Custom JComponent does not appear in window

[KritSandvich]

Hello all!

For a personal project of mine, I have been trying to get a custom jcomponent into a jpanel into a frame. But it does not seem to be working; I only get a blank window. I have boiled it down to the following code:

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

public class Test extends JComponent
{
    public void paintComponent(Graphics g)
    {
        g.drawString("hello world", 100, 100);
    }
    
    public static void main(String[] args)
    {
        JFrame f = new JFrame("Test");
        f.setSize(500, 500);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        JPanel p = new JPanel();
        Test t = new Test();
        p.add(t);
        f.add(p);
        
        f.setVisible(true);
    }
}

Does anybody know the problem?
Thanks in advance!

[Fubarable]

The problem is that JPanels use FlowLayout by default and FlowLayout sizes contained components at their preferredSize. The preferredSize of your JComponent is 0,0. Try overriding getPreferredSize(...)

import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.Graphics;
 
public class Test extends JComponent
{
    public void paintComponent(Graphics g)
    {
        g.drawString("hello world", 100, 100);
    }

    @Override
    public Dimension getPreferredSize() {
       return new Dimension(300, 300);
    }
     
    public static void main(String[] args)
    {
        JFrame f = new JFrame("Test");
        // f.setSize(500, 500); // !! get rid of this !!
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         
        JPanel p = new JPanel();
        Test t = new Test();
        p.add(t);
        f.add(p);

        f.pack();  // !! add !!
         
        f.setVisible(true);
    }
}

Caveat: code neither compiled nor tested

[KritSandvich]

That did it! Thanks!

[Fubarable]

You're welcome!