How to update Graphics in java?

Question

I will preface this by saying I do not have any prior experience with java graphics etc. so the code may be quite wrong...pretty new to java also so please try and keep things simple when explaining them :P

ok so I have looked in the API and found a repaint method but I am not entirely sure how to use it. My code at the moment is:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;

/* Class extending Jframe */
public class Train extends JFrame {
    String onOffValue = "OFF";
    String dOpenValue = "CLOSED";
    String tMovingValue = "NO";
    String tReadyValue = "NO";
    String trainInfoContent = "AH HERROOOO!!";
    int stationNo = 0;

    /* Constuctor method for the object */
    Train() {
        /* setting the frame title */
        super("Train Control System");
        /* calling buildGUI to set up the interface */
        buildGUI();

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
        setVisible(true);
    }

    private void buildGUI() {
        JPanel station = new JPanel();
            station.setLayout(new BorderLayout());
            JPanel Graphic = new JPanel();
                Graphic g = new Graphic(stationNo);
                Graphic.add(g);
            station.add(Graphic, BorderLayout.NORTH);
            station.setBorder(new TitledBorder(new EtchedBorder(), " Station     Information "));
        add(station, BorderLayout.NORTH);

        JPanel trains = new JPanel();
            trains.setLayout(new BorderLayout());
            JTextArea trainInfo = new JTextArea(trainInfoContent, 3, 70);
            trains.add(trainInfo);
            trains.setBorder(new TitledBorder(new EtchedBorder(), " Train Information "));
        add(trains, BorderLayout.CENTER);

        JPanel controls = new JPanel();

            controls.setLayout(new BorderLayout());
            JPanel buttons = new JPanel();
                buttons.setLayout(new GridLayout(3, 2));
                buttons.setBorder(BorderFactory.createEmptyBorder(10,10,10,10));
                Button start = new Button("Start Train");
                buttons.add(start);
                update test = new update(trainInfo, stationNo, Graphic);
                start.addActionListener(test); 
                Button open = new Button("Open Doors");
                buttons.add(open);
                Button close = new Button("Close Doors");
                buttons.add(close);
                Button go = new Button("Go");
                buttons.add(go);
                Button stop = new Button("Stop");
                buttons.add(stop);
                Button shutdown = new Button("Shutdown Train");
                buttons.add(shutdown);
            controls.add(buttons, BorderLayout.WEST);

            JPanel display = new JPanel();
                display.setLayout(new GridLayout(2, 4));

                JTextField onOffTitle = new JTextField("Train on: ");
                onOffTitle.setEditable(false);
                display.add(onOffTitle);
                JTextField onOff = new JTextField(onOffValue);
                onOff.setEditable(false);
                display.add(onOff);

                JTextField dOpenTitle = new JTextField("Doors Open: ");
                dOpenTitle.setEditable(false);
                display.add(dOpenTitle);
                JTextField dOpen = new JTextField(dOpenValue);
                dOpen.setEditable(false);
                display.add(dOpen);

                JTextField tMovingTitle = new JTextField("Train Moving: ");
                tMovingTitle.setEditable(false);
                display.add(tMovingTitle);
                JTextField tMoving = new JTextField(tMovingValue);
                tMoving.setEditable(false);
                display.add(tMoving);

                JTextField tReadyTitle = new JTextField("Train Ready: ");
                tReadyTitle.setEditable(false);
                display.add(tReadyTitle);
                JTextField tReady = new JTextField(tReadyValue);
                tReady.setEditable(false);
                display.add(tReady);

            controls.add(display, BorderLayout.CENTER);
        add(controls, BorderLayout.SOUTH);
    }
    /* Main method declaring a new train control system object */
    public static void main(String[] args) {
        Train TCS = new Train();
    }
}    

class Graphic extends JPanel {

    int station;

    Graphic(int s) {
        station = s;
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;

        g2.drawString("Darlington", 1, 36);
        g2.drawString("North Road", 140, 36);
        g2.drawString("Heighington", 280, 36);
        g2.drawString("Shildon", 436, 36);
        g2.drawString("Newton Aycliffe", 560, 36);
        g2.drawString("Bishop Auckland", 698, 36);

        g2.setStroke(new BasicStroke(5));
        g2.drawLine(25, 11, 742, 11);
        g2.setColor(Color.gray);
        g2.drawLine(25, 11, 25+(station*143), 11);

        g2.setStroke(new BasicStroke(9));
        int x = 23;
        for (int i = 0; i < 6; i++) {
            g2.drawOval(x, 7, 10, 10);
            x = x + 143;
        }
        g2.setColor(Color.black);
        x = 23 + (station*143);
        for (int i = 0; i < 6; i++) {
            g2.drawOval(x, 7, 10, 10);
            x = x + 143;
        }

        g2.setColor(Color.white);
        x = 23;
        for (int i = 0; i < 6; i++) {
            g2.fillOval(x, 7, 10, 10);
            x = x + 143;
        }
        g2.setColor(Color.red);
        g2.fillOval(23 + (143*station), 7, 10, 10);
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(800, 40);
    }
}    

class update implements ActionListener {
    JTextArea output;
    int stationNo;
    JPanel graphic;

    update(JTextArea out, int station, JPanel p) {
        output = out;
        stationNo = station;
        graphic = p;
    }

    public void actionPerformed(ActionEvent e)   {
        output.append("Start Train");
        stationNo = stationNo + 1;
        graphic.repaint();
        output.append(" " + stationNo);
    }    
}

I'm sorry if there's a lot of code I wasn't sure which parts people would need to help :/

I can see why my code at the moment isn't working but it's the closest I can get to it working...

Forgot to say thanks in advance! :) (where are my manners)

Answer 1

So I managed to get my code working.

The problem was I needed a method in my Graphic class to update the object's StationNo and that in the update class I should have been accepting a Graphic object rather than a JPanel.

the changes I made are:

class update implements ActionListener {
    JTextArea output;
    int stationNo;
    Graphic graphic;

    update(JTextArea out, int station, Graphic p) {
        output = out;
        stationNo = station;
        graphic = p;
    }

    public void actionPerformed(ActionEvent e)   {
        output.append("Start Train");
        stationNo = stationNo + 1;
        graphic.newStation(stationNo);
        graphic.repaint();
        output.append(" " + stationNo);
    }
}

and the newStation method is just

public void newStation(int s) {
    stationNo = s;
}

So just me being silly methinks...

Answer 2

Please study about Java coding formats first.Then start coding the APP. Each and every variable in java must want to start with a small letter. Only class will start with a Capital letter. Just change this.

JPanel Graphic = new JPanel();
                Graphic g = new Graphic(stationNo);
                Graphic.add(g);
            station.add(Graphic, BorderLayout.NORTH);

TO

   JPanel graphic = new JPanel();
            Graphic g = new Graphic(stationNo);
            graphic.add(g);
        station.add(graphic, BorderLayout.NORTH);

Then you can use repaint() method in a while loop. When the repaint() method is called the paintComponent(Graphics g) method will be fired and the code in it will be executed.