1

I have two problems one this that, if i want to show score with the circle object:

layoutV.getChildren().addAll(virus, score);

I get the following error:

Exception in thread "JavaFX Application Thread" java.lang.IllegalArgumentException: Children: duplicate children added: parent = Pane@6661fc86[styleClass=root].

As far as I understand it is because the Task wants to show multiple scores. So should I use another scene or layout to show score?

My other problem is the hitbox of the object, right know everytime i click the score goes up. I looked up the mouse event getTarget but it does not seem like I can make it so that my object is the only target to use the mouse event on.

public class Main extends Application {

    private Stage window;
    private Pane layoutV;
    private Scene scene;
    private Circle virus;
    private int score;
    private  Label scores;
    @Override
    public void start(Stage primaryStage) {
        window = primaryStage;
        window.setTitle("Enemy TEST");
        
        this.score = 0;
        scores = new Label("Score "+ score);
        
       
        
        layoutV = new Pane();
        scene = new Scene(layoutV, 600, 600);
        
        
        window.setScene(scene);
        window.show();

        Thread th = new Thread(task);
        th.setDaemon(true);
        th.start();
        

    }

    Task task = new Task<Void>() {
        @Override
        protected Void call() throws Exception {
            while (true) {
                Platform.runLater(new Runnable() {
                    @Override
                    public void run() {
                            drawCircles();
                    }
                });

                Thread.sleep(1000);
            }
        }
    };


    public void drawCircles() {
       
        double x = (double)(Math.random() * ((550 - 50) + 1)) + 50;
        double y = (double)(Math.random() * ((550 - 50) + 1)) + 50;
        double r = (double)(Math.random() * ((30 - 10) + 1)) + 10;
     
        virus = new Circle(x, y, r, Color.VIOLET);
        layoutV.setOnMouseClicked(e -> {

            if (e.getButton() == MouseButton.PRIMARY) {
                layoutV.getChildren().remove(e.getTarget()); 

                this.score++;
                System.out.println("score: "+ this.score);
                
            }
        });
        layoutV.getChildren().addAll(virus); 
        
        scene.setRoot(layoutV);
        window.setScene(scene);

    }

    public static void main(String[] args) {
        launch(args);
    }
}
jewelsea
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Take
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  • See [edit](https://stackoverflow.com/posts/69933327/revisions) for how to format code blocks and error traces. – jewelsea Nov 11 '21 at 18:53
  • thanks, i will try that. – Take Nov 11 '21 at 19:04
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    Usually, only ask one question per question, but in this case, maybe it is OK because the code is so small that it is quite useful to pick out all of the errors in it. – jewelsea Nov 11 '21 at 19:19

1 Answers1

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You have lots of issues, not just the ones from your question:

  1. Although it will work as you coded it, I don't advise spawning a thread to draw your circles, instead see:

  2. You don't need to set the root in the scene and the scene in the window every time you draw a new circle.

  3. Nor do you need to set the mouse handler on the layout every time you draw a circle.

  4. Rather than setting a mouse handler on the layout, you are better off setting a mouse handler on the circles themselves (which you can do before you add them to the scene).

  5. score is an int, not a node you can only add nodes to the scene graph.

  6. See the documentation for the scene package:

    A node may occur at most once anywhere in the scene graph. Specifically, a node must appear no more than once in the children list of a Parent or as the clip of a Node. See the Node class for more details on these restrictions.

    How you are adding the node more than once is not clear to me, because you are probably doing it in code different than the Main class you provided.

  7. To add a circle with a score on top, use a StackPane with the score in a label, but make the label mouse transparent, so that it does not register any clicks:

    Label scoreLabel = new Label(score + "");  
scoreLabel.setMouseTransparent(true);  
StackPane balloon = new StackPane(circle, scoreLabel);
layoutV.getChildren.add(balloon);

    Add the click handler on the balloon.

  8. And additional issues I don't detail here but are solved in the demo code provided.

To fix all your errors, I would write some code like below. Perhaps you can review it and compare it with your code to help understand one way to create this game.

