Exercise15_16.java

package ch_15;

import javafx.application.Application;
import javafx.geometry.Point2D;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.shape.Line;
import javafx.scene.text.Text;
import javafx.stage.Stage;

/**
 * *15.16 (Two movable vertices and their distances) Write a program that displays two
 * circles with radius 10 at location (40, 40) and (120, 150) with a line connecting the two circles,
 * as shown in Figure 15.28b. The distance between the circles
 * is displayed along the line. The user can drag a circle. When that happens, the
 * circle and its line are moved and the distance between the circles is updated
 */
public class Exercise15_16 extends Application {

    @Override
    public void start(Stage primaryStage) {
        Pane pane = new Pane();
        Circle circle1 = new Circle(40, 40, 10);
        circle1.setFill(Color.WHITE);
        circle1.setStroke(Color.BLACK);
        Circle circle2 = new Circle(120, 150, 10);
        circle2.setFill(Color.WHITE);
        circle2.setStroke(Color.BLACK);
        Line line = new Line(circle1.getCenterX(), circle1.getCenterY(),
                circle2.getCenterX(), circle2.getCenterY());

        double distance = new Point2D(circle1.getCenterX(),
                circle1.getCenterY()).distance(circle2.getCenterX(), circle2.getCenterY());
        Text text = new Text((circle1.getCenterX() + circle2.getCenterX()) / 2,
                (circle1.getCenterY() + circle2.getCenterY()) / 2, (int) distance + "");
        pane.getChildren().addAll(line, circle1, circle2, text);

        circle1.setOnMouseDragged(e -> {
            circle1.setCenterX(e.getX());
            circle1.setCenterY(e.getY());
            line.setStartX(e.getX());
            line.setStartY(e.getY());
            double d = new Point2D(circle1.getCenterX(), circle1.getCenterY()).distance(circle2.getCenterX(), circle2.getCenterY());
            text.setX((circle1.getCenterX() + circle2.getCenterX()) / 2);
            text.setY((circle1.getCenterY() + circle2.getCenterY()) / 2);
            text.setText(d + "");
        });

        circle2.setOnMouseDragged(e -> {
            circle2.setCenterX(e.getX());
            circle2.setCenterY(e.getY());
            line.setEndX(e.getX());
            line.setEndY(e.getY());
            double d = new Point2D(circle1.getCenterX(), circle1.getCenterY()).distance(circle2.getCenterX(), circle2.getCenterY());
            text.setX((circle1.getCenterX() + circle2.getCenterX()) / 2);
            text.setY((circle1.getCenterY() + circle2.getCenterY()) / 2);
            text.setText((int) d + "");
        });

        Scene scene = new Scene(pane, 400, 250);
        primaryStage.setTitle("Exercise15_16");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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