Why am I not able to "draw" on my JFrame?

Question

I am trying to draw on my JFrame, but I can't get my super.paintComponents(g); to work. Also, nothing is drawing on my JFrame when I tell it to in my paintComponent() method.

Here is the code:

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

public class MTGSAMPServerReference extends JFrame implements ActionListener {

    public static Toolkit tk = Toolkit.getDefaultToolkit(); 
    static int ScrnWidth = ((int) tk.getScreenSize().getWidth());
    static int ScrnHeight = ((int) tk.getScreenSize().getHeight());
    private static final long serialVersionUID = 1L;
    private static JList list1;
    private static JButton next;

    public MTGSAMPServerReference() {
        // set flow layout for the frame
        this.getContentPane().setLayout(new FlowLayout(FlowLayout.LEADING));
        Object[]mainData = {"Vehicles", "Bikes/Bicycles", "Boats", "Houses", "Businesses", "Objects", "Jobs", "Ranks", "Licenses", "VIP"};
        JPanel controls = new JPanel(new BorderLayout(5,5));
        list1 = new JList<Object>(mainData);
        list1.setVisibleRowCount(10);
        next = new JButton("Next");
        next.addActionListener(this);
        controls.add(new JScrollPane(list1));
        controls.add(next, BorderLayout.PAGE_END);
        controls.setBorder(new EmptyBorder(25,25,0,0));
        add(controls);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        if (e.getActionCommand().equals("Next")) {
            int index = list1.getSelectedIndex();
            System.out.println("Index Selected: " + index);
            String s = (String) list1.getSelectedValue();
            System.out.println("Value Selected: " + s);
        }
    }

    public void createAndShowGUI() {
        //Create and set up the window.
        JFrame f = new MTGSAMPServerReference();
        //Display the window.
        f.pack();
        f.setVisible(true);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setSize(1200, 800);
        f.setLocationRelativeTo(null);
        list1.setSize(250, 250);
        list1.setLocation(0, 0);
        next.setSize(75, 25);
        next.setLocation(251, 276);
        MTGSAMPServerReference.this.repaint();
    }

    protected void paintComponent(Graphics g) {
        //super.paintComponent(g);  <<  Can't seem to get this to work.
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2.drawRect(0, 0, 50, 50);
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
            MTGSAMPServerReference gui = new MTGSAMPServerReference();
            gui.createAndShowGUI();
            }
        });
    }
}

I have worked with paintComponent() before, but still can't seem to figure out what I am doing wrong. I know that it has got to be a simple fix, but can't spot it for the life of me. Any ideas?

Any and all help is appreciated.

Thanks in advance!

Answer 1

Use the @Override annotation on your paintComponent method for a rude surprise. This is why using this annotation is very helpful, since it will flag you at compile time if you are not overriding a method when you think that you should be.

Solution: never "paint" in a JFrame for many reasons. Instead do what the tutorials tell you to do -- paint in a JPanel or JComponent's paintComponent(...) method. If you search this site you will find that we have told many folks here the same thing, and in fact I suggest that you do just that. I wouldn't be surprised if this question is closed as a duplicate since this is a fairly common question.

Note this won't "work" (and actually won't compile):

super.paintComponent(g);  <<  Can't seem to get this to work.

for the same reason -- there is no super.paintComponent(g) for a JFrame.

Also, regarding,

I have worked with paintComponent() before, but still can't seem to figure out what I am doing wrong.

But if you look at your prior code, you'll see that this method was never used directly in a JFrame, and nor should it.