JavaFX 访问错误，不确定是什么原因造成的

Question

这是我的代码(我删除了很多图形逻辑，看看它是否会运行一个最基本的文件)

import java.util.Scanner;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;
import java.util.Scanner;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
class Client extends Application {
public static String host = "127.0.0.1";
public BufferedReader fromServer;
public PrintWriter toServer;
public Scanner consoleInput = new Scanner(System.in);
public Client() {
}

public static void main(String[] args) {
launch(args);
}
public void start(Stage displayStage) {     
try {
System.out.println("HELLO");
} catch (Exception e) {
System.err.println("Client connection error!"); 
e.printStackTrace();
}
}
}

但是错误信息真的很奇怪，我不确定它到底是什么意思;它提到了一个公共访问，但恐怕，公共意味着任何东西都可以访问它，我不使用反射，但它抛出了关于反射的错误，我真的很困惑，什么可能导致这个错误。

Exception in Application constructor
Exception in thread "main" java.lang.reflect.InvocationTargetException
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1071)
Caused by: java.lang.RuntimeException: Unable to construct Application instance: class eHillsClient.Client
at javafx.graphics@18/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:891)
at javafx.graphics@18/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:196)
at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: java.lang.IllegalAccessException: class com.sun.javafx.application.LauncherImpl (in module javafx.graphics) cannot access a member of class eHillsClient.Client with modifiers "public"
at java.base/jdk.internal.reflect.Reflection.newIllegalAccessException(Reflection.java:392)
at java.base/java.lang.reflect.AccessibleObject.checkAccess(AccessibleObject.java:674)
at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:489)
at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:480)
at javafx.graphics@18/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$8(LauncherImpl.java:803)
at javafx.graphics@18/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:484)
at javafx.graphics@18/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:457)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
at javafx.graphics@18/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:456)
at javafx.graphics@18/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
at javafx.graphics@18/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at javafx.graphics@18/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:184)
... 1 more

Answer 1

创建客户端类public，因为JavaFX Applicaions中的主类必须有一个公共访问修饰符，以供Application类中的getConstructor()方法选择。在正常情况下，它不会导致错误，但你的主类不会成为程序的入口点(在JavaFx Applicaions中，入口点是Applicaion类)。

你可以在这里进一步阅读