How to post graphics on JPanel?

Question

I have a problem adding graphics to JPanel. If I changed the line from the .add panel (new graphics ()); to frame.add (new graphics ()); and don’t add a JPanel to the JFrame, a black rectangle appears on the JFrame. I just can't get the black rectangle to appear on JPannel and wondered if anyone could help me with this.

import java.awt.*; import java.awt.event.*; import javax.swing.*; public class Catch{ public class graphics extends JComponent{ public void paintComponent(Graphics g){ super.paintComponents(g); g.fillRect(200, 62, 30, 10); } } public void createGUI(){ final JFrame frame = new JFrame(); JPanel panel = new JPanel(); frame.setSize(500,500); frame.addMouseListener(new MouseAdapter(){ public void mouseClicked(MouseEvent e) { System.out.println(e.getPoint().getX()); System.out.println(e.getPoint().getY()); } }); panel.add(new graphics()); frame.add(panel); frame.setVisible(true); frame.setDefaultCloseOperation(frame.DISPOSE_ON_CLOSE); } public static void main(String[] args){ Catch GUI= new Catch(); GUI.createGUI(); } } 

Answer 1

The custom component was 0x0 px.

 import java.awt.*; import javax.swing.*; public class Catch { public class MyGraphics extends JComponent { private static final long serialVersionUID = 1L; MyGraphics() { setPreferredSize(new Dimension(500, 100)); } @Override public void paintComponent(Graphics g) { super.paintComponent(g); g.fillRect(200, 62, 30, 10); } } public void createGUI() { final JFrame frame = new JFrame(); JPanel panel = new JPanel(); panel.add(new MyGraphics()); frame.add(panel); frame.pack(); frame.setVisible(true); frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); } public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { @Override public void run() { Catch GUI = new Catch(); GUI.createGUI(); } }); } } 

Answer 2

Here is what you can see:

 import javax.swing.*; import java.awt.*; public class GraphicsOnJPanel extends JFrame { public GraphicsOnJPanel () { setSize (Toolkit.getDefaultToolkit ().getScreenSize ()); setResizable (false); setContentPane (new JPanel () { public void paint (Graphics g) { g.setColor (Color.RED); g.fillRect (100, 100, 100, 100); } } ); setVisible (true); } public static void main (String args[]) { new GraphicsOnJPanel (); } } 

Maybe this is helpful?