JavaFX: can you create a stage that doesn't show on the task bar and is undecorated?

I was able to workaround this issue with the following code:

    Stage stage = new Stage();

    stage.initStyle(StageStyle.UTILITY);
    stage.setMaxHeight(0);
    stage.setMaxWidth(0);
    stage.setX(Double.MAX_VALUE);

StageStyle.UTILITY will avoid creating a taskbar icon. I set the width and height to 0 make the window small and then use stage.setX(Double.MAX_VALUE) to place it far off screen so it doesn't show up. It's a bit hokey, but it seems to work fine.

JavaFX doesn't support the feature you request

You cannot do what you are asking (not show a task bar icon for an undecorated or transparent stage) using just the core Java 8 classes.

If you wish, file a feature request for this in the JavaFX issue tracker.

You could write some native JNI code and perhaps tell Windows not to display a task bar icon for your application. I do not know how you would do this.

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Suggestion on task bar icons

I think it is fairly standard windowing toolkit behaviour to show the main application window in the task bar when the main application window is not hidden, so I suggest not trying to circumvent that standard behaviour.

Suggestion on notifications and tray icons

This isn't directly related to your question title, but is just comment on the end goal of your task - notifications for tray icons.

Most tray based applications I have seen don't have a task bar icon when the window associated with the tray icon is hidden, but do have a task bar icon when the window associated with the tray icon is displayed - so I suggest you stick with that setup.

Also, notifications are a standard part of the system tray icon infrastructure itself, so I suggest you use the standard mechanisms for system tray icon notifications, rather than using your own. This will also allow the user to configure whether the tray icon and it's notifications are shown using the standard OS tray icon and notification management UIs.

I created a sample application which uses the AWT SystemTray API to provide a System tray for a JavaFX application which uses some of the suggestions from this section. You can try it out if you like.

Full system tray support will come to JavaFX (probably with Java 9) when RT-17503 Provide system tray support is implemented.

This question is not really fresh, but I had the same problem and found no solution at first, but here is my workaround :)

The best solution I found was to set the primaryStage to style Utility and to make all childStages to Style Undecorated. Then set the opacity of the primaryStage to 0.0 so its not visible: PrimaryStage:

primaryStage.initStyle(StageStyle.UTILITY);
primaryStage.setOpacity(0);
primaryStage.show();

Childs:

this.initOwner(owner);
this.initStyle(StageStyle.UNDECORATED);

Example code

public void start(Stage primaryStage) throws IOException{
    //make primaryStage utility
    primaryStage.initStyle(StageStyle.UTILITY);
    primaryStage.setOpacity(0);

    Stage secondaryStage = new Stage();
    secondaryStage.initOwner(primaryStage);
    //make secondaryStage transparent
    secondaryStage.initStyle(StageStyle.TRANSPARENT);


    //load ui via FXMLLoader
    FXMLLoader loader = new FXMLLoader(getClass().getResource("/ui.fxml"));
    AnchorPane pane = loader.load();//example with anchor pane

    Scene scene = new Scene(pane,400,400); //example width and height
    scene.setFill(Color.TRANSPARENT); //make scene transparent as well

    secondaryStage.setScene(scene);

    primaryStage.show();
    secondaryStage.show();
}