Java基础之处理事件——使窗口处理自己的事件（Skethcer 1 handing its own closing event）
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。
1 // Main window for the Sketcher application 2 import javax.swing.*; 3 import static java.awt.event.InputEvent.*; // For modifier constants 4 import java.awt.event.WindowEvent; 5 6 @SuppressWarnings("serial") 7 public class SketcherFrame extends JFrame { 8 // Constructor 9 public SketcherFrame(String title) { 10 setTitle(title); // Set the window title 11 12 setJMenuBar(menuBar); // Add the menu bar to the window 13 14 JMenu fileMenu = new JMenu("File"); // Create File menu 15 JMenu elementMenu = new JMenu("Elements"); // Create Elements menu 16 fileMenu.setMnemonic('F'); // Create shortcut 17 elementMenu.setMnemonic('E'); // Create shortcut 18 19 // Construct the file drop-down menu 20 newItem = fileMenu.add("New"); // Add New item 21 openItem = fileMenu.add("Open"); // Add Open item 22 closeItem = fileMenu.add("Close"); // Add Close item 23 fileMenu.addSeparator(); // Add separator 24 saveItem = fileMenu.add("Save"); // Add Save item 25 saveAsItem = fileMenu.add("Save As..."); // Add Save As item 26 fileMenu.addSeparator(); // Add separator 27 printItem = fileMenu.add("Print"); // Add Print item 28 29 // Add File menu accelerators 30 newItem.setAccelerator(KeyStroke.getKeyStroke('N',CTRL_DOWN_MASK )); 31 openItem.setAccelerator(KeyStroke.getKeyStroke('O', CTRL_DOWN_MASK)); 32 saveItem.setAccelerator(KeyStroke.getKeyStroke('S', CTRL_DOWN_MASK)); 33 printItem.setAccelerator(KeyStroke.getKeyStroke('P', CTRL_DOWN_MASK)); 34 35 // Construct the Element drop-down menu 36 elementMenu.add(lineItem = new JRadioButtonMenuItem("Line", true)); 37 elementMenu.add(rectangleItem = new JRadioButtonMenuItem("Rectangle", false)); 38 elementMenu.add(circleItem = new JRadioButtonMenuItem("Circle", false)); 39 elementMenu.add(curveItem = new JRadioButtonMenuItem("Curve", false)); 40 ButtonGroup types = new ButtonGroup(); 41 types.add(lineItem); 42 types.add(rectangleItem); 43 types.add(circleItem); 44 types.add(curveItem); 45 46 // Add element type accelerators 47 lineItem.setAccelerator(KeyStroke.getKeyStroke('L', CTRL_DOWN_MASK)); 48 rectangleItem.setAccelerator(KeyStroke.getKeyStroke('E', CTRL_DOWN_MASK)); 49 circleItem.setAccelerator(KeyStroke.getKeyStroke('I', CTRL_DOWN_MASK)); 50 curveItem.setAccelerator(KeyStroke.getKeyStroke('V', CTRL_DOWN_MASK)); 51 52 elementMenu.addSeparator(); 53 JMenu colorMenu = new JMenu("Color"); // Color submenu 54 elementMenu.add(colorMenu); // Add the submenu 55 colorMenu.add(redItem = new JCheckBoxMenuItem("Red", false)); 56 colorMenu.add(yellowItem = new JCheckBoxMenuItem("Yellow", false)); 57 colorMenu.add(greenItem = new JCheckBoxMenuItem("Green", false)); 58 colorMenu.add(blueItem = new JCheckBoxMenuItem("Blue", true)); 59 60 // Add element color accelerators 61 redItem.setAccelerator(KeyStroke.getKeyStroke('R', CTRL_DOWN_MASK)); 62 yellowItem.setAccelerator(KeyStroke.getKeyStroke('Y', CTRL_DOWN_MASK)); 63 greenItem.setAccelerator(KeyStroke.getKeyStroke('G', CTRL_DOWN_MASK)); 64 blueItem.setAccelerator(KeyStroke.getKeyStroke('B', CTRL_DOWN_MASK)); 65 66 menuBar.add(fileMenu); // Add the file menu 67 menuBar.add(elementMenu); // Add the element menu 68 enableEvents(WINDOW_EVENT_MASK); // Enable window events 69 } 70 71 // Handle window events 72 protected void processWindowEvent(WindowEvent e) { 73 if (e.getID() == WindowEvent.WINDOW_CLOSING) { 74 dispose(); // Release resources 75 System.exit(0); // Exit the program 76 } 77 super.processWindowEvent(e); // Pass on the event 78 } 79 80 private JMenuBar menuBar = new JMenuBar(); // Window menu bar 81 82 // File menu items 83 private JMenuItem newItem, openItem, closeItem, 84 saveItem, saveAsItem, printItem; 85 86 // Element menu items 87 private JRadioButtonMenuItem lineItem, rectangleItem, circleItem, // Types 88 curveItem, textItem; 89 private JCheckBoxMenuItem redItem, yellowItem, // Colors 90 greenItem, blueItem ; 91 }
1 // Sketching application 2 import javax.swing.*; 3 import java.awt.*; 4 5 import javax.swing.SwingUtilities; 6 7 public class Sketcher { 8 public static void main(String[] args) { 9 SwingUtilities.invokeLater(new Runnable() { 10 public void run() { 11 createWindow(); 12 } 13 }); 14 } 15 16 public static void createWindow(){ 17 window = new SketcherFrame("Sketcher"); // Create the app window 18 Toolkit theKit = window.getToolkit(); // Get the window toolkit 19 Dimension wndSize = theKit.getScreenSize(); // Get screen size 20 21 // Set the position to screen center & size to half screen size 22 window.setSize(wndSize.width/2, wndSize.height/2); // Set window size 23 window.setLocationRelativeTo(null); // Center window 24 window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 25 26 window.setVisible(true); 27 } 28 29 private static SketcherFrame window; // The application window 30 }