我的 JavaFX 服务器客户端聊天项目不断出现空指针错误

Question

大家好，我最近一直在开发服务器和客户端聊天程序，但是我无法从控制器类访问 Main 类，即使它已经在 start 方法中设置和初始化。

package application;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class Main extends Application {

    private Client client = new Client(1234);

    @Override
    public void start(Stage primaryStage) throws Exception {

        FXMLLoader loader = new FXMLLoader(getClass().getResource("LogInPage.fxml"));
        Parent root = loader.load();

        ChatController controller = loader.getController();
;

        Scene scene = new Scene(root);

        primaryStage.setScene(scene);
        primaryStage.show();


        
    }

    public static void main(String[] args) {
        launch(args);
    }

    public Client getClient() {
        return client;
    }

    public void setClient(Client client) {
        this.client = client;
    }

}

package application;

import java.io.IOException;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextArea;
import javafx.scene.control.TextField;
import server.Server;

public class ChatController {
    @FXML private TextField myTextField;
    @FXML private Button button;
    @FXML private TextArea textArea;
    @FXML private TextField emailField;
    @FXML private PasswordField passwordField;
    @FXML private Button signUpButton;
    private Main main;
    
    
    
    public void setMain(Main main) {
        this.main = main;
    }
    
    public void onSendButton(ActionEvent e) {

        main.getClient().sendMessage(myTextField.getText());
        setTextArea(myTextField.getText());

        myTextField.setText("");
    }

    public void setTextArea(String readLine) {

        textArea.setText(readLine + "\n");

    }

    public void onSignIn(ActionEvent e) throws IOException {

        if (Server.getSql().getUser().logIn(emailField.getText(), passwordField.getText()) == true) {

            FXMLLoader loader = new FXMLLoader(getClass().getResource("ChatUI.fxml"));
            Parent root = loader.load();

            Scene scene = emailField.getScene();

            scene.setRoot(root);

        }

    }

}

package application;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.lang.ModuleLayer.Controller;
import java.net.Socket;

public class Client implements Runnable {

    private Socket socket; // socket to connect to
    private int port; // port number for the server
    private PrintWriter out; // output stream for the server
    private BufferedReader in; // input stream for the server
    private ChatController controller;

    /**
     * A constructor for the client
     * 
     * @param port - the port number for the server
     */
    public Client(int port) {
        this.port = port;
        try {
            this.socket = new Socket("localhost", this.port);
            out = new PrintWriter(socket.getOutputStream(), true);
            in = new BufferedReader(new InputStreamReader(this.socket.getInputStream()));

        } catch (IOException e) {
            e.printStackTrace();
            System.exit(0);
        }

        Thread thread = new Thread(this);
        thread.start();

    }

    public void setController(ChatController controller2) {
        this.controller = controller2;
    }

    /**
     * Requests and sends message to the server
     */
    public void sendMessage(String message) {
        out.println(message);

    }

    @Override
    /**
     * Reads incoming messages from the server
     */
    public void run() {

        while (true) {
            try {
                controller.setTextArea(in.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }

}

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml/javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1857)
    at javafx.fxml/javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1724)
    at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:234)
    at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
    at javafx.graphics/javafx.scene.Node.fireEvent(Node.java:8792)
    at javafx.controls/javafx.scene.control.Button.fire(Button.java:203)
    at javafx.controls/com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:208)
    at javafx.controls/com.sun.javafx.scene.control.inputmap.InputMap.handle(InputMap.java:274)
    at javafx.base/com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:247)
    at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:234)
    at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
    at javafx.graphics/javafx.scene.Scene$MouseHandler.process(Scene.java:3897)
    at javafx.graphics/javafx.scene.Scene.processMouseEvent(Scene.java:1878)
    at javafx.graphics/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2623)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:411)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:301)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:450)
    at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:424)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:449)
    at javafx.graphics/com.sun.glass.ui.View.handleMouseEvent(View.java:557)
    at javafx.graphics/com.sun.glass.ui.View.notifyMouse(View.java:943)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:184)
    at java.base/java.lang.Thread.run(Thread.java:831)
Caused by: java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at com.sun.javafx.reflect.Trampoline.invoke(MethodUtil.java:77)
    at jdk.internal.reflect.GeneratedMethodAccessor2.invoke(Unknown Source)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at javafx.base/com.sun.javafx.reflect.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml/com.sun.javafx.fxml.MethodHelper.invoke(MethodHelper.java:84)
    at javafx.fxml/javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1852)
    ... 46 more
Caused by: java.lang.NullPointerException: Cannot invoke "application.Main.getClient()" because "this.main" is null
    at Chat/application.ChatController.onSendButton(ChatController.java:33)
    ... 57 more

我尝试了各种方法，例如在控制器类中添加 setMain 方法我试图将所有内容都放在主类中，但我一直为 textArea 获取空指针我不确定发生了什么。