I can't get graphics to draw on my panel/canva

Question

I can't get graphics/text to draw on my panel/canvas/window in my Java program (using swing).

I even tried breaking it up into two classes, with the paintComponent in one (extends JPanel) and other stuff in another class (extends JFrame).

I've tried a panel with a Canvas and without a Canvas (both the same results).

I can't get anything to draw in the blue area. If I remember correctly, when I tried it with no panels at all, I did see graphics. I've successfully done this program in text (no window), and even an Android app (I thought the android app was hard, but that was easy compared to this).

I realize I could use JLabel's to do the text I need, or probably an editbox/edittext (whatever the swing equivalent is), but I'm a graphics oriented person, so I would like to know how to do graphics in Java (for any future projects).

Here's my code (I've only been coding in Java for 4 days, so forgive any bad style, etc. BTW, I changed some variables to global-like and made things public trying to get it to work, so forgive that too :-) Also, I originally had separate procedures for creating buttons, menus, etc. but I later put them all in one procedure in case that was the problem, so forgive that too.)

import java.util.Random;
import java.util.Date;
import java.io.*;
import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
import java.awt.event.*;

public class cookiewin extends JPanel
{

    static int randc = 1;
    static JButton b1, b2;
    JMenuBar menubar = null;
    static JFrame win = null;
    static JPanel panel = null, drawa = null;
    static Graphics2D g2n = null;
//static Graphics g2=null;

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.setColor(Color.BLACK);
        g2.drawString("This is a test", 20, 100);
        g2.drawLine(10, 10, 290, 290);
    }

    protected static ImageIcon createImageIcon(String path) {
        java.net.URL URL = TestPaint.class.getResource(path);
        if (URL != null) {
            return (new ImageIcon(URL));
        } else {
            System.err.println("Can't open '" + path + "'\n");
            return (null);
        }
    }

    public TestPaint() {
        Graphics g3;
        Container con;
        win = new JFrame("Fortune Cookie");
        win.setSize(640, 480);
        win.setLocation(100, 100);
        win.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        win.setDefaultLookAndFeelDecorated(true);
        menubar = new JMenuBar();
        JMenu menu = new JMenu("Options");
        menubar.add(menu);
        JMenuItem menuitem = new JMenuItem("Quit");
        menuitem.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent evt) {
                System.out.println("Menuitem1\n");
                win.dispose();
            }
        });
        menu.add(menuitem);
        menu.addSeparator();
        JMenuItem menuitem2 = new JMenuItem("About");
        menuitem2.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent evt) {
                System.out.println("Menuitem2\n");
            }
        });
        menu.add(menuitem2);
        win.setJMenuBar(menubar);
        panel = new JPanel();
        panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
        Color backcol = new Color(90, 0, 0);
        panel.setBackground(backcol);
        con = win.getContentPane();
        con.add(panel, BorderLayout.EAST);
        drawa = new JPanel();
        drawa.setPreferredSize(new Dimension(462, 0));
        drawa.setBorder(BorderFactory.createLineBorder(Color.yellow, 2));
        drawa.setBackground(Color.blue);
        win.setBackground(Color.magenta);
        JPanel panel2 = new JPanel();
        panel2.setBackground(backcol);
        panel2.setPreferredSize(new Dimension(400, 80));
        panel2.setLayout(new BoxLayout(panel2, BoxLayout.Y_AXIS));
        try {
            InputStream is = new FileInputStream("deng_th_.ttf");
            Font font = Font.createFont(Font.TRUETYPE_FONT, is);
            Color textcol = new Color(255, 255, 0);
            JLabel nulltext = new JLabel("    ");
            nulltext.setFont(font.deriveFont(38f));
            panel2.add(nulltext);
            JLabel titletext = new JLabel("        Fortune Cookie:");
            titletext.setFont(font.deriveFont(24f));
            titletext.setForeground(textcol);
            panel2.add(titletext);
        } catch (IOException ex) {
            System.out.println("Font File Error:");
        } catch (FontFormatException ex) {
            System.out.println("Font Error:");
        }
        con.add(panel2, BorderLayout.NORTH);
        JPanel panel3 = new JPanel();
        panel3.setBackground(backcol);
        panel3.setPreferredSize(new Dimension(400, 10));
        con.add(panel3, BorderLayout.SOUTH);
        JPanel panel4 = new JPanel();
        panel4.setBackground(backcol);
        panel4.setPreferredSize(new Dimension(10, 400));
        con.add(panel4, BorderLayout.WEST);
        b1 = new JButton("Another");
        b1.setToolTipText("Get another fortune cookie");
        b1.setPreferredSize(new Dimension(150, 48));
        b1.setMinimumSize(new Dimension(150, 48));
        b1.setMaximumSize(new Dimension(150, 48));
        b1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent evt) {
                System.out.println("Button1\n");
            }
        });
        ImageIcon b2i = createImageIcon("rand.jpg");
        b2 = new JButton("Non-Random", b2i);
        b2.setToolTipText("Toggle random selection");
        b2.setPreferredSize(new Dimension(150, 48));
        b2.setMinimumSize(new Dimension(150, 48));
        b2.setMaximumSize(new Dimension(150, 48));
        b2.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent evt) {
                System.out.println("Button2\n");
                randc = 1 - randc;
                if (randc == 0) {
                    b2.setText("Random");
                } else {
                    b2.setText("Non-Random");
                }
            }
        });
        panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
        panel.add(b1);
        panel.add(Box.createRigidArea(new Dimension(0, 10)));
        panel.add(b2);
        Canvas can = new Canvas();
        Color cancol = new Color(220, 220, 220);
        can.setBackground(cancol);
        drawa.add(can);
        con.add(drawa, BorderLayout.CENTER);
        win.setIconImage(new ImageIcon("rand.png").getImage());
        win.setVisible(true);
    }

