Java基础之处理事件——applet中语义事件的处理（Lottery 1）

控制台程序。

语义事件与程序GUI上的组件操作有关。例如，如果选择菜单项或单击按钮，就会生成语义事件。

对组件执行操作时，例如选择菜单项或单击按钮，就会生成ActionEvent事件。在选择或取消选择某个组件时，会生成ItemEvent事件。在调整可调整的对象(如滚动条）时，就生成AdjustmentEvent事件。

上面的每一种语义事件类型都定义了相应的监听器接口，这些接口都只声明了一个方法：

1、ActionListener定义了actionPerformed(ActionEvent e)方法。

2、ItemListener定义了itemStateChanged(ItemEvent e)方法。

3、AdjustmentListener定义了adjustmentValueChanged(AdjustmentEvent e)方法。

 // Applet to generate lottery entries
 import javax.swing.*;
 import java.awt.*;
 import java.awt.event.*;
 import java.util.Random;                                               // For random number generator

 @SuppressWarnings("serial")
 public class Lottery extends JApplet {
   // Generate NUMBER_COUNT random selections from the VALUES array
   private static int[] getNumbers() {
     int[] numbers = new int[NUMBER_COUNT];                             // Store for the numbers to be returned
     int candidate = 0;                                                 // Stores a candidate selection
     for(int i = 0; i < NUMBER_COUNT; ++i) {                            // Loop to find the selections

       search:
       // Loop to find a new selection different from any found so far
       while(true) {
         candidate = VALUES[choice.nextInt(VALUES.length)];
         for(int j = 0 ; j < i ; ++j) {                                 // Check against existing selections
           if(candidate==numbers[j]) {                                  // If it is the same
             continue search;                                           // get another random selection
           }
         }
         numbers[i] = candidate;                                        // Store the selection in numbers array
         break;                                                         // and go to find the next
       }
     }
     return numbers;                                                    // Return the selections
   }

   // Initialize the applet
   @Override
   public void init() {
     SwingUtilities.invokeLater(                                        // Create interface components
       new Runnable() {                                                 // on the event dispatching thread
         public void run() {
           createGUI();
         }
     });
   }

   // Create User Interface for applet
   public void createGUI() {
     // Set up the selection buttons
     Container content = getContentPane();
     content.setLayout(new GridLayout(0,1));                            // Set the layout for the applet

     // Set up the panel to hold the lucky number buttons
     JPanel buttonPane = new JPanel();                                  // Add the pane containing numbers

     // Let's have a fancy panel border
     buttonPane.setBorder(BorderFactory.createTitledBorder(
                          BorderFactory.createEtchedBorder(Color.cyan,
                                                           Color.blue),
                                                           "Every One a Winner!"));

     int[] choices = getNumbers();                                      // Get initial set of numbers
     for(int i = 0 ; i < NUMBER_COUNT ; ++i) {
      luckyNumbers[i] = new Selection(choices[i]);
      luckyNumbers[i].addActionListener(luckyNumbers[i]);               // Button is it's own listener
      buttonPane.add(luckyNumbers[i]);
     }
     content.add(buttonPane);

     // Add the pane containing control buttons
    JPanel controlPane = new JPanel(new FlowLayout(FlowLayout.CENTER, 5, 10));

     // Add the two control buttons
     JButton button;                                                    // A button variable
     Dimension buttonSize = new Dimension(100,20);                      // Button size

     controlPane.add(button = new JButton("Lucky Numbers!"));
     button.setBorder(BorderFactory.createRaisedBevelBorder());
     button.addActionListener(new HandleControlButton(PICK_LUCKY_NUMBERS));
     button.setPreferredSize(buttonSize);

     controlPane.add(button = new JButton("Color"));
     button.setBorder(BorderFactory.createRaisedBevelBorder());
     button.addActionListener(new HandleControlButton(COLOR));
     button.setPreferredSize(buttonSize);

     content.add(controlPane);
   }

   // Class defining custom buttons showing lottery selection
   private class Selection extends JButton implements ActionListener {
     // Constructor
     public Selection(int value) {
       super(Integer.toString(value));                                  // Call base constructor and set the label
       this.value = value;                                              // Save the value
       setBackground(startColor);
       setBorder(BorderFactory.createRaisedBevelBorder());              // Add button border
       setPreferredSize(new Dimension(80,20));
     }

     // Handle selection button event
     public void actionPerformed(ActionEvent e) {
       // Change this selection to a new selection
       int candidate = 0;
       while(true) {                                                    // Loop to find a different selection
         candidate = VALUES[choice.nextInt(VALUES.length)];
         if(!isCurrentSelection(candidate)) {                           // If it is different
           break;                                                       // end the loop
         }
       }
       setValue(candidate);                                             // We have one so set the button value
     }
     // Set the value for the selection
     public void setValue(int value) {
       setText(Integer.toString(value));                                // Set value as the button label
       this.value = value;                                              // Save the value
     }

     // Check the value for the selection
     boolean hasValue(int possible) {
       return value==possible;                                          // Return true if equals current value
     }

     // Check the current choices
     boolean isCurrentSelection(int possible) {
       for(int i = 0 ; i < NUMBER_COUNT ; ++i) {                        // For each button
         if(luckyNumbers[i].hasValue(possible)) {                       // check against possible
           return true;                                                 // Return true for any =
         }
       }
       return false;                                                    // Otherwise return false
     }

     private int value;                                                 // Value for the selection button
   }

   // Class defining a handler for a control button
   private class HandleControlButton implements ActionListener {
     // Constructor
     public HandleControlButton(int buttonID) {
       this.buttonID = buttonID;                                        // Store the button ID
     }

     // Handle button click
     public void actionPerformed(ActionEvent e) {
       switch(buttonID) {
         case PICK_LUCKY_NUMBERS:
           int[] numbers = getNumbers();                                // Get maxCount random numbers
           for(int i = 0; i < NUMBER_COUNT; ++i) {
             luckyNumbers[i].setValue(numbers[i]);                      // Set the button VALUES
           }
           break;
         case COLOR:
           Color color = new Color(
                 flipColor.getRGB()^luckyNumbers[0].getBackground().getRGB());
           for(int i = 0; i < NUMBER_COUNT; ++i)
             luckyNumbers[i].setBackground(color);                      // Set the button colors
           break;
       }
     }

     private int buttonID;
   }

   final static int NUMBER_COUNT = 6;                                   // Number of lucky numbers
   final static int MIN_VALUE = 1;                                      // Minimum in range
   final static int MAX_VALUE = 49;                                     // Maximum in range
   final static int[] VALUES = new int[MAX_VALUE-MIN_VALUE+1];          // Array of possible VALUES
   static {                                                             // Initialize array
     for(int i = 0 ; i < VALUES.length ; ++i)
       VALUES[i] = i + MIN_VALUE;
   }

   // An array of custom buttons for the selected numbers
   private Selection[] luckyNumbers = new Selection[NUMBER_COUNT];
   final public static int PICK_LUCKY_NUMBERS = 1;                      // Select button ID
   final public static int COLOR = 2;                                   // Color button ID

   // swap colors
   Color flipColor = new Color(Color.YELLOW.getRGB()^Color.RED.getRGB());

   Color startColor = Color.YELLOW;                                     // start color

   private static Random choice = new Random();                         // Random number generator
 }

还需要一个HTML文件：

 <html>
     <head>
     </head>
     <body bgcolor="000000">
         <center>
             <applet
                 code    = "Lottery.class"
                 width    = "300"
                 height    = "200"
                 >
             </applet>
         </center>
     </body>
 </html>