以下示例演示了如何为JTree树的每个节点创建一个具有不同图标的。
package org.nhooo.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; } } }
运行上面程序
FamFamFam标志图标提供的标志图标。