java eclipse error: javafx runtime components are missing, and are required to run this application

I have this classical issue: Using JavaFX 11 with OpenJDK 11 together with Eclipse IDE.

Error: JavaFX runtime components are missing, and are required to run this application

I have OpenJDK 11.0.2

dell@dell-pc:~$ java -version
openjdk version "11.0.2" 2019-01-15
OpenJDK Runtime Environment 18.9 (build 11.0.2+9)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.2+9, mixed mode)
dell@dell-pc:~$ 

Answer:

Your problem is not compiling the project, but running it. Since your main is defined in your Application-extension, running the project will require JavaFX in your module path on startup.

So either outsource your main into a class different from your Application or add the JavaFX modules with VM arguments:

--module-path="<javafx-root>\lib" --add-modules="javafx.base,javafx.controls,..."

See this for some more info.