How do I create JTree with different icons for each node?

By Wayan in Java Swing 3 Comments

The example below demonstrates you how to create a JTree that have a different icons for each node of the tree.

package org.kodejava.example.swing;

import javax.swing.*;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreeCellRenderer;
import java.awt.*;
import java.net.URL;

public class JTreeDifferentNodeIcon extends JFrame {
    public JTreeDifferentNodeIcon() throws HeadlessException {
        initializeUI();
    }

    private void initializeUI() {
        setSize(200, 400);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        DefaultMutableTreeNode root = new DefaultMutableTreeNode("Countries");
        DefaultMutableTreeNode asia = new DefaultMutableTreeNode("Asia");
        Country[] countries = new Country[]{
                new Country("India", "/flags/in.png"),
                new Country("Singapore", "/flags/sg.png"),
                new Country("Indonesia", "/flags/id.png"),
                new Country("Vietnam", "/flags/vn.png"),
        };

        for (Country country : countries) {
            DefaultMutableTreeNode node = new DefaultMutableTreeNode(country);
            asia.add(node);
        }

        DefaultMutableTreeNode northAmerica = new DefaultMutableTreeNode("North America");
        countries = new Country[]{
                new Country("United States", "/flags/us.png"),
                new Country("Canada", "/flags/ca.png")
        };

        for (Country country : countries) {
            DefaultMutableTreeNode node = new DefaultMutableTreeNode(country);
            northAmerica.add(node);
        }

        DefaultMutableTreeNode southAmerica = new DefaultMutableTreeNode("South America");
        countries = new Country[]{
                new Country("Brazil", "/flags/br.png"),
                new Country("Argentina", "/flags/ar.png"),
                new Country("Uruguay", "/flags/uy.png")
        };
        for (Country country : countries) {
            DefaultMutableTreeNode node = new DefaultMutableTreeNode(country);
            southAmerica.add(node);
        }

        DefaultMutableTreeNode europe = new DefaultMutableTreeNode("Europe");
        countries = new Country[]{
                new Country("United Kingdom", "/flags/gb.png"),
                new Country("Germany", "/flags/de.png"),
                new Country("Spain", "/flags/es.png"),
                new Country("France", "/flags/fr.png"),
                new Country("Italy", "/flags/it.png")
        };
        for (Country country : countries) {
            DefaultMutableTreeNode node = new DefaultMutableTreeNode(country);
            europe.add(node);
        }

        root.add(asia);
        root.add(northAmerica);
        root.add(southAmerica);
        root.add(europe);

        final JTree tree = new JTree(root);
        tree.setCellRenderer(new CountryTreeCellRenderer());

        JScrollPane pane = new JScrollPane(tree);
        pane.setPreferredSize(new Dimension(200, 400));

        getContentPane().setLayout(new BorderLayout());
        getContentPane().add(pane, BorderLayout.CENTER);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new JTreeDifferentNodeIcon().setVisible(true);
            }
        });
    }

    class CountryTreeCellRenderer implements TreeCellRenderer {
        private JLabel label;

        CountryTreeCellRenderer() {
            label = new JLabel();
        }

        public Component getTreeCellRendererComponent(JTree tree, Object value, boolean selected, boolean expanded,
                                                      boolean leaf, int row, boolean hasFocus) {
            Object o = ((DefaultMutableTreeNode) value).getUserObject();
            if (o instanceof Country) {
                Country country = (Country) o;
                URL imageUrl = getClass().getResource(country.getFlagIcon());
                if (imageUrl != null) {
                    label.setIcon(new ImageIcon(imageUrl));
                }
                label.setText(country.getName());
            } else {
                label.setIcon(null);
                label.setText("" + value);
            }
            return label;
        }
    }

    class Country {
        private String name;
        private String flagIcon;

        Country(String name, String flagIcon) {
            this.name = name;
            this.flagIcon = flagIcon;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getFlagIcon() {
            return flagIcon;
        }

        public void setFlagIcon(String flagIcon) {
            this.flagIcon = flagIcon;
        }
    }
}

Here is the result of our program above:

JTree with different icon for each node

Flag icons provided by FamFamFam Flag Icons.

Wayan

Programmer, runner, recreational diver, live in the island of Bali, Indonesia. Mostly programming in Java, creating web based application with Spring Framework, Hibernate / JPA.

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3 Comments

  3. Hi Hades,

    If the imageUrl is null it means that it cannot find the flags icon. You need to place the icon under the resources directory.

    ├── pom.xml
└── src
    └── main
        ├── java
        │   └── org
        │       └── kodejava
        │           └── example
        │               └── swing
        │                   └── JTreeDifferentNodeIcon.java
        └── resources
            └── flags
                ├── ar.png
                ├── br.png

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