Providing white space in a Swing GUI

Question

Using various LayoutManagers one can provide spacing between various components.

1.) BorderLayout :

• Overloaded Constructor : BorderLayout(int horizontalGap, int verticalGap)

• Getter and setter methods

  For Horizontal Spacing : BorderLayout.getHgap() and BorderLayout.setHgap(int hgap)

  For Vertical Spacing : BorderLayout.getVgap() and BorderLayout.setVgap()

2.) FlowLayout :

• Overloaded Constructor : FlowLayout(int align, int hgap, int vgap)

• Getter and setter methods

  For Horizontal Spacing : FlowLayout.getHgap() and FlowLayout.setHgap(int hgap)

  For Vertical Spacing : FlowLayout.getVgap() and FlowLayout.setVgap()

3.) GridLayout :

• Overloaded Constructor : GridLayout(int rows, int columns, int hgap, int vgap)

• Getter and setter methods

  For Horizontal Spacing : GridLayout.getHgap() and GridLayout.setHgap(int hgap)

  For Vertical Spacing : GridLayout.getVgap() and GridLayout.setVgap()

4.) GridBagLayout :

GridBagConstraints.insets

5.) CardLayout (example) :

CardLayout(int hGap, int vGap)

Example to display all constructors in action :

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

public class LayoutExample {

    private final int hGap = 5;
    private final int vGap = 5;

    private String[] borderConstraints = {
        BorderLayout.PAGE_START,
        BorderLayout.LINE_START,
        BorderLayout.CENTER,
        BorderLayout.LINE_END,
        BorderLayout.PAGE_END
    };

    private JButton[] buttons;

    private GridBagConstraints gbc;

    private JPanel borderPanel;
    private JPanel flowPanel;
    private JPanel gridPanel;
    private JPanel gridBagPanel;
    private JPanel cardPanel;

    public LayoutExample() {
        buttons = new JButton[16];
        gbc = new GridBagConstraints();
        gbc.anchor = GridBagConstraints.FIRST_LINE_START;   
        gbc.insets = new Insets(hGap, vGap, hGap, vGap);        
    }

    private void displayGUI() {
        JFrame frame = new JFrame("Layout Example");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        JPanel contentPane = new JPanel(
                        new GridLayout(0, 1, hGap, vGap));
        contentPane.setBorder(
            BorderFactory.createEmptyBorder(hGap, vGap, hGap, vGap));
        borderPanel = new JPanel(new BorderLayout(hGap, vGap));
        borderPanel.setBorder(
            BorderFactory.createTitledBorder("BorderLayout"));
        borderPanel.setOpaque(true);
        borderPanel.setBackground(Color.WHITE);
        for (int i = 0; i < 5; i++) {
            buttons[i] = new JButton(borderConstraints[i]);
            borderPanel.add(buttons[i], borderConstraints[i]);
        }
        contentPane.add(borderPanel);

        flowPanel = new JPanel(new FlowLayout(
                    FlowLayout.CENTER, hGap, vGap));
        flowPanel.setBorder(
            BorderFactory.createTitledBorder("FlowLayout"));
        flowPanel.setOpaque(true);
        flowPanel.setBackground(Color.WHITE);
        for (int i = 5; i < 8; i++) {
            buttons[i] = new JButton(Integer.toString(i));
            flowPanel.add(buttons[i]);
        }
        contentPane.add(flowPanel);

        gridPanel = new JPanel(new GridLayout(2, 2, hGap, vGap));
        gridPanel.setBorder(
            BorderFactory.createTitledBorder("GridLayout"));
        gridPanel.setOpaque(true);
        gridPanel.setBackground(Color.WHITE);
        for (int i = 8; i < 12; i++) {
            buttons[i] = new JButton(Integer.toString(i));
            gridPanel.add(buttons[i]);
        }
        contentPane.add(gridPanel);

        gridBagPanel = new JPanel(new GridBagLayout());
        gridBagPanel.setBorder(
            BorderFactory.createTitledBorder("GridBagLayout"));
        gridBagPanel.setOpaque(true);
        gridBagPanel.setBackground(Color.WHITE);
        buttons[12] = new JButton(Integer.toString(12));
        addComp(gridBagPanel, buttons[12], 0, 0, 1, 1
                            , GridBagConstraints.BOTH, 0.33, 0.5);
        buttons[13] = new JButton(Integer.toString(13));
        addComp(gridBagPanel, buttons[13], 1, 0, 1, 1
                            , GridBagConstraints.BOTH, 0.33, 0.5);
        buttons[14] = new JButton(Integer.toString(14));
        addComp(gridBagPanel, buttons[14], 0, 1, 2, 1
                            , GridBagConstraints.BOTH, 0.66, 0.5);
        buttons[15] = new JButton(Integer.toString(15));
        addComp(gridBagPanel, buttons[15], 2, 0, 1, 2
                            , GridBagConstraints.BOTH, 0.33, 1.0);
        contentPane.add(gridBagPanel);

