How can I align elements in JPanels / JFrames?

Question

I'm completely new to using the GUI in java, so I'm having a bit of trouble figuring out how to align everything that I need to. I have to panels in my JFrame that I need to align (One to the left, one to the right) and a few buttons in one of the panels that I need to be centered in the panel. Here is my code.

package application;

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import java.io.*;
import java.nio.*;
import java.util.*;

public class Main extends JPanel 
{
    public static void main(String[] args)
    { 
        //set the ui to the native OS
        try
        { 
            UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
        }catch(ClassNotFoundException | InstantiationException | IllegalAccessException 
        | UnsupportedLookAndFeelException e)                                   
        {
        }

        JFrame frame = new JFrame("Application Name");
        Menu menu = new Menu();
        JPanel iconPanel = new JPanel();
        final JPanel grid = new JPanel(new FlowLayout());
        JButton firewallButton = new JButton("Firewall");
        JButton networkButton = new JButton("Network");
        JButton printerButton = new JButton("Printer");

        int iconPanelSizeX;
        int iconPanelSizeY;
        int gridSizeX;
        int gridSizeY;
        int gridPosition;

        //frame setting
        frame.setSize(800, 600);
        frame.setMinimumSize(new Dimension(800, 600));
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

        //add grid and iconPanel JPanels to the frame
        frame.add(iconPanel);
        iconPanel.add(firewallButton);
        iconPanel.add(networkButton);
        iconPanel.add(printerButton);
        frame.add(grid);        

        //iconPanel settings
        iconPanel.setBorder(BorderFactory.createLoweredSoftBevelBorder());
        iconPanel.setBackground(Color.gray);
        iconPanel.setLayout(new FlowLayout());
        iconPanel.setSize(new Dimension(100, 600));
        iconPanel.setVisible(true);

        //grid setting
        grid.setBackground(Color.red);
        grid.setSize(new Dimension(700, 600));
        grid.setVisible(true);

        //this is for resizing components when the user resizes the window
        int counter = 0;
        while(counter == 0)
        {
            firewallButton.setSize(new Dimension(iconPanel.getWidth(), 50));
            networkButton.setSize(new Dimension(iconPanel.getWidth(), 50));
            printerButton.setSize(new Dimension(iconPanel.getWidth(), 50));
            iconPanelSizeX = frame.getWidth() / 10;
            iconPanelSizeY = frame.getHeight();
            gridSizeX = (frame.getWidth() / 10) * 9;
            gridSizeY = frame.getHeight();
            iconPanel.setSize(new Dimension(iconPanelSizeX, iconPanelSizeY));
            grid.setSize(new Dimension(gridSizeX, gridSizeY));
        }
    }
}

As you can see, the second JPanel (grid) doesn't line up with the right side of the frame, and the buttons inside iconTray don't center either. I realize these are both probably simple layout fixes, but I have no clue where to start.

Answer 1

For simple splitting of JFrame you can use GridLayout with 1 row and 2 colums.

frame.setLayout(new GridLayout(1,2,3,3)); //3,3 are gaps
frame.add(grid);
frame.add(iconPanel);

For centering components in panels you can use FlowLayout which is by default set on JPanels :

Doing it manualy:

grid.setLayout(new FlowLayout()); //Centered components

grid.setLayout(new FlowLayout(FlowLayout.LEFT,3,3)); //Components aligned to left

grid.setLayout(new FlowLayout(FlowLayout.RIGHT,3,3)); //Components aligned to right

This is how it looks:

Also, few observations:

• Never call setXXXSize() methods for your components;

• Try to avoid calling setSize(); for JFrame , call pack(); instead;

• Call setVisible(true); in the end of code;

All your huge code can be "stripped" to this:

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


public class Main extends JPanel
{
    public static void main(String[] args)
    {
        JFrame frame = new JFrame("Application Name");
        JPanel iconPanel = new JPanel();
        JPanel grid = new JPanel(new FlowLayout());
        JButton firewallButton = new JButton("Firewall");
        JButton networkButton = new JButton("Network");
        JButton printerButton = new JButton("Printer");


        frame.add(iconPanel);
        iconPanel.add(firewallButton);
        iconPanel.add(networkButton);
        iconPanel.add(printerButton);
        grid.setBackground(Color.GREEN);

        frame.setLayout(new GridLayout(1,2,3,3));
        frame.add(grid);
        frame.add(iconPanel);


        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

Answer 2

how to align buttons vertically?

This example uses a vertical Box in the WEST area of the frame's default BorderLayout :

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

/** @see http://stackoverflow.com/a/14927280/230513 */
public class Main {

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                display();
            }
        });
    }

    private static void display() throws HeadlessException {
        JFrame frame = new JFrame("Application Name");
        JButton firewallButton = new JButton("Firewall");
        JButton networkButton = new JButton("Network");
        JButton printerButton = new JButton("Printer");

        //iconPanel settings
        Box iconPanel = new Box(BoxLayout.Y_AXIS);
        iconPanel.add(firewallButton);
        iconPanel.add(networkButton);
        iconPanel.add(printerButton);
        iconPanel.setBackground(Color.gray);
        iconPanel.setVisible(true);
        frame.add(iconPanel, BorderLayout.WEST);

        //grid setting
        JPanel grid = new JPanel() {

            @Override
            // arbitrary placeholder size
            public Dimension getPreferredSize() {
                return new Dimension(320, 230);
            }
        };
        grid.setBackground(Color.red);
        frame.add(grid, BorderLayout.CENTER);

        //frame setting
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

Answer 3

I suggest you take some time going through A Visual Guide to Layout Managers . This will help you become familiar with the layout managers which are available with the Standard API. It takes some experience and hard work to figure out which of these is the right tool to get the exact look you want. Once you become comfortable with what is available from the Standard API, you should also look around for third-party Layout Manager APIs which provide other options.

Answer 4

I have to panels in my JFrame that I need to align (One to the left, one to the right) and a few buttons in one of the panels that I need to be centered in the panel. Here is my code.

I realize these are both probably simple layout fixes, but I have no clue where to start.

Use more complex layout than simple FlowLayout which you actually using. I suggest to you use

• GridBagLayout
• BoxLayout

Check references here