Java基础之处理事件——选项按钮的鼠标监听器（Lottery 2 with mouse listener）

控制台程序。

定义监听器类有许多方式。下面把监听器类定义为单独的类MouseHandler:

// Mouse event handler for a selection button
import java.awt.Cursor;
import java.awt.event.*;

public class MouseHandler extends MouseAdapter {
Cursor handCursor = new Cursor(Cursor.HAND_CURSOR);
Cursor defaultCursor = new Cursor(Cursor.DEFAULT_CURSOR);

// Handle mouse entering the selection button
@Override
public void mouseEntered(MouseEvent e) {
e.getComponent().setCursor(handCursor);                            // Switch to hand cursor
}
// Handle mouse exiting the selection button
@Override
public void mouseExited(MouseEvent e) {
e.getComponent().setCursor(defaultCursor);                         // Change to default cursor
}
}

然后修改createGUI()方法中的循环，为applet添加鼠标监听器即可：

// 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
MouseHandler mouseHandler = new MouseHandler();                    // Create the listener
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
luckyNumbers[i].addMouseListener(mouseHandler);
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
}

Html文件和上一个例子一样。

对于鼠标是动作源的任何组件来说，都可以应用上述技巧。