Question

Hi! I'm working on building a GUI that makes cars race across the screen. So far my code produces three cars, and they each show up without error, but do not move across the screen. Can someone point me in the right direction? Thank you!

CarComponent.java

package p5;

import java.awt.*;

import java.util.*;

import javax.swing.*;

@SuppressWarnings("serial")

public class CarComponent extends JComponent {

private ArrayList<Car> cars;

public CarComponent()

{

cars = new ArrayList<Car>();

}

public void add(Car car)

{

cars.add(car);

}

public void moveCars(int x, int y)

{

/*Controls the cars movement and the car direction.  

* Move the cars 1 pixal at time to start.

* Later move them a random distance, so they race.

*/

int len = cars.size();

for(int i = 0; i < len; i++)

{

cars.get(i).translate(50, 0);

repaint();

}

}

public void paintComponent (Graphics g)

{

Graphics2D g2 = (Graphics2D) g;

Car car1 = new Car(0,5);

//int x = ;

//int y = ;

Car car2 = new Car(0,40);

Car car3 = new Car(0,80);

//int x = ;

//int y = ;

car1.draw(g2);

car2.draw(g2);

car3.draw(g2);

}

}

Car.java

package p5;

import java.awt.*;

import java.awt.geom.Ellipse2D;

import java.awt.geom.Line2D;

import java.awt.geom.Point2D;

@SuppressWarnings("serial")

public class Car {

private int xLeft;

private int yTop;

private boolean forward;

public Car(int x, int y)

{

xLeft = x;

yTop = y;

forward = true;

}

public void translate(int dx, int dy)

{

if (xLeft == 240)

{

forward = false;

}

if(forward)

{

xLeft += dx;

yTop += dy;

}

}

public void draw(Graphics2D g2)

{

Rectangle body = new Rectangle(xLeft, yTop +10, 60, 10);

Ellipse2D.Double frontTire = new Ellipse2D.Double(xLeft + 10, yTop + 20, 10, 10);

Ellipse2D.Double rearTire = new Ellipse2D.Double(xLeft + 40, yTop +20, 10, 10);

//Bottom of front windshield.

Point2D.Double r1 = new Point2D.Double(xLeft + 10, yTop + 10);

//Front of the roof.

Point2D.Double r2 = new Point2D.Double(xLeft + 20, yTop);

//Rear of the roof.

Point2D.Double r3 = new Point2D.Double(xLeft + 40, yTop);

//Bottom of the rear windshield.

Point2D.Double r4 = new Point2D.Double(xLeft + 50, yTop + 10);

Line2D.Double frontWindshield = new Line2D.Double(r1, r2);

Line2D.Double roofTop = new Line2D.Double(r2, r3);

Line2D.Double rearWindshield = new Line2D.Double(r3, r4);

g2.draw(body);

g2.draw(frontTire);

g2.draw(rearTire);

g2.draw(frontWindshield);

g2.draw(roofTop);

g2.draw(rearWindshield);

}

public int getXLeft(int xLeft)

{

return xLeft;

}

public int getYTop(int yTop)

{

return yTop;

}

public boolean getForward(boolean forward)

{

return forward;

}

public void setForward(boolean forward)

{

forward = true;

}

}

CarMover.java

package p5;

import java.awt.*;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.util.Scanner;

import java.util.*;

import javax.swing.Timer;

import javax.swing.JFrame;

import java.awt.event.ActionEvent;

@SuppressWarnings("serial")

public class CarMover {

private static final int FRAME_WIDTH = 300;

private static final int FRAME_HEIGHT = 400;

public static void main(String[] args)

{

JFrame frame = new JFrame();

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

CarComponent component = new CarComponent();

component.add(new Car(0, 10));

component.add(new Car(0, 50));

component.add(new Car(0, 100));

frame.add(component);

frame.setSize(FRAME_WIDTH, FRAME_HEIGHT);

frame.setVisible(true);

System.out.println("Set the x value for the movement of the car: ");

Scanner keyboard = new Scanner(System.in);

int movement = keyboard.nextInt();

class TimerListener implements ActionListener

{

public void actionPerformed(ActionEvent event)

{

component.moveCars(50, 0);

}

}

ActionListener listener = new TimerListener();

final int DELAY = 50; // Milliseconds between timer ticks

Timer t = new Timer(DELAY, listener);

t.start();

}

}

Answer 1

• I really understand your concern and debug your rewrite your code in fresh manner so that it produce desirable output.
• It contain the output of three moving car.