    public static void main(String[] args) {
        int i, numcook = 0, x, y;
        int[] cookiepos = new int[500];
        Random ranGen2 = new Random();
        long seed;
        File fp = new File("cookie.idx");

        new TestPaint();

    }

}

Answer 1

You're basically completely ignoring the component with the custom paint. You build this UI without ever adding the panel to it.

This means your paintComponent method is never called.

Take ALL the UI creation code out of the cookiewin pane and place it somewhere else and THEN add the cookiewin panel into somewhere ...

And with example

public class TestPaint {

    protected static ImageIcon createImageIcon(String path) {
        java.net.URL URL = TestPaint.class.getResource(path);
        if (URL != null) {
            return (new ImageIcon(URL));
        } else {
            System.err.println("Can't open '" + path + "'\n");
            return (null);
        }
    }
    private JFrame win;
    private JMenuBar menubar;
    private JPanel panel;
    private Container con;
    private JPanel drawa;
    private JButton b1;
    private JButton b2;

    public TestPaint() {

        win = new JFrame("Fortune Cookie");
        win.setSize(640, 480);
        win.setLocation(100, 100);
        win.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        win.setDefaultLookAndFeelDecorated(true);

        menubar = new JMenuBar();
        JMenu menu = new JMenu("Options");
        menubar.add(menu);
        JMenuItem menuitem = new JMenuItem("Quit");
        menuitem.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent evt) {
                System.out.println("Menuitem1\n");
                win.dispose();
            }
        });
        menu.add(menuitem);
        menu.addSeparator();
        JMenuItem menuitem2 = new JMenuItem("About");
        menuitem2.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent evt) {
                System.out.println("Menuitem2\n");
            }
        });
        menu.add(menuitem2);
        win.setJMenuBar(menubar);
        panel = new JPanel();
        panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
        Color backcol = new Color(90, 0, 0);
        panel.setBackground(backcol);
        con = win.getContentPane();
        con.add(panel, BorderLayout.EAST);
        drawa = new JPanel();
        drawa.setPreferredSize(new Dimension(462, 0));
        drawa.setBorder(BorderFactory.createLineBorder(Color.yellow, 2));
        drawa.setBackground(Color.blue);
        win.setBackground(Color.magenta);
        JPanel panel2 = new JPanel();
        panel2.setBackground(backcol);
        panel2.setPreferredSize(new Dimension(400, 80));
        panel2.setLayout(new BoxLayout(panel2, BoxLayout.Y_AXIS));
        try {
            InputStream is = new FileInputStream("deng_th_.ttf");
            Font font = Font.createFont(Font.TRUETYPE_FONT, is);
            Color textcol = new Color(255, 255, 0);
            JLabel nulltext = new JLabel("    ");
            nulltext.setFont(font.deriveFont(38f));
            panel2.add(nulltext);
            JLabel titletext = new JLabel("        Fortune Cookie:");
            titletext.setFont(font.deriveFont(24f));
