Notification when the stage is vissible on the screen

Question

Hi all,
I'm creating a JavaFx application which is a client application that interacts with an server. I created a preloader like scene which shows the progress (with a progress bar) when the application receives a broadcast from the server with server location, application initialization and when started for the first time the user must give a client name. I do not use the preloader interface because it seems to be discarded on the raspberry pi (correct me if i'm wrong, but i'm using a log file and nothing is written to the file from the preloader i created before this attempt).
This all works fine, user can do input, and when te client starts for the second time and later, the client automaticaly logs in. When i start this client on my development machine i see the preloader scene starting from the beginning. But when i start the same application on the raspberry pi (which offcourse is a LOT slower), the preloader scene is not earlier visible then when:
- The client receives the broadcast from the server after 4/5 seconds, because the application is then in a "wait" state.
- Or when the broadcast is recieved quite fast, when there is user input needed,
- When the broadcast is recieved quite fast and there is no user input needed, i rarely see the preloader scene appearing.
I've understand that there is a main FX thread for graphical actions and there are you're own threads etc... I have the following code to start the application initialization progress when the preloader scene comes visible in my application start method:
    public void start(Stage primaryStage) {
        redirectOutputToLog();
        rootStage = primaryStage;
        rootStage.setTitle("PiDome Client");
        rootStage.setFullScreen(true);
        rootStage.initStyle(StageStyle.UNDECORATED);
        rootStage.addEventHandler(WindowEvent.WINDOW_SHOWN, new EventHandler<WindowEvent>(){
            @Override
            public void handle(WindowEvent window){
                if(preloaderShown==false){
                    mainStage = new MainScene();
                    mainStage.setRoot(rootStage);
        ready.addListener(new ChangeListener<Boolean>(){
            @Override
            public void changed(
                ObservableValue<? extends Boolean> ov, Boolean t, Boolean t1) {
                    if (Boolean.TRUE.equals(t1)) {
                        rootStage.setScene(mainStage.scene());
                        ////rootStage.sizeToScene();
                        Networking.removeEventListener(me);
                        ClientData.removeClientDataConnectionListener(me);
                        ClientData.removeClientLoggedInConnectionListener(me);
                        Domotics.removeDomoticsListener(me);
        preloader = new PidomeClientPreloader(rootStage);
        rootStage.show();
        preloaderShown = true;
        initialize();
The constructor of the PidomeClientPreloader is creating the preloader scene and puts all the items on the scene as needed. When the preloader is done initializing the rootStage is shown. But as mentioned on the raspberry pi, the event WINDOW_SHOWN seems to be fired before the scene is graphical visible. I'm not using Platform.Runlater in my preloader code (only in one update function to update the progress bar from background threads).
Is there a way to have a absolute way of determining when a scene is really visible, or is this as far as i can get because the FX thread is always running behind?
Thnx in advance,
John.

Answer 1

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