从 IntelliJ 运行 JavaFX 应用程序

Question

Versions

openjdk version "11.0.11" 2021-04-20

OpenJDK Runtime Environment (build 11.0.11+9-Ubuntu-0ubuntu2.20.10)

OpenJDK 64-Bit Server VM (build 11.0.11+9-Ubuntu-0ubuntu2.20.10, mixed mode, sharing)

IntelliJ IDEA 2021.1.2 (Ultimate Edition) Build #IU-211.7442.40, built on May 31, 2021

JavaFX SDK 11.0.2

Hey guys, first I want to say that this question was somewhat asked before here I followed all the steps that the correct answer gives, and end up with this error:

Exception in Application start method 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 javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:464)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:363)
    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 java.base/sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:1071)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:900)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication$2(LauncherImpl.java:195)
    at java.base/java.lang.Thread.run(Thread.java:831)
Caused by: java.lang.IllegalAccessError: class com.sun.javafx.fxml.FXMLLoaderHelper (in unnamed module @0x6c5aff76) cannot access class com.sun.javafx.util.Utils (in module javafx.graphics) because module javafx.graphics does not export com.sun.javafx.util to unnamed module @0x6c5aff76
    at com.sun.javafx.fxml.FXMLLoaderHelper.<clinit>(FXMLLoaderHelper.java:38)
    at javafx.fxml.FXMLLoader.<clinit>(FXMLLoader.java:2056)
    at KiloConverter.start(KiloConverter.java:12)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:846)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:455)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:428)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:427)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at javafx.graphics/com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.gtk.GtkApplication.lambda$runLoop$11(GtkApplication.java:277)

I am somewhat of a beginner with Java, and I am doing this project for a college course. I can build the application, but cannot run it. Like I said, I followed all the steps the previous answer gave, to no avail.

Please if possible, don't tell me to "read up on the basics" like I saw other people answer before . I just am not sure why my code won't run for my final project.

Thank you so much in advance!

Answer 1

Since you mention you're a beginner in Java I first recommend reading this Q&A: What is a stack trace, and how can I use it to debug my application errors? . Then when you look back at your stack trace you'll see the fundamental error you're getting is:

Caused by: java.lang.IllegalAccessError: class com.sun.javafx.fxml.FXMLLoaderHelper (in unnamed module @0x6c5aff76) cannot access class com.sun.javafx.util.Utils (in module javafx.graphics) because module javafx.graphics does not export com.sun.javafx.util to unnamed module @0x6c5aff76

This is a module-related error. You may want to read Understanding Java 9 Modules to familiarize yourself with modules.

In this case the error occurs because the javafx.fxml module is being found on the class-path while the javafx.graphics module is being found on the module-path. In other words, the javafx.fxml module is failing to be resolved as a named module but its code is still being found in the unnamed module . This breaks the qualified exports and qualified opens directives that javafx.graphics may give to javafx.fxml and the result is the IllegalAccessError .

You need to make sure the javafx.fxml module is actually resolved as a module. There are at least two ways to do this:

1. Include javafx.fxml in your --add-modules JVM argument.

2. Make your code modular by adding a module-info.java file:

    // or whatever you want to name your module module app { requires javafx.controls; requires javafx.fxml; // export your Application subclass's package to at least javafx.graphics exports com.example.app to javafx.graphics; // open your FXML controller package(s) to at least javafx.fxml (allows reflective access) opens com.example.app.controllers to javafx.fxml; }

   And launch your application as a module. For example, this is what it would look like on the command line:

    java --module-path <path> --module <module>/<main-class>