Java 内部类和匿名类 实现JButton动作 ActionListener类

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

 public class ControlCircle2 extends JFrame {
     private JButton jbtEnlarge=new JButton("Enlarge");
     private JButton jbtShrink=new JButton("Shrink");
     private CirclePanel canvas=new CirclePanel();

     public ControlCircle2(){
         JPanel panel=new JPanel();
         panel.add(jbtEnlarge);
         panel.add(jbtShrink);
         this.add(canvas,BorderLayout.CENTER);
         this.add(panel, BorderLayout.SOUTH);

         jbtEnlarge.addActionListener(new EnlargeListener());
         jbtShrink.addActionListener(new ShrinkListener());
     }

     public static void main(String[] args) {
         // TODO Auto-generated method stub
         ControlCircle2 frame=new ControlCircle2();
         frame.setTitle("ControlCircle2");
         frame.setSize(200,200);
         frame.setLocationRelativeTo(null);
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         frame.setVisible(true);

     }
     class ShrinkListener implements ActionListener{
         @Override
         public void actionPerformed(ActionEvent e) {
             // TODO Auto-generated method stub
             canvas.shrink();
         }
     }
     class EnlargeListener implements ActionListener{
         @Override
         public void actionPerformed(ActionEvent e) {
             // TODO Auto-generated method stub
             canvas.enlarge();
         }
     }

 }
 class CirclePanel extends JPanel {
     private int radius=5;
     public void enlarge(){
         radius++;
         repaint();
     }
     public void shrink(){
         if(radius>=1){
         radius--;
         repaint();}
         else
             JOptionPane.showMessageDialog(null, "Radius can not less than 1.");
     }
     protected void paintComponent(Graphics g){
         super.paintComponent(g);
         g.drawOval(getWidth()/2-radius, getHeight()/2,
                 2*radius, 2*radius);
     }

 }

为了让actionPerformed方法可以访问到canvas变量，将EnlargeListener定义为ControlCircle2类的内部类。

匿名内部类是没有名字的内部类，它一步完成定义内部类和创建一个该类的实例。

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

 public class AnonymousListenerDemo extends JFrame {
     public AnonymousListenerDemo(){
         JButton jbtNew=new JButton("New");
         JButton jbtOpen=new JButton("Open");
         JButton jbtSave=new JButton("Save");
         JButton jbtPrint=new JButton("Print");

         JPanel panel=new JPanel();
         panel.add(jbtNew);
         panel.add(jbtOpen);
         panel.add(jbtSave);
         panel.add(jbtPrint);

         add(panel);

         jbtNew.addActionListener(new ActionListener() {
             public void actionPerformed(ActionEvent e){
                 System.out.println("Process New");
             }
         });//匿名内部类

         jbtOpen.addActionListener(new ActionListener(){
             public void actionPerformed(ActionEvent e){
                 System.out.println("Process Open");
             }
         });

         jbtSave.addActionListener(new ActionListener(){
             public void actionPerformed(ActionEvent e){
                 System.out.println("Process Save");
             }
         });

         jbtPrint.addActionListener(new ActionListener(){
             public void actionPerformed(ActionEvent e){
                 System.out.println("Process Print");
             }
         });
     }

     public static void main(String[] args) {
         // TODO Auto-generated method stub
         AnonymousListenerDemo frame=new AnonymousListenerDemo();
         frame.setTitle("AnonymousListenerDemo");
         frame.pack();//程序没有使用setSize方法来设置框架的大小，而是使用pack方法，可以根据组件的大小来自动调整框架的大小。
         frame.setLocationRelativeTo(null);
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         frame.setVisible(true);

     }

 }

还可以只使用一个actionListener，通过获取ActionEvent的类别，来触发相应的动作。

 class ButtonListener implements ActionListener {
         @Override
         public void actionPerformed(ActionEvent e) {
             // TODO Auto-generated method stub
             if(e.getSource()==jbtNew)//使用getSource方法，获得事件的对象，然后使用对应的动作。
                 {System.out.println("Process New");
                 JOptionPane.showMessageDialog(null, "Process New");}
             else if(e.getSource()==jbtOpen)
                 {System.out.println("Process Open");
                 JOptionPane.showMessageDialog(null, "Process Open");}
             else if(e.getSource()==jbtSave)
                 {System.out.println("Process Save");
                 JOptionPane.showMessageDialog(null, "Process Save");}
             else if(e.getSource()==jbtPrint)
                 {System.out.println("Process Print");
                 JOptionPane.showMessageDialog(null, "Process Print");}
         }
     }