件视图控制器(以及错误警报).由于此新VC本身不是您应用程序VC层次结构的一部分，因此它和邮件VC都不会出现在屏幕上.

Your code tries to present the mail view controller (and also the error alert) on a new view controller which you create with instantiateViewController. Since this new VC itself is not part of your app's VC hierarchy, neither it nor the mail VC will appear on screen.

要实现此目的，您可以将 是应用程序一部分的视图控制器传递到您的sendmail方法中:

To make this work, you can either pass a view controller which is part of your app into your sendmail method:

func sendmail(_ root: UIViewController) {
  ...
  root.present(mailComposeViewController, animated: true, completion: nil)
  ...

或者您可以使用可全局访问的应用程序VC；在使用根VC的简单应用中应该可以工作:

Or you can use a globally accessible VC of your app; in a simple app using the root VC should work:

func sendmail() {
  ...
  let root = UIApplication.shared.keyWindow?.rootViewController
  root?.present(mailComposeViewController, animated: true, completion: nil)
  ...

我建议采用第一种方法，因为它更灵活(例如，即使您的VC层次结构变得更加复杂，它也允许您在任何地方打开邮件屏幕).

I'd suggest the first approach because it is more flexible (e.g. it allows you to open your mail screen anywhere, even when your VC hierarchy gets more complex).

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