我目前正在尝试用JDA编程一个非常基本的Discord机器人,而在将我的代码整齐地分为Main Class,MessageHandler
,CommandHandler
和VoiceHandler
时遇到了一个问题。类。
如果接收到事件,主类将添加一个EventListener来调用MessageHandler,如果在命令之前看到bot前缀,则分支到CommandHandler。
问题是,当尝试使用new CommandHandler.handleCmd
调用CommandHandler时,它将引发NullPointerException。错误消息显示为"ERROR JDA - One of the EventListeners had an uncaught exception"
,但是如果我没有记错的话,它应该做的只是分支到CommandHandler类的handleCmd函数中。所以我不明白为什么它会产生错误。
任何帮助将不胜感激!
这是我的主班
import net.dv8tion.jda.api.AccountType;
import net.dv8tion.jda.api.JDABuilder;
import net.dv8tion.jda.api.entities.Activity;
import net.dv8tion.jda.api.hooks.ListenerAdapter;
import javax.security.auth.login.LoginException;
public class Main extends ListenerAdapter {
public static void main(String[] args) throws LoginException {
JDABuilder builder = new JDABuilder(AccountType.BOT);
String token = "somethingsomething";
builder.setToken(token);
builder.addEventListeners(new MessageHandler()); //Puts Eventlistener to trigger MessageHandler
builder.build();
}
}
哪个应该触发我的MessageHandler
import net.dv8tion.jda.api.events.message.MessageReceivedEvent;
import net.dv8tion.jda.api.hooks.ListenerAdapter;
public class MessageHandler extends ListenerAdapter {
protected String userName;
protected String userMessage;
protected MessageReceivedEvent event;
public void onMessageReceived(MessageReceivedEvent event) {
userName = event.getAuthor().getName();
userMessage = event.getMessage().getContentRaw();
this.event = event;
if (event.getAuthor().isBot()) {
return;
} else if (userMessage.startsWith(">")) {
new CommandHandler().handleCmd(); //Should trigger CommandHandler (this is the problem)
}
}
}
然后分支到CommandHandler
public class CommandHandler extends MessageHandler {
private String command = userMessage.substring(1);
public void handleCmd() {
switch (command) {
case "join":
new VoiceHandler().join();
break;
case ... :
...
break;
case ... :
...
break;
}
}
}
[VoiceHandler.join()方法仅使漫游器连接到我的语音通道,但现在暂时不相关
如果有帮助,这也是完整的错误消息
[JDA MainWS-ReadThread] ERROR JDA - One of the EventListeners had an uncaught exception
java.lang.NullPointerException
at CommandHandler.<init>(CommandHandler.java:2)
at MessageHandler.onMessageReceived(MessageHandler.java:17)
at net.dv8tion.jda.api.hooks.ListenerAdapter.onEvent(ListenerAdapter.java:376)
at net.dv8tion.jda.api.hooks.InterfacedEventManager.handle(InterfacedEventManager.java:96)
at net.dv8tion.jda.internal.hooks.EventManagerProxy.handle(EventManagerProxy.java:64)
at net.dv8tion.jda.internal.JDAImpl.handleEvent(JDAImpl.java:151)
at net.dv8tion.jda.internal.handle.MessageCreateHandler.handleInternally(MessageCreateHandler.java:122)
at net.dv8tion.jda.internal.handle.SocketHandler.handle(SocketHandler.java:36)
at net.dv8tion.jda.internal.requests.WebSocketClient.onDispatch(WebSocketClient.java:853)
at net.dv8tion.jda.internal.requests.WebSocketClient.onEvent(WebSocketClient.java:741)
at net.dv8tion.jda.internal.requests.WebSocketClient.handleEvent(WebSocketClient.java:720)
at net.dv8tion.jda.internal.requests.WebSocketClient.onBinaryMessage(WebSocketClient.java:891)
at com.neovisionaries.ws.client.ListenerManager.callOnBinaryMessage(ListenerManager.java:385)
at com.neovisionaries.ws.client.ReadingThread.callOnBinaryMessage(ReadingThread.java:276)
at com.neovisionaries.ws.client.ReadingThread.handleBinaryFrame(ReadingThread.java:996)
at com.neovisionaries.ws.client.ReadingThread.handleFrame(ReadingThread.java:755)
at com.neovisionaries.ws.client.ReadingThread.main(ReadingThread.java:108)
at com.neovisionaries.ws.client.ReadingThread.runMain(ReadingThread.java:64)
at com.neovisionaries.ws.client.WebSocketThread.run(WebSocketThread.java:45)
stacktrace会告诉您异常发生在哪一行(CommandHandler
的第2行)。
您的字段userMessage
为null
,您正在对其执行方法调用。如果尚未在CommandHandler中设置userMessage
,则会发生这种情况。