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. */ /* * FocusEventDemo.java * */ import java.awt.Container; import java.awt.Dimension; import java.awt.GridBagConstraints; import java.awt.GridBagLayout; import java.awt.Insets; import java.awt.event.FocusEvent; import java.awt.event.FocusListener; import java.util.Vector; import javax.swing.BorderFactory; import javax.swing.JButton; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JList; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JTextArea; import javax.swing.JTextField; import javax.swing.UIManager; import javax.swing.UnsupportedLookAndFeelException; public class FocusEventDemo extends JFrame implements FocusListener { final static String newline = "\n"; JTextArea display; public FocusEventDemo(String name) { super(name); } public void addComponentsToPane(final Container pane) { GridBagLayout gridbag = new GridBagLayout(); pane.setLayout(gridbag); GridBagConstraints c = new GridBagConstraints(); c.fill = GridBagConstraints.HORIZONTAL; c.weightx = 1.0; // Make column as wide as possible. JTextField textField = new JTextField("A TextField"); textField.setMargin(new Insets(0, 2, 0, 2)); textField.addFocusListener(this); gridbag.setConstraints(textField, c); add(textField); c.weightx = 0.1; // Widen every other column a bit, when possible. c.fill = GridBagConstraints.NONE; JLabel label = new JLabel("A Label"); label.setBorder(BorderFactory.createEmptyBorder(0, 5, 0, 5)); label.addFocusListener(this); gridbag.setConstraints(label, c); add(label); String comboPrefix = "ComboBox Item #"; final int numItems = 15; Vector<String> vector = new Vector<String>(numItems); for (int i = 0; i < numItems; i++) { vector.addElement(comboPrefix + i); } JComboBox comboBox = new JComboBox(vector); comboBox.addFocusListener(this); gridbag.setConstraints(comboBox, c); add(comboBox); c.gridwidth = GridBagConstraints.REMAINDER; JButton button = new JButton("A Button"); button.addFocusListener(this); gridbag.setConstraints(button, c); add(button); c.weightx = 0.0; c.weighty = 0.1; c.fill = GridBagConstraints.BOTH; String listPrefix = "List Item #"; Vector<String> listVector = new Vector<String>(numItems); for (int i = 0; i < numItems; i++) { listVector.addElement(listPrefix + i); } JList list = new JList(listVector); list.setSelectedIndex(1); // It's easier to see the focus change // if an item is selected. list.addFocusListener(this); JScrollPane listScrollPane = new JScrollPane(list); gridbag.setConstraints(listScrollPane, c); add(listScrollPane); c.weighty = 1.0; // Make this row as tall as possible. c.gridheight = GridBagConstraints.REMAINDER; // Set up the area that reports focus-gained and focus-lost events. display = new JTextArea(); display.setEditable(false); // The setRequestFocusEnabled method prevents a // component from being clickable, but it can still // get the focus through the keyboard - this ensures // user accessibility. display.setRequestFocusEnabled(false); display.addFocusListener(this); JScrollPane displayScrollPane = new JScrollPane(display); gridbag.setConstraints(displayScrollPane, c); add(displayScrollPane); setPreferredSize(new Dimension(450, 450)); ((JPanel) pane).setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20)); } public void focusGained(FocusEvent e) { displayMessage("Focus gained", e); } public void focusLost(FocusEvent e) { displayMessage("Focus lost", e); } void displayMessage(String prefix, FocusEvent e) { display.append(prefix + (e.isTemporary() ? " (temporary):" : ":") + e.getComponent().getClass().getName() + "; Opposite component: " + (e.getOppositeComponent() != null ? e.getOppositeComponent().getClass().getName() : "null") + newline); display.setCaretPosition(display.getDocument().getLength()); } /** * Create the GUI and show it. For thread safety, this method should be * invoked from the event dispatch thread. */ private static void createAndShowGUI() { // Create and set up the window. FocusEventDemo frame = new FocusEventDemo("FocusEventDemo"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // Set up the content pane. frame.addComponentsToPane(frame.getContentPane()); // Display the window. frame.pack(); frame.setVisible(true); } public static void main(String[] args) { /* Use an appropriate Look and Feel */ try { // UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel"); UIManager.setLookAndFeel("javax.swing.plaf.metal.MetalLookAndFeel"); } catch (UnsupportedLookAndFeelException ex) { ex.printStackTrace(); } catch (IllegalAccessException ex) { ex.printStackTrace(); } catch (InstantiationException ex) { ex.printStackTrace(); } catch (ClassNotFoundException ex) { ex.printStackTrace(); } /* Turn off metal's use of bold fonts */ UIManager.put("swing.boldMetal", Boolean.FALSE); // Schedule a job for the event dispatch thread: // creating and showing this application's GUI. javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { createAndShowGUI(); } }); } }