JavaFX: Preloader stop after start before show of the Application

Question

Given an JavaFX Application

public class App extends Application{
 @Override
    public void init() throws Exception {
        // Do some huge task 
     }
    @Override
    public void start(Stage primaryStage) {
    // even a bigger task 
    }
}

and a Preloader class

public class PreloadScreen extends Preloader {
// all the overwritten methods 
@Override
    public void handleStateChangeNotification(StateChangeNotification info) {
        // Handle state change notifications.
        StateChangeNotification.Type type = info.getType();
      if(type.equals(BEFORE_START))
     // hide the preloader 
    }
}

As I understand correctly the Preloader hides before the start() of the application. Consider this image as visualisation Is it possible to add StateChangeNotification into the enum like BEFORE_SHOW I have a very intensive task that needs the stage of the start method in the application.

Answer 1

Define a custom progress message:

public class ProgressMessage implements Preloader.PreloaderNotification
{
    public static final ProgressMessage SUCCESSFULLY_DONE = new ProgressMessage(true, false);
    public static final ProgressMessage FAILED = new ProgressMessage(false, true);

    // TODO: add a variable to hold the exception in case of failure.
    private double progress;
    private String message;
    private boolean done;
    private boolean failed;

    public ProgressMessage(double progress, String message)
    {
        this.progress = progress;
        this.message = message;
        this.done = false;
        this.failed = false;
    }

    private ProgressMessage(boolean done, boolean failed)
    {
        this.done = done;
        this.failed = failed;
    }

    public double getProgress(){return progress;}
    public String getMessage(){return message;}
    public boolean isDone(){return done;}
    public boolean isFailed(){return failed;}

    @Override
    public boolean equals(Object o)
    {
        if(this == o) return true;
        if(o == null || getClass() != o.getClass()) return false;
        ProgressMessage message1 = (ProgressMessage) o;
        return Double.compare(message1.progress, progress) == 0 &&
               done == message1.done && failed == message1.failed &&
               Objects.equals(message, message1.message);
    }

    @Override
    public int hashCode()
    {
        return Objects.hash(progress, message, done, failed);
    }

    @Override
    public String toString()
    {
        return "ProgressMessage{" + "progress=" + progress + ", message='" +
               message + '\'' + ", done=" + done + ", failed=" + failed + '}';
    }
}

Inside the Preloader, override handleApplicationNotification(PreloaderNotification info):

@Override
public void handleApplicationNotification(PreloaderNotification info)
{
    ProgressMessage progressMessage = (ProgressMessage) info;

    if(progressMessage.isDone())
    {
        splashScreenStage.hide();
        LOGGER.info("The splash screen is closed");
    }
    else if(progressMessage.isFailed())
    {
        // TODO: receive the exception from the main application.
        // TODO: show error dialog here with exception details.
        LOGGER.error("Exiting the application due to an error during the startup!");
        splashScreenStage.hide();
        Platform.exit();
    }
    else
    {
        double progress = progressMessage.getProgress();
        String message = progressMessage.getMessage();

        LOGGER.info("New Progress: progress({}), message({})", progress, message);

        splashScreenController.setProgress(progress);
        splashScreenController.setProgressMessage(message);
    }
}

Now, from your main application you can invoke the following methods to notify the progress:

notifyPreloader(new ProgressMessage(0.5, "Downloading some data from the backend server")); // 0.5 = 50%
notifyPreloader(ProgressMessage.SUCCESSFULLY_DONE);
notifyPreloader(ProgressMessage.FAILED);