Java tutorial
/* * Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * - Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * - Neither the name of Sun Microsystems nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ import java.awt.BorderLayout; import java.awt.Toolkit; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.BorderFactory; import javax.swing.Box; import javax.swing.BoxLayout; import javax.swing.DefaultListModel; import javax.swing.JButton; import javax.swing.JComponent; import javax.swing.JFrame; import javax.swing.JList; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JSeparator; import javax.swing.JTextField; import javax.swing.ListSelectionModel; import javax.swing.SwingConstants; import javax.swing.event.DocumentEvent; import javax.swing.event.DocumentListener; import javax.swing.event.ListSelectionEvent; import javax.swing.event.ListSelectionListener; /* ListDemo.java requires no other files. */ public class ListDemo extends JPanel implements ListSelectionListener { private JList list; private DefaultListModel listModel; private static final String hireString = "Hire"; private static final String fireString = "Fire"; private JButton fireButton; private JTextField employeeName; public ListDemo() { super(new BorderLayout()); listModel = new DefaultListModel(); listModel.addElement("Debbie Scott"); listModel.addElement("Scott Hommel"); listModel.addElement("Sharon Zakhour"); // Create the list and put it in a scroll pane. list = new JList(listModel); list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); list.setSelectedIndex(0); list.addListSelectionListener(this); list.setVisibleRowCount(5); JScrollPane listScrollPane = new JScrollPane(list); JButton hireButton = new JButton(hireString); HireListener hireListener = new HireListener(hireButton); hireButton.setActionCommand(hireString); hireButton.addActionListener(hireListener); hireButton.setEnabled(false); fireButton = new JButton(fireString); fireButton.setActionCommand(fireString); fireButton.addActionListener(new FireListener()); employeeName = new JTextField(10); employeeName.addActionListener(hireListener); employeeName.getDocument().addDocumentListener(hireListener); String name = listModel.getElementAt(list.getSelectedIndex()).toString(); // Create a panel that uses BoxLayout. JPanel buttonPane = new JPanel(); buttonPane.setLayout(new BoxLayout(buttonPane, BoxLayout.LINE_AXIS)); buttonPane.add(fireButton); buttonPane.add(Box.createHorizontalStrut(5)); buttonPane.add(new JSeparator(SwingConstants.VERTICAL)); buttonPane.add(Box.createHorizontalStrut(5)); buttonPane.add(employeeName); buttonPane.add(hireButton); buttonPane.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5)); add(listScrollPane, BorderLayout.CENTER); add(buttonPane, BorderLayout.PAGE_END); } class FireListener implements ActionListener { public void actionPerformed(ActionEvent e) { // This method can be called only if // there's a valid selection // so go ahead and remove whatever's selected. int index = list.getSelectedIndex(); listModel.remove(index); int size = listModel.getSize(); if (size == 0) { // Nobody's left, disable firing. fireButton.setEnabled(false); } else { // Select an index. if (index == listModel.getSize()) { // removed item in last position index--; } list.setSelectedIndex(index); list.ensureIndexIsVisible(index); } } } // This listener is shared by the text field and the hire button. class HireListener implements ActionListener, DocumentListener { private boolean alreadyEnabled = false; private JButton button; public HireListener(JButton button) { this.button = button; } // Required by ActionListener. public void actionPerformed(ActionEvent e) { String name = employeeName.getText(); // User didn't type in a unique name... if (name.equals("") || alreadyInList(name)) { Toolkit.getDefaultToolkit().beep(); employeeName.requestFocusInWindow(); employeeName.selectAll(); return; } int index = list.getSelectedIndex(); // get selected index if (index == -1) { // no selection, so insert at beginning index = 0; } else { // add after the selected item index++; } listModel.insertElementAt(employeeName.getText(), index); // If we just wanted to add to the end, we'd do this: // listModel.addElement(employeeName.getText()); // Reset the text field. employeeName.requestFocusInWindow(); employeeName.setText(""); // Select the new item and make it visible. list.setSelectedIndex(index); list.ensureIndexIsVisible(index); } // This method tests for string equality. You could certainly // get more sophisticated about the algorithm. For example, // you might want to ignore white space and capitalization. protected boolean alreadyInList(String name) { return listModel.contains(name); } // Required by DocumentListener. public void insertUpdate(DocumentEvent e) { enableButton(); } // Required by DocumentListener. public void removeUpdate(DocumentEvent e) { handleEmptyTextField(e); } // Required by DocumentListener. public void changedUpdate(DocumentEvent e) { if (!handleEmptyTextField(e)) { enableButton(); } } private void enableButton() { if (!alreadyEnabled) { button.setEnabled(true); } } private boolean handleEmptyTextField(DocumentEvent e) { if (e.getDocument().getLength() <= 0) { button.setEnabled(false); alreadyEnabled = false; return true; } return false; } } // This method is required by ListSelectionListener. public void valueChanged(ListSelectionEvent e) { if (e.getValueIsAdjusting() == false) { if (list.getSelectedIndex() == -1) { // No selection, disable fire button. fireButton.setEnabled(false); } else { // Selection, enable the fire button. fireButton.setEnabled(true); } } } /** * Create the GUI and show it. For thread safety, this method should be * invoked from the event-dispatching thread. */ private static void createAndShowGUI() { // Create and set up the window. JFrame frame = new JFrame("ListDemo"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // Create and set up the content pane. JComponent newContentPane = new ListDemo(); newContentPane.setOpaque(true); // content panes must be opaque frame.setContentPane(newContentPane); // Display the window. frame.pack(); frame.setVisible(true); } public static void main(String[] args) { // Schedule a job for the event-dispatching thread: // creating and showing this application's GUI. javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { createAndShowGUI(); } }); } }