java - 尝试将 ActionListener 添加到 JButtons

Question

我不知道如何将 Actionlisteners 添加到 JButton 中，非常感谢任何帮助。

public class Translator extends JPanel implements MouseListener, ActionListener {       

    private JButton french = new JButton();
    private JButton german = new JButton();
    private JButton irish = new JButton();

    public Translator(){
        french = new JButton("French");
        german = new JButton("German");
        irish = new JButton("Irish");           
        setLayout(new GridLayout(2,1));         
        buttonPanel.setLayout(new GridLayout(1,3));
        buttonPanel.add(french);
        buttonPanel.add(german);
        buttonPanel.add(irish);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        // TODO Auto-generated method stub
    }

    @Override
    public void mouseClicked(MouseEvent e) {
        // TODO Auto-generated method stub
    }

    @Override
    public void mouseEntered(MouseEvent e) {
        // TODO Auto-generated method stub
    }
}

Answer 1

有很多方法可以将 ActionListener 添加到给定的 JComponent(支持它的使用)。我在代码片段中添加了一些注释，以帮助更好地解释它们，并在注释中添加了一些链接以供将来引用。

1.) 如果类实现了ActionListener接口(interface)，即类本身包含actionPerformed(...)方法，那么可以通过这种方式做到这一点:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Skeleton implements ActionListener {   

    private JFrame frame;
    private JPanel contentPane;
    private JButton button;

    private void displayGUI() {
        frame = new JFrame("Skeleton");
        /*
         * EXIT_ON_CLOSE is same as putting System.exit(0),
         * which in some sense, doesnot allows one's
         * application to terminate graciously.
         */ 
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        contentPane = new JPanel();
        button = new JButton("This is a button.");
        /*
         * This is one way of attaching an ActionListener
         * to the JButton, but the main disadvantage of
         * this approach is, it breaks encapsulation,
         * as you can see the public method, actionPerformed(),
         * is lying free to be accessed by any code outside
         * the scope of the class
         */
        button.addActionListener(this);

        contentPane.add(button);

        frame.setContentPane(contentPane);        
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);                                
    }

    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                new Skeleton().displayGUI();
            }
        };
        EventQueue.invokeLater(runnable);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        JOptionPane.showMessageDialog(frame, "BINGO!",
            "Information: ", JOptionPane.INFORMATION_MESSAGE);
    }    
}

2.) 如果不想创建不必要的 class 文件。然后可以使用使用 EventHandler 的这种方法:

import java.awt.*;
import java.awt.event.*;
import java.beans.EventHandler;
import javax.swing.*;

public class Example1 { 

    private JFrame frame;
    private JPanel contentPane;
    private JButton button;

    private void displayGUI() {
        frame = new JFrame("Skeleton");
        /*
         * EXIT_ON_CLOSE is same as putting System.exit(0),
         * which in some sense, doesnot allows one's
         * application to terminate graciously.
         */ 
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        contentPane = new JPanel();
        button = new JButton("This is a button.");
        /*
         * This is another way of attaching 
         * an ActionListener to the JButton,
         * the main advantage of this approach
         * is, that one does not have to create
         * a new class to handle events
         * More info regarding the use of this 
         * approach, can be found on this link : 
         * http://docs.oracle.com/javase/tutorial/uiswing/events/generalrules.html
         */
        button.addActionListener((ActionListener)
                EventHandler.create(ActionListener.class
                        , Example1.this, "buttonAction", ""));

        contentPane.add(button);

        frame.setContentPane(contentPane);        
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);                                
    }

    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                new Example1().displayGUI();
            }
        };
        EventQueue.invokeLater(runnable);
    }

    public void buttonAction(ActionEvent e) {
        JOptionPane.showMessageDialog(frame, "BINGO!",
            "Information: ", JOptionPane.INFORMATION_MESSAGE);
    }    
}

