JPanel is not displaying in my JFrame

Question

so I'm playing with JPanels and JFrames and I'm noticing that the JPanel I created is not showing displaying when I add it to a Jframe object. Note, that when I created a JPanel in my Jframe constructor giving the jpanel parameters before being added to the Jframe, it worked. However now I'm using a JPanel object I created and it's not working anymore. This is what I have done.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Point;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class MyGui extends JFrame {

    MyMouseListener listen = new MyMouseListener();

    public MyGui() {
        setSize(500, 500);
        //setLayout(new BoxLayout(this, BoxLayout.X_AXIS));
        getContentPane().setBackground(Color.WHITE);
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });
        Panel panel = new Panel();
        add(panel, BorderLayout.WEST);
        //setVisible(true);
        show();
    }

    public static void main(String[] a) {
        MyGui gui = new MyGui();
    }
}

class Panel extends JPanel {

    MyMouseListener listen = new MyMouseListener();

    public Panel() {
        setPreferredSize(new Dimension(300, 300));
        addMouseListener(listen);
        setBackground(Color.YELLOW);
        setLayout(new GridLayout(3, 1));
    }

    public void paint(Graphics g) {
        super.paintComponents(g);
        g.drawOval((int) Math.round(listen.p.getX()),
                (int) Math.round(listen.p.getX()), 1, 1);
    }
}

class MyMouseListener implements MouseListener {

    Point p = new Point();

    @Override
    public void mouseClicked(MouseEvent e) {
        System.out.println("Mouse was clicked");
    }

    @Override
    public void mousePressed(MouseEvent e) {
        p = e.getPoint();
        System.out.println(p);
    }

    @Override
    public void mouseReleased(MouseEvent e) {
    }

    @Override
    public void mouseEntered(MouseEvent e) {
    }

    @Override
    public void mouseExited(MouseEvent e) {
    }
}

EDIT: Actually I think I've found the error. The JPanel has it's paint method which when deleted allows the Jframe to show the panel. However I need to be able to draw stuff on the JPanel.

Call pack() or setSize() before showing the frame. If you add the panel after showing call revalidate(); repaint(); — StanislavL, Sep 18 '13 at 12:30
The only thing I changed in your code to see your panel was to change `super.paintComponents(g);` to `super.paintComponent(g);`. That still leave out your oval that isn't painted. — Jonathan Drapeau, Sep 18 '13 at 12:49
@JonathanDrapeau So it looked liked this? public void paintComponent (Graphics g){ super.paintComponent(g); g.drawOval((int)Math.round(listen.p.getX()), (int)Math.round(listen.p.getX()), 1, 1); } — Michael Nana, Sep 18 '13 at 12:54
`public void paint (Graphics g){ super.paintComponent(g); g.drawOval((int)Math.round(listen.p.getX()), (int)Math.round(listen.p.getX()), 1, 1); }`, didn't mention changing anything else but that line. :) — Jonathan Drapeau, Sep 18 '13 at 12:55
@MichaelNana : Please have a look at this [answer](http://stackoverflow.com/a/11372350/1057230) — nIcE cOw, Sep 18 '13 at 14:03

Naveen · Accepted Answer · 2013-09-18T12:41:56.957

4

its

super.paintComponent(g);

Advice:

1)You are making things unnecessarily complex. e.g to close the window you should use

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

instead of the call to System.exit(0); and using window listeners

2)As said by @mKorbel , you should use SwingUtilities.invokeLater to start your gui as Java GUIs are supposed to run on EDT(Event Dispatch Thread) and should not run on main thread.

edited Sep 18 '13 at 12:41

answered Sep 18 '13 at 12:36

Naveen

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Thanks for your suggestions. I have apdated my code with the changes. Anyway, taking out super.paintComponent(g) still doesn't make the JPanel visible in the JFrame. – Michael Nana Sep 18 '13 at 12:47
You don't have to take out anything.Just remove the **s** in the line `super.paintComponents(g);` inside your `paint`.Now it should look like `super.paintComponent(g);`.Then,it runs fine – Naveen Sep 18 '13 at 12:50
I did that too and it still doesn't work. public void paintComponent (Graphics g){ super.paintComponent(g); g.drawOval((int)Math.round(listen.p.getX()), (int)Math.round(listen.p.getX()), 1, 1); } – Michael Nana Sep 18 '13 at 12:52

score 2 · Answer 2 · answered Sep 18 '13 at 12:34

2

1) super.paintComponents(g); inside paint() could be

public void paintComponent(Graphics g) {
    super.paintComponent(g);

    ....
}

2) don't to set any size setSize(500,500); or setPreferredSize(new Dimension(300, 300));, to use pack() and then (uncomment) setVisible(true) for JFrame and to override getPreferredSize() for JPanel

3) MyGui gui=new MyGui(); inside public static void main(String []a){, should be wrapped into invokeLater, more see in Oracle tutorial Initial Thread

answered Sep 18 '13 at 12:34

mKorbel

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There's a preferred size set to the `JPanel`, making `pack()` and `setVisible` work correctly. – Jonathan Drapeau Sep 18 '13 at 12:41
1

@Jonathan Drapeau [agree with final result, but isn't about good coding practicies](http://stackoverflow.com/a/9258934/714968) – mKorbel Sep 18 '13 at 12:44
@mKorbel Are you talking about the paintComponent inside the JPanel? because I have included the call to the super and commented it out and on both occasions the JPanel still didn't show up. – Michael Nana Sep 18 '13 at 12:51
@Michael Nana see my linked code in above comment addressed to Jonathan Drapeau – mKorbel Sep 18 '13 at 12:55

score 1 · Answer 3 · answered Sep 18 '13 at 12:33

1

Did you try to set the layout manager and add the panel to the contentPane instead of the JFrame itself ?

getContentPane().setLayout(new BorderLayout());
getContentPane().add(panel, BorderLayout.WEST);

answered Sep 18 '13 at 12:33

Hugo G.

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1

You should always add your Panel to the contentPane anyway. http://docs.oracle.com/javase/tutorial/uiswing/components/toplevel.html – Hugo G. Sep 18 '13 at 13:28

score 0 · Answer 4 · answered Sep 18 '13 at 12:34

0

Default Layout manager for frame is FlowLayout not BorderLayout. Try to setLayout(new BorderLayout()) in your MyGui contructor.

answered Sep 18 '13 at 12:34

Antoniossss

31,590
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Default `Layout` for `JFrame` is `BorderLayout` and not `FlowLayout` – nIcE cOw Sep 18 '13 at 12:57

score 0 · Answer 5 · edited Oct 29 '20 at 09:55

0

You didn't set a Layout to your content pane. Try something like getContentPane.setLayout(new Layout())

View the oracle docs for details about layout managers: http://docs.oracle.com/javase/tutorial/uiswing/layout/layoutlist.html

Hope this helps

edited Oct 29 '20 at 09:55

jMan

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answered Sep 18 '13 at 12:34

Sorontur

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JPanel is not displaying in my JFrame

5 Answers5