How to use FXCanvas with SWT Java 8

Question

I am trying to integrate JavaFX inside of an SWT application using FXCanvas. For reference, I am following this oracle guide

Within my IDE this chunk of code displays an error

/* Create an FXCanvas */
final FXCanvas fxCanvas = new FXCanvas(shell, SWT.NONE) {

    @Override
    public Point computeSize(int wHint, int hHint, boolean changed) {
        getScene().getWindow().sizeToScene();
        int width = (int) getScene().getWidth();
        int height = (int) getScene().getHeight();
        return new Point(width, height);
    }
};

Error:

(yes, I have imported the correct Point class: org.eclipse.swt.graphics.Point):

'computeSize(int, int, boolean)' in 'Anonymous class derived from javafx.embed.swt.FXCanvas' clashes with 'computeSize(int, int, boolean)' in 'javafx.embed.swt.FXCanvas'; attempting to use incompatible return type

However, I don't think this is the root cause... Because when I try to build the project (maven) I get this error:

package javafx.embed.swt does not exist. Which I believe is the true issue.

So after doing some research I have checked a few things, firstly, the jfxswt jar looks like it should be accessible:

and if I open the JAR, you can see FXCanvas is there:

I even tried adding the JAR manually as a library to my module, still doesn't work.

Here is my pom.xml, (i've intentionally anonymized certain info)

I will also mention that I have tried this in a fresh project without any maven dependencies, and just adding swt and such as libraries manually with the same error.

<?xml version="1.0" encoding="UTF-8"?>
<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId></groupId>
        <artifactId></artifactId>
        <version></version>
    </parent>

    <artifactId></artifactId>
    <version>2.0.0.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name></name>
    <description></description>

    <dependencies>
        <dependency>
            <groupId>pentaho-kettle</groupId>
            <artifactId>kettle-engine</artifactId>
        </dependency>
        <dependency>
            <groupId>pentaho-kettle</groupId>
            <artifactId>kettle-core</artifactId>
        </dependency>
        <dependency>
            <groupId>pentaho-kettle</groupId>
            <artifactId>kettle-ui-swt</artifactId>
        </dependency>
        <dependency>
            <groupId>org.eclipse.swt</groupId>
            <artifactId>org.eclipse.swt.gtk.linux.x86_64</artifactId>
        </dependency>
        <dependency>
            <groupId>org.eclipse</groupId>
            <artifactId>jface</artifactId>
            <version>3.3.0-I20070606-0010</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.4</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
        </dependency>
    </dependencies>
</project>

Am I missing something, any ideas?

Minivet

Can you share your pom.xml? (I assume it is a maven project as you tagged it with that.) – Lindblad

@Lindblad added the pom and some more info to the original post. – Minivet

What java version does the pom.xml defines? Is it defined in the parent? I am looking for the maven.compiler.target and maven.compiler.source values and the maven-compiler-plugin configuration. As the classes should be included in the jdk and the same error occurs with a zero-dependency module that's my best guess. The mvn help:effective-pom should output the merged configuration. – Lindblad

@Lindblad <maven.compiler.source>1.8</maven.compiler.source> <maven.compiler.target>1.8</maven.compiler.target> Both are set to 1.8, as is my jdk – Minivet

Answer 1

You will need to add the jfxswt.jar file to your classpath for compile and for execution.

This can be done by using the system scope as that jar file is part of your JDK under the jre/lib directory.

<dependency>
    <!-- GroupId/ArtifactId/Version doesn't matter unless it clashes. -->
    <groupId>jfxswt</groupId>
    <artifactId>jfxswt</artifactId>
    <version>1.8</version>
    <scope>system</scope>
    <systemPath>${java.home}/lib/jfxswt.jar</systemPath>
</dependency>

This will instruct maven to add the jre/lib/jfxswt.jar to the classpath. This could cause an issue if someone uses different JDK what has that jar in other places but for Java 8 you should be okay.

You have to add the jfxswt.jar to your classpath when you execute your application.

In maven you can use the exec plugin:

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>exec-maven-plugin</artifactId>
    <version>3.0.0</version>
    <executions>
        <execution>
            <goals>
                <goal>java</goal>
            </goals>
        </execution>
    </executions>
    <configuration>
        <mainClass>twobuttons.TwoButtons</mainClass>
        <additionalClasspathElements>
            <!-- The run environment must configure the system jar. -->
            <element>${java.home}/lib/jfxswt.jar</element>
        </additionalClasspathElements>
    </configuration>
</plugin>

Notes:

The system scope is deprecated in maven in favor of installing files to repositories. The solution above works fine at the moment.

The content of the jfxswt.jar can be part of some SWT libraries unfortunately I am not familiar with SWT. If you can find that jar in a Maven repo than just include that instead of messing with the system scope.

The twobuttons.TwoButtons class is from the tutorial you mentioned.

Lindblad