Empty JFrame

I'm developing a main menu for an application with two drop down menus and 5 normal control buttons. I set the buttons up first and had them displaying (and the exit button working) but when I added the combo boxes the JFrame just shows nothing. And I can't work out why.

Code:

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/*
A rough working for a GUI interface
*/

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
// Import the GUI packages

public class Layout {
        public static void main(String[] args) {
                JFrame window = new JFrame();
                JPanel dropdowns = new JPanel();
                JPanel menu = new JPanel();
                JPanel content = new JPanel();
                // Declare the JFrame and menu and content panels

                window.setLayout(new BorderLayout(10,10));
                window.setVisible(true);
                window.setSize(600,200);
                window.setMinimumSize(new Dimension(600,200));
                window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                // Set the frame properties

                JComboBox to = new JComboBox();
                        to.addItem("Leicester"); to.addItem("Loughborough"); to.addItem("Nottingham"); to.addItem("Derby"); to.addItem("Lincoln");
                JComboBox from = new JComboBox();
                        from.addItem("Leicester"); from.addItem("Loughborough"); from.addItem("Nottingham"); from.addItem("Derby"); from.addItem("Lincoln");
                // Declare the drop down menus and add the options

                final JButton price = new JButton("Route Price");
                final JButton time = new JButton("Route Time");
                final JButton stops = new JButton("Route Stops");
                final JButton admin = new JButton("Admin");
                final JButton exit = new JButton("Exit");
                // Declare the main menu buttons

                class ButtonHandler implements ActionListener {
                        public void actionPerformed(ActionEvent e) {
                                JButton clicked = (JButton) e.getSource();
                                if(clicked == exit) {
                                        System.exit(0);
                                }
                                // Get the JButton the user clicked
                        }
                }
                // Create a class to handle the buttons

                ButtonHandler buttons = new ButtonHandler();
                price.addActionListener(buttons);
                time.addActionListener(buttons);
                stops.addActionListener(buttons);
                admin.addActionListener(buttons);
                exit.addActionListener(buttons);
                // Call the ButtonHandler class and apply it to the buttons

                menu.setLayout(new FlowLayout());
                menu.setVisible(true);
                // Set the menu properties

                dropdowns.setLayout(new FlowLayout());
                dropdowns.setVisible(true);
                // Set the dropdowns properties

                dropdowns.add(to); dropdowns.add(from);
                menu.add(price); menu.add(time); menu.add(stops); menu.add(admin); menu.add(exit);
                window.add(dropdowns);
                window.add(menu);
                // Add the buttons to the menu, and add the menu to the frame
        }
}

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Any help would be appreciated.

Or not. Got it solved by moving some of the code about. Not entirely sure why that worked.

Quote:

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Not entirely sure why that worked.

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By default a JFrame will use a BorderLayout (and you code also sets the layout be be a BorderLayout). When you don't specify where in the BorderLayout a component should be added, the component gets added to the CENTER.

Code:

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window.add(dropdowns);
window.add(menu);

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You are trying to add two components to the CENTER which won't work. Read the section from the Swing tutorial on How to Use Border Layout for proper usage of this layout manager.