        cardPanel = new JPanel(new CardLayout(hGap, vGap));
        cardPanel.setBorder(
            BorderFactory.createTitledBorder("CardLayout"));
        cardPanel.setOpaque(true);
        cardPanel.setBackground(Color.WHITE);
        cardPanel.add(getPanel(Color.BLUE));
        cardPanel.add(getPanel(Color.GREEN));
        contentPane.add(cardPanel);

        frame.setContentPane(contentPane);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    private JPanel getPanel(Color bColor) {
        JPanel panel = new JPanel(new FlowLayout(
                    FlowLayout.CENTER, hGap, vGap));
        panel.setOpaque(true);
        panel.setBackground(bColor.darker().darker());
        JButton swapperButton = new JButton("Next");
        swapperButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent ae) {
                CardLayout cardLayout = (CardLayout) cardPanel.getLayout();
                cardLayout.next(cardPanel);
            }
        });

        panel.add(swapperButton);

        return panel;
    }

    private void addComp(JPanel panel, JComponent comp
                                , int x, int y, int gWidth
                                    , int gHeight, int fill
                                        , double weightx, double weighty) {
        gbc.gridx = x;
        gbc.gridy = y;
        gbc.gridwidth = gWidth;
        gbc.gridheight = gHeight;
        gbc.fill = fill;
        gbc.weightx = weightx;
        gbc.weighty = weighty;      

        panel.add(comp, gbc);
    }

    public static void main(String[] args) {
        Runnable runnable = new Runnable(){
            @Override
            public void run() {
                new LayoutExample().displayGUI();
            }
        };
        EventQueue.invokeLater(runnable);
    }
}

OUTPUT :

There are a number of ways in a Swing GUI to provide a separation between components, and white space around components:

• JToolBar has the methods addSeparator() & addSeparator(Dimension).
• JMenu uses a spacing component better suited to menus, available through addSeparator().

But more generally, look to:

• The spacing as can be defined in the layout constructors.
• Borders.

Here is an example of using the layout separator hGap & vGap values & borders (specifically an EmptyBorder) to provide 'white' (actually shown as red to make it very obvious) space. Adjust the spinners to see the result.

import java.awt.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import javax.swing.event.*;

public class WhiteSpace {

    private JPanel gui = null;
    private BorderLayout mainLayout = 
        new BorderLayout(0, 0);
    private final FlowLayout buttonLayout = 
            new FlowLayout(FlowLayout.CENTER, 0, 0);
    private final JPanel buttonPanel = new JPanel(buttonLayout);
    private final SpinnerNumberModel hModel = 
            new SpinnerNumberModel(0, 0, 15, 1);
    private final SpinnerNumberModel vModel = 
            new SpinnerNumberModel(0, 0, 15, 1);
    private final SpinnerNumberModel hBorderModel = 
            new SpinnerNumberModel(0, 0, 15, 1);
    private final SpinnerNumberModel vBorderModel = 
            new SpinnerNumberModel(0, 0, 15, 1);
    private ChangeListener changeListener;

    public Container getGui() {
        if (gui == null) {
            gui = new JPanel(mainLayout);
            gui.setBackground(Color.RED);

            JTree tree = new JTree();
            tree.setVisibleRowCount(10);
            for (int ii = tree.getRowCount(); ii > -1; ii--) {
                tree.expandRow(ii);
            }
            gui.add(new JScrollPane(
                    tree,
                    JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
                    JScrollPane.HORIZONTAL_SCROLLBAR_NEVER),
                    BorderLayout.LINE_START);
            gui.add(new JScrollPane(new JTextArea(10, 30)));

            gui.add(buttonPanel, BorderLayout.PAGE_START);

            changeListener = (ChangeEvent e) -> {
                int hGap = hModel.getNumber().intValue();
                int vGap = vModel.getNumber().intValue();
                int hBorder = hBorderModel.getNumber().intValue();
                int vBorder = vBorderModel.getNumber().intValue();
                adjustWhiteSpace(hGap, vGap, hBorder, vBorder);
            };

            addModel("H Gap", hModel);
            addModel("V Gap", vModel);
            addModel("H Border", hBorderModel);
            addModel("V Border", vBorderModel);
        }

        return gui;
    }

    private void addModel(String label, SpinnerNumberModel model) {
        buttonPanel.add(new JLabel(label));
        final JSpinner spinner = new JSpinner(model);
        spinner.addChangeListener(changeListener);
        buttonPanel.add(spinner);
    }