3.) 如果一个人更关心封装的概念，那么这种方法是有益的:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Example2 { 

    private JFrame frame;
    private JPanel contentPane;
    private JButton button;

    private ActionListener buttonActions = 
                            new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent ae) {
            JOptionPane.showMessageDialog(frame, "BINGO!",
                "Information: ", JOptionPane.INFORMATION_MESSAGE);
        }
    };

    private void displayGUI() {
        frame = new JFrame("Skeleton");
        /*
         * EXIT_ON_CLOSE is same as putting System.exit(0),
         * which in some sense, doesnot allows one's
         * application to terminate graciously.
         */ 
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        contentPane = new JPanel();
        button = new JButton("This is a button.");
        /*
         * This is another way of attaching 
         * an ActionListener to the JButton,
         * the main advantage of this approach
         * is, it adheres to encapsulation.
         */
        button.addActionListener(buttonActions);

        contentPane.add(button);

        frame.setContentPane(contentPane);        
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);                                
    }

    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                new Example2().displayGUI();
            }
        };
        EventQueue.invokeLater(runnable);
    }    
}

4.) 如果更倾向于创建匿名类，则可以使用这种方法:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Example3 { 

    private JFrame frame;
    private JPanel contentPane;
    private JButton button;

    private void displayGUI() {
        frame = new JFrame("Skeleton");
        /*
         * EXIT_ON_CLOSE is same as putting System.exit(0),
         * which in some sense, doesnot allows one's
         * application to terminate graciously.
         */ 
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        contentPane = new JPanel();
        button = new JButton("This is a button.");
        /* 
         * This is the fourth way of attaching  
         * an ActionListener to the JButton, 
         * the main advantage of this approach 
         * is, it adheres to encapsulation, the 
         * public method remains hidden
         * inside the Anonymous Class
         * More info can be found on this link : 
         * http://docs.oracle.com/javase/tutorial/java/javaOO/anonymousclasses.html
         * The main disadvantage of this approach is
         * that it doesnot gives you the privilege
         * of separation of concerns, which can
         * be done using the fifth approach,
         * which is MVC - Pattern (Model-View-Controller)
         * and moreover, it creates a hell lot of classes, in 
         * your project, which can lead to extra overhead
         */
        button.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent ae) {
                JOptionPane.showMessageDialog(frame, "BINGO!",
                    "Information: ", JOptionPane.INFORMATION_MESSAGE);
            }
        });

        contentPane.add(button);

        frame.setContentPane(contentPane);        
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);                                
    }

    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                new Example3().displayGUI();
            }
        };
        EventQueue.invokeLater(runnable);
    }    
}

编辑:

5.) 这种方法包括使用 Action 而不是 ActionListener。这将用于在各种 JComponent 之间共享相同的功能，从而实现代码的可重用性

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Example4 { 

    private JFrame frame;
    private JPanel contentPane;
    private JMenuItem showMenuItem;
    private JButton button;

    private Action myActions;

    /*
     * This approach is basically used, when
     * one wants to share the same functionality
     * of different JComponents among each other,
     * without writing redundant codes for each
     * one of those components. Here JMenuItem
     * and JButton are both using the same 
     * functionality, to perform the same task.
     * More info can be found on this link:
     * http://docs.oracle.com/javase/tutorial/uiswing/misc/action.html
     */
    private class MyActions extends AbstractAction {
        public MyActions(String title, String desc) {
            super(title);
            putValue(SHORT_DESCRIPTION, desc);
        }

        @Override
        public void actionPerformed(ActionEvent ae) {
            JOptionPane.showMessageDialog(frame, "BINGO!",
                    "Information: ", JOptionPane.INFORMATION_MESSAGE);
        }
    }

    private void displayGUI() {
        frame = new JFrame("Skeleton");
        /*
         * EXIT_ON_CLOSE is same as putting System.exit(0),
         * which in some sense, doesnot allows one's
         * application to terminate graciously.
         */ 
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        contentPane = new JPanel();
        button = new JButton("This is a button.");

        myActions = new MyActions("Show", "A small description");
        button.setAction(myActions);

        contentPane.add(button);

        frame.setJMenuBar(getJMenuBar());
        frame.setContentPane(contentPane);        
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);                                
    }

    private JMenuBar getJMenuBar() {
        JMenuBar menuBar = new JMenuBar();
        JMenu fileMenu = new JMenu("File");
        showMenuItem = new JMenuItem(myActions);
        fileMenu.add(showMenuItem);

        menuBar.add(fileMenu);

        return menuBar;
    }

    public static void main(String[] args) {
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                new Example4().displayGUI();
            }
        };
        EventQueue.invokeLater(runnable);
    }    
}