The example code might not be exactly the functionality you are looking for (that is not really its purpose), but it should be enough to keep you on the right track for implementing your application.

image

import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.property.*;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.*;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.text.*;
import javafx.stage.Stage;
import javafx.util.Duration;

import java.util.concurrent.ThreadLocalRandom;

public class Inoculation extends Application {
    public static final int W = 600;
    public static final int H = 600;

    private final IntegerProperty score = new SimpleIntegerProperty(0);
    private final Pane playingField = new Pane();

    @Override
    public void start(Stage stage) {
        StackPane overlay = createOverlay();

        Pane layout = new StackPane(playingField, overlay);

        stage.setScene(new Scene(layout, W, H));
        stage.show();

        Infection infection = new Infection(playingField, score);
        infection.begin();
    }

    private StackPane createOverlay() {
        Label totalScoreLabel = new Label();
        totalScoreLabel.textProperty().bind(
                Bindings.concat(
                        "Score ", score.asString()
                )
        );

        StackPane overlay = new StackPane(totalScoreLabel);
        StackPane.setAlignment(totalScoreLabel, Pos.TOP_LEFT);
        overlay.setMouseTransparent(true);

        return overlay;
    }

    public static void main(String[] args) {
        launch(args);
    }
}

class Infection {
    private static final Duration SPAWN_PERIOD = Duration.seconds(1);
    private static final int NUM_SPAWNS = 10;

    private final Timeline virusGenerator;

    public Infection(Pane playingField, IntegerProperty score) {
        virusGenerator = new Timeline(
                new KeyFrame(
                     SPAWN_PERIOD, 
                     event -> spawnVirus(
                         playingField, 
                         score
                     )
                )
        );
        virusGenerator.setCycleCount(NUM_SPAWNS);
    }

    public void begin() {
        virusGenerator.play();
    }

    private void spawnVirus(Pane playingField, IntegerProperty score) {
        Virus virus = new Virus();

        virus.setOnMouseClicked(
                event -> {
                    score.set(score.get() + virus.getVirusScore());
                    playingField.getChildren().remove(virus);
                }
        );

        playingField.getChildren().add(virus);
    }
}

class Virus extends StackPane {
    private static final int MAX_SCORE = 3;
    private static final int RADIUS_INCREMENT = 10;

    private final int virusScore = nextRandInt(MAX_SCORE) + 1;

    public Virus() {
        double r = (MAX_SCORE + 1 - virusScore) * RADIUS_INCREMENT;

        Circle circle = new Circle(
                r,
                Color.VIOLET
        );

        Text virusScoreText = new Text("" + virusScore);
        virusScoreText.setBoundsType(TextBoundsType.VISUAL);
        virusScoreText.setMouseTransparent(true);

        getChildren().setAll(
                circle,
                virusScoreText
        );

        setLayoutX(nextRandInt((int) (Inoculation.W - circle.getRadius() * 2)));
        setLayoutY(nextRandInt((int) (Inoculation.H - circle.getRadius() * 2)));

        setPickOnBounds(false);
    }

    public int getVirusScore() {
        return virusScore;
    }

    // next random int between 0 (inclusive) and bound (exclusive)
    private int nextRandInt(int bound) {
        return ThreadLocalRandom.current().nextInt(bound);
    }
}

Some additional notes on this implementation that might be useful to know:

  1. The total score is placed in an overlayPane so that it is not obscured by elements added to the playingField (which contains the virus spawns).

  2. The overlayPane is made mouseTransparent, so that it won't intercept any mouse events, and the clicks will fall through to the items in the playing field.

  3. The app currently generates viruses within a fixed field size, regardless of whether you resize the window. That is just the way it is designed and coded, you could code it otherwise if wished. It would be more work to do so.

  4. The Bindings class is used to create a string expression binding which concatenates the static string "Score " with an integer property representing the score. This allows the string representing the score to be bound to the score label text in the overlay so that it automatically updates whenever the score is changed.

  5. The virus generation uses a timeline and is based on the concepts from:

  6. The application class is kept deliberately simple to handle mostly just the core application lifecycle, and the actual functionality of the application is abstracted to an Infection class which handles the spawning of the virus and a Virus class that generates a new virus.

  7. This technique is used to center a score for each individual virus on the virus:

  8. The virus itself is laid out in a StackPane. The pane has pick on bounds set to false. To remove the virus infection, you must click on the circle which represents the virus and not just anywhere in the square for the stack pane.

  9. Because circle coordinates are in local co-ordinates and the circle is in a parent stack pane representing the virus, the circle itself does not need x and y values set, instead layout x and y values are set on the enclosing pane to allow positioning of the pane representing the entire virus.

  10. The following technique is used to generate random integers in acceptable ranges using ThreadLocalRandom:

jewelsea
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