how to stop "JavaFX Application Thread"


Question

I have a simple console application which sometimes need to perform graphics operations, for those I'm using JavaFx framework (there are some functions that I need like the css styling for text ) I simply generate some shapes and text into an hidden scene then save those on file and that's all,

I know that to work with JavaFx I have to pass graphics operations to the JavaFx thread, but when everything is done and I have to close the application (after some hours) this JavaFx thread still remain open... and I really don't want to force exit with System.exit() because if something is blocked I may want to know/wait (ALSO I don't want to execute everything as an JavaFx application (as JavaFx components are less than 1% of my main application)

the code is very simple and googling around I've found only to use

Platform.exit();

which doesn't seems to work, I've also tried playing with Platform parameters like

Platform.setImplicitExit(false);

here is my test application which you can run :

import javafx.application.Platform;
import javafx.embed.swing.JFXPanel;
import javafx.geometry.Pos;
import javafx.scene.layout.VBox;

public class SOTestFX {
    public static void main(String[] args) {
        SOTestFX t = new SOTestFX();
        t.runFxThread();
    }

    public  void runFxThread(){
        //Application.launch(args);
        final JFXPanel jfxPanel = new JFXPanel(); 
        Platform.runLater(new Runnable() {
            @Override
            public void run() {

                System.err.println("CREATING IMAGE");
                simpleFXoperations();
                System.err.println("NOW CALL EXIT");
                System.err.println("JAVA FX THREAD SHOULD BE EXITED NOW");
                Platform.exit();
            }
        });

        try {
            Thread.sleep(3000); // just wait a bit if something should happen, let it happen..
        } catch (InterruptedException e) {
            e.printStackTrace();  
        }
        //jfxPanel.removeNotify(); // return ->  java.lang.NullPointerException
        //Platform.exit(); // -> does nothing

        System.err.println("i will never die!");
    }
    public void simpleFXoperations(){

        VBox vbox1 = new VBox();
        vbox1.setAlignment(Pos.BOTTOM_CENTER);
        vbox1.setStyle("-fx-border-style: solid;"
                + "-fx-border-width: 1;"
                + "-fx-border-color: white");
        System.err.println("simpleFXoperations() _DONE");
    }
}

and this is the thread which never close

"Attach Listener" - Thread t@17 java.lang.Thread.State: RUNNABLE

Locked ownable synchronizers: - None

"JavaFX Application Thread" - Thread t@13 java.lang.Thread.State: RUNNABLE at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method) at com.sun.glass.ui.gtk.GtkApplication$3$1.run(GtkApplication.java:82) at java.lang.Thread.run(Thread.java:722)

Locked ownable synchronizers: - None

Update: I'm using latest Oracle JDK 7u17 64bit on Linux Fedora 16 64bit.

1
17
4/5/2013 10:19:35 PM

Fix:

I was able to fix this problem by calling com.sun.javafx.application.PlatformImpl.tkExit() immediately before Platform.exit(). I don't really understand the JavaFX source that well, but it seems to be working; YMMV.

Update: Doing this in Java 8 will produce a warning, you can just turn the warning off with @SuppressWarnings("restriction"). It shouldn't be a problem.

Explanation:

I figured this out by digging through the source code; JFXPanel has this little snippet (this is from JavaFX 2.2.25)

finishListener = new PlatformImpl.FinishListener() {
  public void idle(boolean paramAnonymousBoolean) {
    if (!JFXPanel.firstPanelShown) {
      return;
    }
    PlatformImpl.removeListener(JFXPanel.finishListener);
    JFXPanel.access$102(null);
    if (paramAnonymousBoolean)
      Platform.exit();
  }

  public void exitCalled()
  {
  }

The problem is, if you are using only a little bit of JavaFX in your application, then the idle(boolean) method never does anything (because firstPanelShown == false), which prevents the listener from getting removed, which prevents the JavaFX Toolkit from shutting down... which means you have to shut it down manually.

25
9/17/2015 8:16:34 PM

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