JavaFX does not exist using Java 9 and Intellij Idea

Question

I am using Intellij Idea to compile a project that uses Maven dependencies and Intellij keeps telling me that my project has 50 something errors because JavaFX does not exist.

Intellij is not highlighting all the javafx dependencies in my code as errors, it is just that once I press the run and compile the program says that everything in JavaFX does not exists.

I tried to redownload the latest JDK (Java 9.0.1) and that did not fix it. I went into the Default Project Structure and Project Structure to make sure it was using the correct jdk and that did not fix the issue. All the jdks I am using seem to list the javafx packages as included in the project.

This is also only an issue for a particular project that I am working on with a friend. We may have to move over all our code into a new project, however I am not sure if that will fix anything.

Any suggestions?

Answer 1

I missed the modules in my gradle.build. Had to update

javafx {
  version = "11"
  modules = [ 'javafx.controls', 'javafx.fxml' ]
}

Answer 2

I had this problem after upgrading a JavaFX project from Java 8 to Java 9.

After checking the usual language level settings for the project and module in IntelliJ and the Maven pom, I found the problem was that the module was explicitly set to generate Java 8 bytecode in the Java Compiler preferences.

Look in Preferences -> Build, Execution, Deployment -> Compiler -> Java Compiler. Check that Project bytecode version is unset (or set correctly) and that your module is not listed in Per-module bytecode version with an incorrect value.