How to not let my image move out of scene

Question

Here is my following code:

    public void start(Stage primaryStage) throws Exception {
    Pane root = new Pane();
    Scene scene = new Scene(root, 500, 500, Color.RED);

    ImageView dice = new ImageView(new Image(getClass().getResourceAsStream("dice.jpeg")));
    dice.setX(0);
    dice.setY(300);
    root.getChildren().add(dice);

    scene.setOnKeyPressed(e -> {
        if (dice.getX() >= 0 &&  dice.getX() <= 500 ) {
            switch (e.getCode()) {

                case RIGHT:
                    dice.setX(dice.getX() + KEYBOARD_MOVEMENT_DELTA);
                    break;

                case LEFT:
                    dice.setX(dice.getX() - KEYBOARD_MOVEMENT_DELTA);
                    break;
             }
           }
    });

    primaryStage.setScene(scene);
    primaryStage.show();
}

In my code, my image dice can move left and right, but I don't want it to go outside the scene. I want it to not move once it reaches to end of the scene in both left and right. I tried doing it with if statement, but it doesn't work. Is there any way I can stop my image diceto not move out of scene? Any help is appreciated!

Answer 1

You have a couple of problems in your answer. Firstly, the way you check the boundaries. If the condition is met, your keys no longer control the ImageView. Secondly, using dice.getX() in your test condition. It's best if you use dice.getLayoutBounds().getMaxX() and dice.getLayoutBounds().getMinX(). Also, I recommend using scene.getWidth() instead of hard coding the width of the Scene, because the Scene width can be changed. <-(in your posted code).

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

/**
 *
 * @author blj0011
 */
public class JavaFxTestingGround extends Application {

    double KEYBOARD_MOVEMENT_DELTA = 5;

    @Override
    public void start(Stage primaryStage) throws IOException {
        Pane root = new Pane();
        Scene scene = new Scene(root, 500, 500, Color.RED);

        ImageView dice = new ImageView(createImage("https://cdn.discordapp.com/attachments/250163910454280192/296377451599364107/Untitled.png"));
        dice.setFitHeight(100);
        dice.setFitWidth(100);
        dice.setX(0);
        dice.setY(300);
        root.getChildren().add(dice);

        scene.setOnKeyPressed(e -> {       
            System.out.println(dice.getLayoutBounds().getMinX() + " : " + dice.getLayoutBounds().getMaxX() + " : " + scene.getWidth());
            switch (e.getCode()) {
                case RIGHT:
                    dice.setX(dice.getX() + KEYBOARD_MOVEMENT_DELTA);
                    break;

                case LEFT:
                    dice.setX(dice.getX() - KEYBOARD_MOVEMENT_DELTA);
                    break;
             }


            if (dice.getLayoutBounds().getMinX() < 0)   
            {
                dice.setX(0);
            }            
            else if(dice.getLayoutBounds().getMaxX() > scene.getWidth() )
            {
                dice.setX(dice.getX() - KEYBOARD_MOVEMENT_DELTA);
            }           
        });

        primaryStage.setScene(scene);
        primaryStage.show();
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }

    Image createImage(String url)
    throws IOException {
        URLConnection conn = new URL(url).openConnection();
        conn.setRequestProperty("User-Agent", "Wget/1.13.4 (linux-gnu)");

        try (InputStream stream = conn.getInputStream()) {
            return new Image(stream);
        }
    }
}