Source code:-

CarsMover

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.Timer;

public class CarsMover {

    private static final int FRAME_WIDTH = 300;
    private static final int FRAME_HEIGHT = 400;
    private static final int CAR_HEIGHT = 40;
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        JFrame frame = new JFrame();

        frame.setSize(FRAME_WIDTH, FRAME_HEIGHT);
        frame.setLayout(new GridLayout(3,1));
        frame.setTitle("CarMover");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        final CarComponent component = new CarComponent();
        component.setPreferredSize(new Dimension(FRAME_WIDTH, CAR_HEIGHT));
      
        final CarComponent blueCar = new CarComponent(FRAME_WIDTH-80, 0, Color.BLUE);
        component.setPreferredSize(new Dimension(FRAME_WIDTH, CAR_HEIGHT));
      
      
        final CarComponent redCar = new CarComponent(0,0, Color.RED);
        component.setPreferredSize(new Dimension(FRAME_WIDTH, CAR_HEIGHT));
      
        frame.add(component);
        frame.add(blueCar);
        frame.add(redCar);
        frame.setVisible(true);

        class TimerListener implements ActionListener {

            public void actionPerformed(ActionEvent event) {
                component.moveCarBy(5, 0);
                component.repaint();
                blueCar.moveCarBy(-5,0);
                blueCar.repaint();
                redCar.moveCarBy(5,0);
                redCar.repaint();
            }
        }
        ActionListener listener = new TimerListener();

        final int DELAY = 100; // Milliseconds between timer ticks
        Timer t = new Timer(DELAY, listener);
        t.start();
    }

}

---------------------------------------------------------------------------------------------------------------

CarComponent

import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JComponent;

/**
* This component displays a car that can be moved.
*/
public class CarComponent extends JComponent {

    private Car car;
    private Color bodyColor;
  
    public CarComponent() {
        // The rectangle that the paint method draws
        car = new Car(0, 0);
    }
  
    public CarComponent(int x, int y, Color _bodyColor)
    {
        bodyColor = _bodyColor;
        car = new Car(x, y);
    }
  
    public void paintComponent(Graphics g) {
        g.setColor(bodyColor);
        car.draw(g);
    }

    /**
     * Moves the rectangle by a given amount.
     *
     * @param x the amount to move in the x-direction
     * @param y the amount to move in the y-direction
     */
    public void moveCarBy(int dx, int dy) {
        car.translate(dx, dy);
        repaint();
    }

}

------------------------------------------------------------------------------------------

Car

import java.awt.Graphics;
import javax.swing.JComponent;

/**
* A car shape that can be positioned anywhere on the screen.
*/
public class Car {

    private int xLeft;
    private int yTop;

    /**
     * Constructs a car with a given top left corner
     *
     * @param x the x coordinate of the top left corner
     * @param y the y coordinate of the top left corner
     */
    public Car(int x, int y) {
        xLeft = x;
        yTop = y;
    }

    /**
     * Moves this car by a given distance.
     *
     * @param dx the distance in x-direction
     * @param dy the distance in y-direction
     */
    public void translate(int dx, int dy) {
        xLeft = xLeft + dx;
        yTop = yTop + dy;
    }

    /**
     * Draws the car.
     *
     * @param g the graphics context
     */
    public void draw(Graphics g) {
        g.drawRect(xLeft, yTop + 10, 60, 10);
        g.drawOval(xLeft + 10, yTop + 20, 10, 10);
        g.drawOval(xLeft + 40, yTop + 20, 10, 10);

        g.drawLine(xLeft + 10, yTop + 10, xLeft + 20, yTop);
        g.drawLine(xLeft + 20, yTop, xLeft + 40, yTop);
        g.drawLine(xLeft + 40, yTop, xLeft + 50, yTop + 10);
    }
}

---------------------------------------------------------------------------------------------

Output:-

******************************************************************************************

if you are satisfy with my answer then please,please like it.