ios - MFMessageComposeViewControllerDelegate 未被调用

Question

我正在尝试实现一个类，该类将呈现来自 AppDelegate 的 MFMessageComposeViewController。类声明如下所示:

import UIKit
import MessageUI

class MyClass: NSObject, MFMessageComposeViewControllerDelegate {

    func sendAMessage() {
        // message view controller
        let messageVC = MFMessageComposeViewController()
        messageVC.body = "Oh hai!"
        messageVC.recipients = ["8675309"]
        // set the delegate
        messageVC.messageComposeDelegate = self
        // present the message view controller
        UIApplication.sharedApplication().keyWindow?.rootViewController?.presentViewController(messageVC, animated: true, completion: nil)
    }

    // delegate implementation
    func messageComposeViewController(controller: MFMessageComposeViewController!, didFinishWithResult result: MessageComposeResult) {
        switch result.value {
        case MessageComposeResultCancelled.value:
            controller.presentingViewController?.dismissViewControllerAnimated(true, completion: nil)
        case MessageComposeResultFailed.value:
            controller.presentingViewController?.dismissViewControllerAnimated(true, completion: nil)
        case MessageComposeResultSent.value:
            controller.presentingViewController?.dismissViewControllerAnimated(true, completion: nil)
        default:
            break
        }
    }
}

在我的 AppDelegate 中，我在收到这样的推送通知后创建并调用 MyClass 的实例:

func application(application: UIApplication, didReceiveRemoteNotification userInfo: [NSObject : AnyObject], fetchCompletionHandler completionHandler: (UIBackgroundFetchResult) -> Void) {
    // instance of class
    let handler = MyClass()
    // call method
    handler.sendAMessage()
}

一开始一切正常——消息 View Controller 出现并且响应没有错误，但是每当按下发送或取消按钮时，消息 View Controller 不会关闭，屏幕变得无响应，委托(delegate) 未调用，我得到一个BAD_ACCESS错误。

如果我将 MFMessageComposeViewControllerDelegate 放入 AppDelegate 并设置 messageVC。 messageVC.messageComposeDelegate = UIApplication.sharedApplication().delegate as! MFMessageComposeViewControllerDelegate，然后一切正常， Controller 按预期关闭。

为什么 MFMessageComposeViewControllerDelegate 在 MyClass 对象中时未被调用？感谢阅读和帮助!

Answer 1

它正在崩溃，因为您的 handler 对象在调用 handler.sendMessage() 之后立即被释放和释放，然后现在尝试委托(delegate)回调 -当您尝试发送或点击取消时释放对象。该对象正在被释放和释放，因为在 application:didReceiveRemoteNotification: 结束时没有任何东西再持有对它的强引用。

由于您是在您的应用程序委托(delegate)中创建此对象，我建议您在您的应用程序委托(delegate)中创建一个属性来保存此对象:

var handler: MyClass?

func application(application: UIApplication, didReceiveRemoteNotification userInfo: [NSObject : AnyObject], fetchCompletionHandler completionHandler: (UIBackgroundFetchResult) -> Void) {
    // instance of class
    handler = MyClass()
    // call method
    handler?.sendAMessage()
}