java - 另一个 Java 事件问题

Question

所以我在 stackoverflow 上看到了多个问题，询问如何在 java 中实现事件，但似乎没有一个问题提供了“阅读此内容”之外的示例。

有人可以提供一个简洁的示例来说明如何实现以下 C# 代码的基本等效项吗？

public event EventHandler<MessageReceivedEventArgs> MessageReceived;
protected virtual void OnMessageReceived(Socket socket, CommandType commandType, MemoryStream message) 
{
    if (this.MessageReceived != null)
    {
        this.MessageReceived(this, new MessageReceivedEventArgs(socket, commandType, message));
    }
}

Answer 1

Java 中通常不使用多播委托(delegate)。如果不需要多播，那么代码如下:

public interface MessageReceivedListener {
    void onMessageReceived(Object sender, MessageReceivedEventArgs e);
}

private MessageReceivedListener messageReceivedListener;

public void setMessageReceivedListener(MessageReceivedListener listener) {
    this.messageReceivedListener = listener;
}

protected void onMessageReceived(Socket socket, CommandType commandType, MemoryStream message) {
    if (this.messageReceivedListener != null) {
        this.messageReceivedListener.onMessageReceived(this,
           new MessageReceivedEventArgs(socket, commandType, message));
    }
}

如果你想实现多播，那么你可以创建一个带有监听器的容器，迭代这些监听器并调用处理程序。在这种情况下，将有用于管理 Activity 监听器的 addMessageReceivedListener 和 removeMessageReceivedListener 方法。