Question

Java:

Exercise 15.9 Follow the instructions in the textbook, also shown here: 15.9 (Draw lines using the arrow keys) Write a program that draws line segments using the arrow keys. The line starts from the point (100,100) in the pane and draws toward cast, north, west, or south when the right-arrow key up-arrow key, left- arrow key, or down-arrow key is pressed, as shown in Figure 15.26b. Exercise15 09 JOlX (b) Figure 15.26 (b) Exercise 15.9 uses the arrow keys to draw the lines.

Answer 1

Here is the completed code for this problem. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. Thanks

// Exercise15_09.java

import javafx.application.Application;

import static javafx.application.Application.launch;

import javafx.scene.Scene;

import javafx.scene.canvas.Canvas;

import javafx.scene.canvas.GraphicsContext;

import javafx.scene.input.KeyCode;

import javafx.scene.layout.Pane;

import javafx.scene.paint.Color;

import javafx.stage.Stage;

public class Exercise15_09 extends Application {

    //starting position

    private double x = 100, y = 100;

    //represents the length of line created for a single arrow key press

    //you can modify this as you like

    private double displacement = 10;

    @Override

    public void start(Stage primaryStage) {

        //creating a Pane

        Pane root = new Pane();

        //creating a Canvas

        Canvas canvas = new Canvas(600, 600);

        //getting a GraphicsContext from canvas

        GraphicsContext gc = canvas.getGraphicsContext2D();

        //positioning gc to (x,y)

        gc.moveTo(x, y);

        //using black fill color

        gc.setFill(Color.BLACK);

        //using 5 for line thickness

        gc.setLineWidth(5);

        //adding canvas to root

        root.getChildren().add(canvas);

        //creating a Scene

        Scene scene = new Scene(root);

        //adding key pressed listener

        scene.setOnKeyPressed(e -> {

            //getting clicked key code

            KeyCode c = e.getCode();

            //finding clicked key

            if (c == KeyCode.UP) {

                //moving up

                gc.lineTo(x, y - displacement);

                //updating coordinates

                y = y - displacement;

            } else if (c == KeyCode.DOWN) {

                //moving down

                gc.lineTo(x, y + displacement);

                y = y + displacement;

            } else if (c == KeyCode.LEFT) {

                //moving left

                gc.lineTo(x - displacement, y);

                x = x - displacement;

            } else if (c == KeyCode.RIGHT) {

                //moving right

                gc.lineTo(x + displacement, y);

                x = x + displacement;

            }

            //stroking, to show the drawing

            gc.stroke();

        });

        //setting up scene and displaying

        primaryStage.setScene(scene);

        primaryStage.setTitle("Exercise15_09");

        primaryStage.show();

    }

    public static void main(String[] args) {

        launch(args);

    }

}

/*OUTPUT*/

Exercise15_09 X