Question

I have the following code. Class KochSnowflakesMenu is a grid JPanel with three buttons. Class KochSnowflakesDraw currently draws a circle using drawOval:

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

public class KochSnowflakes
{
    public static void main(String[] args)
    {
        JFrame frame = new JFrame("Koch Snowflakes");
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setBounds(0,0, 600, 425);
        frame.setBackground(Color.BLACK);
        frame.setResizable(false);
        frame.setLayout(null);

        // Create the button interface
        frame.add(new KochSnowflakesMenu());
        frame.add(new KochSnowflakesDraw());
        frame.repaint();
    }
}

This works if I comment out frame.setResizable(false). When I don’t the buttons don’t appear. Why is that? As you can see, I have tried using repaint(). I had previously the problem that the buttons would not show up until I manually resized the window…

Also, as a bonus question, if anyone can tell me how to get the dimensions of a JPanel that would be great. The reason why I can’t use a resizable layout manager such as BorderLayout, which really is what I want to use, is that I can’t figure out the dimension of the JPanel that occupies the center (and hence have no idea how to large to draw the things I’m drawing).

EDIT:
As requested, here is the KockSnowflakesMenu class:

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

public class KochSnowflakesMenu extends JPanel
{
    public KochSnowflakesMenu()
    {
        setLayout(new GridLayout(3,1));
        setBounds(0,0,200,400);

        JButton button_red = new JButton("Red");
        JButton button_yellow = new JButton("Yellow");
        JButton button_blue = new JButton("Blue");

        add(button_red);
        add(button_yellow);
        add(button_blue);
    }
}

And, just to be sure I didn’t mess something up with KochSnowflakesDraw, here’s that class as well:

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

public class KochSnowflakesDraw extends JPanel
{
    public KochSnowflakesDraw()
    {
        setLayout(null);
        setBounds(200, 0, 400, 400);
    }

    public void paintComponent(Graphics g)
    {
        g.setColor(Color.RED);
        g.drawOval(0,0,400, 400);
    }
}

Answer 1

Adding more info to the previous answers…
The size is random until the component is drawn so make sure you have a setVisible(true) on your frame. Here’s your code w/some modifications that let you use the BorderLayout and get the size of your drawing panel. I substituted some fake buttons for your interfaces but you’ll get the drift.

JFrame frame = new JFrame("Koch Snowflakes");
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setBounds(0,0, 600, 425);
frame.setBackground(Color.BLACK);
frame.setResizable(false);
frame.setLayout(new BorderLayout());

JPanel buttons = new JPanel(new FlowLayout());
buttons.add(new JButton("MENU"));
buttons.add(new JButton("DRAW"));
frame.add(buttons, BorderLayout.SOUTH);

JPanel drawArea = new JPanel();
drawArea.setBackground(Color.BLUE);
frame.add(drawArea, BorderLayout.CENTER);
frame.setVisible(true);
Dimension drawAreaDim = drawArea.getSize();
System.out.println(drawAreaDim);