C# 订阅服务器的onNext操作未在ViewDidLoad中激发，但在同一类中激发

我正在使用Xamarin.iOS开发一个聊天移动应用程序

我有一个名为MessageServices的类，它发出事件MessageAddedToDB

我有一个名为Services的类，我在其中初始化MessageServices类

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public MessageServices messageService;

public IObservable<ChatMessage> receivedMessageObservable;
public IObservable<ChatMessage> messageSuccessfullySentObservable;

public Services()
{
    messageService = new MessageServices();
    messageService.MessageAddedToDB += (message) =>
    {
        Debug.WriteLine(message.Message); //This gets fired
    }


   AddObservables();
}

public void AddObservables()
{
    receivedMessageObservable = Observable.FromEvent<MessageAddedToDBEventHandler, ChatMessage>(
    (handler) =>
    {
        MessageAddedToDBEventHandler messageAddedToDBEventHandler = (ChatMessage m) =>
        {
            handler(m);
        };
        return messageAddedToDBEventHandler;
    },
    ev => messageService.MessageAddedToDB += ev,
    ev => messageService.MessageAddedToDB -= ev);

    receivedMessageObservable.Subscribe(onNext: (m) =>
    {
        Debug.WriteLine(m.Message); // This gets fired
    }

    messageSuccessfullySentObservable = Observable.FromEvent<MessageSuccessfullySentEventHandler, ChatMessage>
        (
            (handler) =>
            {
                MessageSuccessfullySentEventHandler messageSuccessfullySentEventHandler = (ChatMessage m) =>
                {
                    handler(m);
                };

                return messageSuccessfullySentEventHandler;
            },
            ev => httpHandler.MessageSuccessfullySent += ev,
            ev => httpHandler.MessageSuccessfullySent -= ev
        );
}

---

我在Services类中还有其他可观察对象，比如messageSuccessfullySentObservable，在这里我以与receivedMessageObservable相同的方式初始化它们。ViewController中的订阅服务器的初始化方式与我对receivedMessageSubscriber的初始化方式相同。其他订阅者的行为将被解雇。

您的代码工作得非常好。试试这个：

void Main()
{
    var messageService = new MessageService();

    var messageReceivedObservable = Observable.FromEvent<MessageAddedToDBEventHandler, ChatMessage>(
        handler =>
        {
            MessageAddedToDBEventHandler messageAddedToDBEventHandler = (ChatMessage m) =>
            {
                handler(m);
                return m;
            };
            return messageAddedToDBEventHandler;
        },
        ev => messageService.MessageAddedToDB += ev,
        ev => messageService.MessageAddedToDB -= ev
    );

    messageReceivedObservable
    .Subscribe((message) =>
    {
        Console.WriteLine(message);
    });         

    messageService.Raise();
    messageService.Raise();
}

public delegate ChatMessage MessageAddedToDBEventHandler(ChatMessage m);

public class MessageService
{
    public event MessageAddedToDBEventHandler MessageAddedToDB;
    public void Raise()
    {
        this.MessageAddedToDB?.Invoke(new ChatMessage());
    }
}

public class ChatMessage { }

---

你的代码中一定有你没有展示给我们的东西。

你是说从未调用subscribe方法，还是说从未调用subscribe委托？@Enigmativity我的意思是从未调用subscribe委托没有IDisposable这样的类型。这不是真正的代码。你只调用过一个新的MessageServices和一个新的Services吗？@Enigmativity你是对的，我发现Services类有两个不同的实例，触发messageService事件的类没有订阅可观察对象，所以我创建了一个静态Services类，它成功了。非常感谢您的时间我不知道我已经尝试添加了普通的EventHandler，代理被调用，但是subscribe方法的操作没有被调用我在一个单独的项目上尝试了您的代码，您是对的，它可以工作@Enigmativity@husamdev-然后是您的messageService没有引发事件。我使用+=，添加了一个普通的事件处理程序，并调用了它。实际上，在同一个类中，订阅者的onNext会被调用，但在另一个类中则不会@Enigmativity@husamdev-你需要一份能证明你的问题的报告。

void Main()
{
    var messageService = new MessageService();

    var messageReceivedObservable = Observable.FromEvent<MessageAddedToDBEventHandler, ChatMessage>(
        handler =>
        {
            MessageAddedToDBEventHandler messageAddedToDBEventHandler = (ChatMessage m) =>
            {
                handler(m);
                return m;
            };
            return messageAddedToDBEventHandler;
        },
        ev => messageService.MessageAddedToDB += ev,
        ev => messageService.MessageAddedToDB -= ev
    );

    messageReceivedObservable
    .Subscribe((message) =>
    {
        Console.WriteLine(message);
    });         

    messageService.Raise();
    messageService.Raise();
}

public delegate ChatMessage MessageAddedToDBEventHandler(ChatMessage m);

public class MessageService
{
    public event MessageAddedToDBEventHandler MessageAddedToDB;
    public void Raise()
    {
        this.MessageAddedToDB?.Invoke(new ChatMessage());
    }
}

public class ChatMessage { }