控制台程序。
为表示事件的常量使用标识符可以直接启用组件对象的特定事件组。调用组件的enableEvent()方法，并把想要启用事件的标识符传送为参数，但这只在不使用监视器的情况下有效。注册监听器会自动启用监听器想要监听的事件，所以不需要调用enableEvent()方法。只有当希望对象能处理自己的某些事件时，才调用enableEvent()方法，但使用监听器可以达到相同的效果。
使用监听器对象是处理事件的首选方式，因为更容易直接启用对象的事件，代码也更简洁。
// Main window for the Sketcher application
import javax.swing.*;
import static java.awt.event.InputEvent.*; // For modifier constants
import java.awt.event.WindowEvent; @SuppressWarnings("serial")
public class SketcherFrame extends JFrame {
// Constructor
public SketcherFrame(String title) {
setTitle(title); // Set the window title setJMenuBar(menuBar); // Add the menu bar to the window JMenu fileMenu = new JMenu("File"); // Create File menu
JMenu elementMenu = new JMenu("Elements"); // Create Elements menu
fileMenu.setMnemonic('F'); // Create shortcut
elementMenu.setMnemonic('E'); // Create shortcut // Construct the file drop-down menu
newItem = fileMenu.add("New"); // Add New item
openItem = fileMenu.add("Open"); // Add Open item
closeItem = fileMenu.add("Close"); // Add Close item
fileMenu.addSeparator(); // Add separator
saveItem = fileMenu.add("Save"); // Add Save item
saveAsItem = fileMenu.add("Save As..."); // Add Save As item
fileMenu.addSeparator(); // Add separator
printItem = fileMenu.add("Print"); // Add Print item // Add File menu accelerators
newItem.setAccelerator(KeyStroke.getKeyStroke('N',CTRL_DOWN_MASK ));
openItem.setAccelerator(KeyStroke.getKeyStroke('O', CTRL_DOWN_MASK));
saveItem.setAccelerator(KeyStroke.getKeyStroke('S', CTRL_DOWN_MASK));
printItem.setAccelerator(KeyStroke.getKeyStroke('P', CTRL_DOWN_MASK)); // Construct the Element drop-down menu
elementMenu.add(lineItem = new JRadioButtonMenuItem("Line", true));
elementMenu.add(rectangleItem = new JRadioButtonMenuItem("Rectangle", false));
elementMenu.add(circleItem = new JRadioButtonMenuItem("Circle", false));
elementMenu.add(curveItem = new JRadioButtonMenuItem("Curve", false));
ButtonGroup types = new ButtonGroup();
types.add(lineItem);
types.add(rectangleItem);
types.add(circleItem);
types.add(curveItem); // Add element type accelerators
lineItem.setAccelerator(KeyStroke.getKeyStroke('L', CTRL_DOWN_MASK));
rectangleItem.setAccelerator(KeyStroke.getKeyStroke('E', CTRL_DOWN_MASK));
circleItem.setAccelerator(KeyStroke.getKeyStroke('I', CTRL_DOWN_MASK));
curveItem.setAccelerator(KeyStroke.getKeyStroke('V', CTRL_DOWN_MASK)); elementMenu.addSeparator();
JMenu colorMenu = new JMenu("Color"); // Color submenu
elementMenu.add(colorMenu); // Add the submenu
colorMenu.add(redItem = new JCheckBoxMenuItem("Red", false));
colorMenu.add(yellowItem = new JCheckBoxMenuItem("Yellow", false));
colorMenu.add(greenItem = new JCheckBoxMenuItem("Green", false));
colorMenu.add(blueItem = new JCheckBoxMenuItem("Blue", true)); // Add element color accelerators
redItem.setAccelerator(KeyStroke.getKeyStroke('R', CTRL_DOWN_MASK));
yellowItem.setAccelerator(KeyStroke.getKeyStroke('Y', CTRL_DOWN_MASK));
greenItem.setAccelerator(KeyStroke.getKeyStroke('G', CTRL_DOWN_MASK));
blueItem.setAccelerator(KeyStroke.getKeyStroke('B', CTRL_DOWN_MASK)); menuBar.add(fileMenu); // Add the file menu
menuBar.add(elementMenu); // Add the element menu
enableEvents(WINDOW_EVENT_MASK); // Enable window events
} // Handle window events
protected void processWindowEvent(WindowEvent e) {
if (e.getID() == WindowEvent.WINDOW_CLOSING) {
dispose(); // Release resources
System.exit(0); // Exit the program
}
super.processWindowEvent(e); // Pass on the event
} private JMenuBar menuBar = new JMenuBar(); // Window menu bar // File menu items
private JMenuItem newItem, openItem, closeItem,
saveItem, saveAsItem, printItem; // Element menu items
private JRadioButtonMenuItem lineItem, rectangleItem, circleItem, // Types
curveItem, textItem;
private JCheckBoxMenuItem redItem, yellowItem, // Colors
greenItem, blueItem ;
}
// Sketching application
import javax.swing.*;
import java.awt.*; import javax.swing.SwingUtilities; public class Sketcher {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createWindow();
}
});
} public static void createWindow(){
window = new SketcherFrame("Sketcher"); // Create the app window
Toolkit theKit = window.getToolkit(); // Get the window toolkit
Dimension wndSize = theKit.getScreenSize(); // Get screen size // Set the position to screen center & size to half screen size
window.setSize(wndSize.width/2, wndSize.height/2); // Set window size
window.setLocationRelativeTo(null); // Center window
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); window.setVisible(true);
} private static SketcherFrame window; // The application window
}