    private void adjustWhiteSpace(
            int hGap, int vGap, int hBorder, int vBorder) {
        mainLayout.setHgap(hGap);
        mainLayout.setVgap(vGap);
        buttonLayout.setHgap(hGap);
        gui.setBorder(new EmptyBorder
                (vBorder, hBorder, vBorder, hBorder));
        Container c = gui.getTopLevelAncestor();
        if (c instanceof Window) {
            Window w = (Window) c;
            w.pack();
        }
    }

    public static void main(String[] args) {
        Runnable r = () -> {
            WhiteSpace ws = new WhiteSpace();
            Container gui1 = ws.getGui();
            JFrame f = new JFrame("White (OK Red) Space");
            f.add(gui1);
            f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
            f.setLocationByPlatform(true);
            f.setResizable(false);
            f.pack();
            f.setVisible(true);
        };
        SwingUtilities.invokeLater(r);
    }
}

When you use BoxLayout, Box.createVerticalGlue() method can help you to make some white space.

Another method is BorderFactory.createEmptyBorder(int top, int left, int bottom, int right). It can help you to make some white space around component.

Thanks for Andrew Thompson's remind.I've revised BoxLayout in recent days and I find that Box.createVerticalGlue() can add some white space depend on the panel's size and you can not set the explicit pixel value of the length of white space.But Box.createVerticalStrut() can do that. Here is a MCTaRE and show the effect of those two methods.

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

public class WhiteSpace extends JFrame{
    static WhiteSpace whiteSpace;
    DemoPanel demoPanel;
    boolean withGlue;
    JSpinner spinner;

    public WhiteSpace(){
        initialWindow();
        demoPanel = new DemoPanel();
        ActionPanel actionPanel = new ActionPanel();

        setLayout(new BorderLayout());

        getContentPane().add(actionPanel,BorderLayout.NORTH);
        getContentPane().add(demoPanel,BorderLayout.CENTER);
            setVisible(true);
    }

    public void initialWindow(){
        setSize(220, 300);
        setTitle("White Space");
        setResizable(false);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        //Show the window in the middle of the screen
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                whiteSpace = new WhiteSpace();
            }
        };
        SwingUtilities.invokeLater(runnable);
    }

    class DemoPanel extends JPanel{
        //Show the vertical white space between label1 and label2
        JLabel label1;
        JLabel label2;
        public void initialDemoPanel(){
            setBorder(BorderFactory.createTitledBorder(getBorder(), "DemoPanel", TitledBorder.LEADING, TitledBorder.TOP, new Font("Default",Font.PLAIN,10), Color.gray));
            setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));

            label1 = new JLabel("This is first line");
            label2 = new JLabel("This is second line");
        }

        public DemoPanel(){
            initialDemoPanel();
            add(label1);
            if(withGlue){
                add(Box.createVerticalGlue());
            }
            add(label2);
        }

        public DemoPanel(int strutValue){
            initialDemoPanel();
            add(label1);
            add(Box.createVerticalStrut(strutValue));
            add(label2);
        }
    }

    class ActionPanel extends JPanel{
        public ActionPanel(){
            setBorder(BorderFactory.createTitledBorder(getBorder(), "ActionPanel", TitledBorder.LEADING, TitledBorder.TOP, new Font("Default",Font.PLAIN,10), Color.gray));

            setLayout(new BoxLayout(this,BoxLayout.X_AXIS));
            JRadioButton glueButton = new JRadioButton("With Glue");
            glueButton.addActionListener(new glueButtonListener());
            add(glueButton);

            add(Box.createHorizontalStrut(10));
            //To create horizontal white space
            JLabel strutLabel = new JLabel("Strut Value");
            add(strutLabel);
            spinner = new JSpinner(new SpinnerNumberModel(0,0,50,1));
            spinner.addChangeListener(new spinnerListener());
            add(spinner);
            //public SpinnerNumberModel(Number value,Comparable minimum,Comparable maximum,Number stepSize)
        }
    }

    class glueButtonListener implements ActionListener{
        @Override
        public void actionPerformed(ActionEvent e) {
            spinner.setValue(new Integer(0));
            withGlue = (withGlue == true ? false:true);
            whiteSpace.getContentPane().remove(demoPanel);
            demoPanel = new DemoPanel();
            whiteSpace.getContentPane().add(demoPanel,BorderLayout.CENTER);
            whiteSpace.getContentPane().validate();
        }
    }

    class spinnerListener implements ChangeListener{

        @Override
        public void stateChanged(ChangeEvent e) {
            int strutValue = (Integer) spinner.getValue();
            whiteSpace.getContentPane().remove(demoPanel);
            demoPanel = new DemoPanel(strutValue);
            whiteSpace.getContentPane().add(demoPanel,BorderLayout.CENTER);
            whiteSpace.getContentPane().validate();
        }
    }
}

Box.createHorizontalGlue() and Box.createHorizontalStrut(int height) can be used too. Besides, Box.createRigidArea(Dimension d) has the ability too create white space too.

