我有一个框架，它具有在引发另一个类中的事件时更新框架的功能。我有“IRCClient”和“MainFrame”类。IRCClient 类有一个事件'OnMessageRecvd'，MainFrame 有一个函数'HandleNewMessageReceived'。在 MainFrame 类中，我有变量“CurrentServer”和“CurrentChannel”来指示当前向用户显示的服务器上的哪个频道。
现在，当我在按钮的回调中设置“CurrentServer”和“CurrentChannel”时，它们有一个值，一切都很好。但是，当 IRCClient 的 'OnMessageRecvd' 事件调用 'HandleNewMessageReceived' 函数时，CurrentServer 和 CurrentChannel 都等于 MainFrame 的构造函数中声明的任何值（null）。
有谁知道这种行为的根源是什么？提前非常感谢。
编辑：下面是代码，我只发布了有问题的代码（任何使用 CurrentChannel 和 CurrentServer 属性的函数）并剪掉了不相关的代码。
// Main page, shows chat history.
public sealed partial class MainPage : LIRC.Common.LayoutAwarePage
{
private uint maxMessages;
IRCClient ircc;
IRCHistory irch;
string CurrentServer, CurrentChannel;
// Does all the setup for this class.
public MainPage()
{
this.InitializeComponent();
ircc = App.ircc; // This is a global variable in the 'App' class.
ircc.OnMessage += NewMessageReceived;
irch = App.irch; // This is also a global variable in the 'App' class.
currentChannel = currentServer = null;
}
// Restores the previous state.
protected override void LoadState(Object navigationParameter, Dictionary<String, Object> pageState)
{
if (pageState != null)
{
if(pageState.ContainsKey("viewedChannel"))
{
// Retrieve required info.
string[] viewedChannelTokens = (pageState["viewedChannel"] as string).Split('.');
CurrentChannel = viewedChannelTokens[0];
CurrentServer = viewedChannelTokens[1];
// If the saved channel or server got corrupt
if (string.IsNullOrEmpty(CurrentChannel) || string.IsNullOrEmpty(CurrentServer))
{
// Check if a channel is open, if so, select it.
*snip* // Non-relevant code.
}
// Clear and load required history.
ClearHistory();
if(CurrentServer != null && CurrentChannel != null)
LoadHistory(CurrentServer, CurrentChannel);
}
}
// Create buttons that switch to a channel
*Snip* // Calls AddChannelButton
}
// Creates a button that, when clicked, causes the ChatHistoryView to display the ChannelHistory.
void AddChannelButton(string Server, string Channel)
{
Button btn = new Button();
btn.Content = Channel + "\n" + Server;
btn.Width = 150;
// A function to switch to another channel.
btn.Click += (e, s) =>
{
ClearHistory(); // Clears the ChatHistoryVi.ew field.
LoadHistory(Server, Channel); // Does the actual loading of the channel history
CurrentChannel = Channel;
CurrentServer = Server;
};
ChannelBar.Children.Add(btn);
}
// The function that is called by the IRCClient.OnMessageRecv event.
public void NewMessageReceived(ref DataWriter dw, IRCServerInfo ircsi, IRCClient.RecvMessage recvmsg)
{
if (ircsi.Name == CurrentServer && CurrentChannel == recvmsg.recipient)
{
AddMessage(DateTimeToTime(DateTime.UtcNow), recvmsg.author, recvmsg.message);
}
}
}
// Responsible for creating, managing and closing connections.
public class IRCClient
{
// A structure that describes a message.
public struct RecvMessage
{
public string author; // Nickname
public string realName;
public string ipAddress;
public string recipient; // Indicates in what channel or private converstion.
public string message; // The actual message
};
// Describes how a function that handles a message should be declared.
public delegate void MessageHandler(ref DataWriter dw, IRCServerInfo ircsi, RecvMessage msg);
// Gets raised/called whenever a message was received.
public event MessageHandler OnMessage;
}