Swift 3 如何显示基于 MFMailComposeResult 电子邮件屏幕的确认屏幕

Question

我正在构建一个应用程序，用于构建电子邮件并将其显示在 MFMailComposeViewController 中供用户发送。当用户发送或取消它时，我希望应用程序以适当的确认屏幕消息进行响应。

我能够撰写电子邮件，关闭撰写屏幕，并且我在 IB 中有一个从预撰写 View 到确认 View 的命名 segue。但是我无法让那个 segue 执行。

那么，我怎样才能更新 segue 目标中的文本消息，然后继续到它。

因为我正在尝试学习 Swift，所以我对理解代码的工作原理非常感兴趣，而不仅仅是获得可以工作的代码。所以我真的很感激任何帮助。

工作流程从用户从应用中拍摄照片开始:

    func snapPhoto(){

    if let cameraConnection = sessionOutput.connection(withMediaType: AVMediaTypeVideo) {

        sessionOutput.captureStillImageAsynchronously(from: cameraConnection, completionHandler: { buffer, error in

            let myMessage   = self.buildEmail()
            let myJpg       = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(buffer)
            let mapSnap     = (self.myMap == nil) ? nil : UIImagePNGRepresentation(self.myMap!)

            let mail        = self.setupMail(to: myMessage.to, subject: myMessage.subject, body: myMessage.body, myJpg: myJpg!, mapSnap: mapSnap)

            self.presentMailComposer(mail: mail)

        }) // close completionHandler

    } // close if let cameraConnection

} // close func snapPhoto

它组装所有电子邮件内容并将其传递给:

    func presentMailComposer(mail : MFMailComposeViewController) {

    if MFMailComposeViewController.canSendMail() {

        self.present(mail, animated: true, completion: nil)

    } else {

        let sendMailErrorAlert = UIAlertController.init(title: "Uh oh!", message: "Unable to send email.", preferredStyle: .alert)
        self.present(sendMailErrorAlert, animated: true, completion: nil)

    } // close if

} // close presentEmailComposer

然后当用户点击“取消”的“发送”时触发

public func mailComposeController(_ controller: MFMailComposeViewController, didFinishWith result: MFMailComposeResult, error: Error?) {

    switch result.rawValue {

    case MFMailComposeResult.cancelled.rawValue:

        self.performSegue(withIdentifier: "afterEmail", sender: self)
        print("Mail cancelled")

    case MFMailComposeResult.saved.rawValue:

        print("Mail saved")

    case MFMailComposeResult.sent.rawValue:

        print("Mail sent")

    case MFMailComposeResult.failed.rawValue:

        print("Mail sent failure: %@", [error!.localizedDescription])

    default:

        break

    }

    controller.dismiss(animated: true, completion: nil)

} // close mailCompose

这就是我发现自己难住的地方。我可以访问 MFMailComposeResult，它是正确的，但我不知道如何呈现确认 View ，以便在撰写 View 滑开时它可用。

Answer 1

您需要使您的 View Controller 成为 MFMailComposeViewController 委托(delegate)并覆盖方法 didFinishWith 结果并在 dismiss 方法的完成处理程序中切换 MFMailComposeResult 值:

func mailComposeController(_ controller: MFMailComposeViewController, didFinishWith result: MFMailComposeResult, error: Error?) {
    controller.dismiss(animated: true) { 
        // do whatever you need to do after dismissing the mail window
        switch result {
            case .cancelled: print("cancelled")
            case .saved:     print("saved")
            case .sent:
                let alert = UIAlertController(title: "Mail Composer", message: "Mail was successfully sent", preferredStyle: .alert)
                alert.addAction(UIAlertAction(title: "Done", style: .default, handler: nil))
                self.present(alert, animated: true)
            case .failed:    print("failed")
        }
    }
}