MigLayout has multiple ways of creating space. (A space is called a gap in this layout.) Gaps can be created at the highest level with layout constraints, it is possible to create gaps between rows and column and gaps can be also set between individual components with component constraints. There are also specific gaps around the borders of a container called insets which have their own specific keyword to be set.

The following example creates all these kinds of gaps:

package com.zetcode;

import java.awt.EventQueue;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import net.miginfocom.swing.MigLayout;


public class MigLayoutGaps2 extends JFrame {

    public MigLayoutGaps2() {

        initUI();

        setTitle("Gaps");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
    }

    private void initUI() {

        JPanel base = new JPanel(new MigLayout("flowy, ins 30, gap 15"));
        setContentPane(base);

        JPanel pnl1 = new JPanel();
        pnl1.setBorder(
                BorderFactory.createTitledBorder("Grid gaps")
        );

        pnl1.setLayout(new MigLayout("gap 5 5, ins 10, wrap 3"));

        pnl1.add(new JButton("1"));
        pnl1.add(new JButton("2"));
        pnl1.add(new JButton("3"));
        pnl1.add(new JButton("4"));
        pnl1.add(new JButton("5"));
        pnl1.add(new JButton("6"));

        JPanel pnl2 = new JPanel();
        pnl2.setBorder(
                BorderFactory.createTitledBorder("Column gaps")
        );

        pnl2.setLayout(new MigLayout("wrap 3", "[]10[]"));

        JLabel lbl1 = new JLabel();
        lbl1.setBorder(
            BorderFactory.createEtchedBorder()
        );

        JLabel lbl2 = new JLabel();
        lbl2.setBorder(
            BorderFactory.createEtchedBorder()
        );

        JLabel lbl3 = new JLabel();
        lbl3.setBorder(
            BorderFactory.createEtchedBorder()
        );        

        pnl2.add(lbl1, "w 40, h 110");
        pnl2.add(lbl2, "w 40, h 110");
        pnl2.add(lbl3, "w 40, h 110");

        JPanel pnl3 = new JPanel();
        pnl3.setBorder(
                BorderFactory.createTitledBorder("Row gaps")
        );

        pnl3.setLayout(new MigLayout("wrap", "", "[]15[]"));

        JLabel lbl4 = new JLabel();
        lbl4.setBorder(
            BorderFactory.createEtchedBorder()
        );

        JLabel lbl5 = new JLabel();
        lbl5.setBorder(
            BorderFactory.createEtchedBorder()
        );

        JLabel lbl6 = new JLabel();
        lbl6.setBorder(
            BorderFactory.createEtchedBorder()
        );        

        pnl3.add(lbl4, "w 150, h 20");
        pnl3.add(lbl5, "w 150, h 20");
        pnl3.add(lbl6, "w 150, h 20");        

        JPanel pnl4 = new JPanel();
        pnl4.setBorder(
                BorderFactory.createTitledBorder("Component gaps")
        );

        pnl4.setLayout(new MigLayout());

        pnl4.add(new JLabel("Name:"), "gapright 5");
        pnl4.add(new JTextField(10), "gapbottom 20, gaptop 20");

        base.add(pnl1);
        base.add(pnl2);
        base.add(pnl3);
        base.add(pnl4);

        pack();
    }

    public static void main(String[] args) {

        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                MigLayoutGaps2 ex = new MigLayoutGaps2();
                ex.setVisible(true);
            }
        });
    }
}

We have four panels in the layout. Each of this panels has a MigLayout manager.

JPanel base = new JPanel(new MigLayout("flowy, ins 30, gap 15"));

This line creates container insets and vertical gaps between panels.

pnl1.setLayout(new MigLayout("gap 5 5, ins 10, wrap 3"));

Here we apply gaps for the whole grid structure and also set container gaps.

pnl2.setLayout(new MigLayout("wrap 3", "[]10[]"));

This line creates gaps between columns.

pnl3.setLayout(new MigLayout("wrap", "", "[]15[]"));

Row gaps are defined with this code.

pnl4.add(new JLabel("Name:"), "gapright 5");
pnl4.add(new JTextField(10), "gapbottom 20, gaptop 20");

Finally, it is possible to create gaps between individual components.