JAVA监听器添加的四种方式（自身、外部类、内部类、匿名类）

import javax.swing.*;  
import java.awt.*;  
import java.awt.event.*;  
       
public class ThisClassEvent extends JFrame implements ActionListener{    
    public ThisClassEvent(){        
        setLayout(new FlowLayout());           
        JButton btn=new JButton("ok");
        add(btn);
        btn.addActionListener(this);  
    }    
    public void actionPerformed (ActionEvent e){  
     System.out.println("The OK button is clicked");
    }    
    public static void main(String args[]){
     ThisClassEvent frame = new ThisClassEvent();
        frame.setTitle("自身类作为事件监听器");
        frame.setLocationRelativeTo(null); // Center the frame
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(280, 100);
        frame.setVisible(true);
        new ThisClassEvent();  
    }  
}

import java.awt.*;  
import java.awt.event.*;  
import javax.swing.*;  
      
public class OuterClassEvent extends JFrame{     
    public OuterClassEvent(){  
     setLayout(new FlowLayout());           
        JButton btn=new JButton("ok");
        add(btn);
        OuterClass btListener=new OuterClass();
        btn.addActionListener(btListener);  
    }    
    public static void main(String args[]){  
     OuterClassEvent frame = new OuterClassEvent();
        frame.setTitle("外部类作为事件监听器");
        frame.setLocationRelativeTo(null); // Center the frame
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(280, 100);
        frame.setVisible(true);
        new ThisClassEvent();  
    }  
}     
class OuterClass implements ActionListener{ 
    public void actionPerformed(ActionEvent e){  
     System.out.println("The OK button is clicked");
    }  
}  

import java.awt.*;  
import java.awt.event.*;  
import javax.swing.*;  
      
class InnerClassEvent extends JFrame{   
    public InnerClassEvent(){  
     setLayout(new FlowLayout());           
        JButton btn=new JButton("ok");
        add(btn);
        OuterClass btListener=new OuterClass();
        btn.addActionListener(btListener);  
    }
    class InnerClass implements ActionListener{  
        public void actionPerformed (ActionEvent e){  
         System.out.println("The OK button is clicked");
        }  
    }  
    public static void main(String args[]){  
     InnerClassEvent frame = new InnerClassEvent();
        frame.setTitle("内部类作为事件监听器");
        frame.setLocationRelativeTo(null); // Center the frame
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(280, 100);
        frame.setVisible(true);
        new ThisClassEvent();  
    }  
 
}

import java.awt.*;  
import java.awt.event.*;  
import javax.swing.*;  
         
class AnonymousEvent extends JFrame{   
    public AnonymousEvent(){  
     setLayout(new FlowLayout());           
        JButton btn=new JButton("ok");
        add(btn);     
        btn.addActionListener(  
            new ActionListener(){   //匿名内部类作为参数，new 一个lisenter实际上是创建了一个实现了这个listener的类
                public void actionPerformed(ActionEvent e){  
                 System.out.println("The OK button is clicked");
                }  
            }  
        );   
    }  
    public static void main(String args[]){  
     AnonymousEvent frame = new AnonymousEvent();
        frame.setTitle("匿名内部类作为事件监听器");
        frame.setLocationRelativeTo(null); // Center the frame
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(280, 100);
        frame.setVisible(true);
        new ThisClassEvent();  
    }  
}