            titletext.setForeground(textcol);
            panel2.add(titletext);
        } catch (IOException ex) {
            System.out.println("Font File Error:");
        } catch (FontFormatException ex) {
            System.out.println("Font Error:");
        }
        con.add(panel2, BorderLayout.NORTH);
        JPanel panel3 = new JPanel();
        panel3.setBackground(backcol);
        panel3.setPreferredSize(new Dimension(400, 10));
        con.add(panel3, BorderLayout.SOUTH);
        JPanel panel4 = new JPanel();
        panel4.setBackground(backcol);
        panel4.setPreferredSize(new Dimension(10, 400));
        con.add(panel4, BorderLayout.WEST);
        b1 = new JButton("Another");
        b1.setToolTipText("Get another fortune cookie");
        b1.setPreferredSize(new Dimension(150, 48));
        b1.setMinimumSize(new Dimension(150, 48));
        b1.setMaximumSize(new Dimension(150, 48));
        b1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent evt) {
                System.out.println("Button1\n");
            }
        });
        ImageIcon b2i = createImageIcon("rand.jpg");
        b2 = new JButton("Non-Random", b2i);
        b2.setToolTipText("Toggle random selection");
        b2.setPreferredSize(new Dimension(150, 48));
        b2.setMinimumSize(new Dimension(150, 48));
        b2.setMaximumSize(new Dimension(150, 48));
        b2.addActionListener(new ActionListener() {
            private int randc;
            public void actionPerformed(ActionEvent evt) {
                System.out.println("Button2\n");
                randc = 1 - randc;
                if (randc == 0) {
                    b2.setText("Random");
                } else {
                    b2.setText("Non-Random");
                }
            }
        });
        panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
        panel.add(b1);
        panel.add(Box.createRigidArea(new Dimension(0, 10)));
        panel.add(b2);
//        Canvas can = new Canvas();
        Color cancol = new Color(220, 220, 220);
//        can.setBackground(cancol);
//        drawa.add(can);
        con.add(drawa, BorderLayout.CENTER);
        con.add(new CustomPaint(), BorderLayout.NORTH);
        win.setIconImage(new ImageIcon("rand.png").getImage());
        win.setVisible(true);
    }

    public static void main(String[] args) {
        int i, numcook = 0, x, y;
        int[] cookiepos = new int[500];
        Random ranGen2 = new Random();
        long seed;
        File fp = new File("cookie.idx");

        new TestPaint();

    }

    public class CustomPaint extends JPanel {

        @Override
        public Dimension getPreferredSize() {

            return new Dimension(100, 100);

        }

        @Override
        public Dimension getMinimumSize() {
            return getPreferredSize();
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2 = (Graphics2D) g;
            g2.setColor(Color.BLUE);
            g2.fillRect(0, 0, getWidth(), getHeight());
            g2.setColor(Color.WHITE);

            FontMetrics fontMetrics = g2.getFontMetrics();

            g2.drawString("This is a test", 20, fontMetrics.getAscent());
            g2.drawLine(10, 10, 290, 290);
        }
    }
}