java匿名类监听器

监听器类是特意为创建一个GUI组件而设计的监听器对象.监听器类是不被其他应用程序所共享的.正确的做法是将它作为一个内部类定义在框架类中.

可以使用匿名内部类简化内部类监听器.匿名内部类是没有名字的内部类.

例如

     public ControlCircle(){

          jbtEnlage.addActionListener(

               new EnlargeListener());

     }

     class EnlargeListener implements ActionListener{

           public void actionPerformed(ActionEvent e)

           {

                canvas.enlarge();

           }    

     }

     可以替换为

     public ControlCircle(){

          jbtEnlarge.addActionListener(

          new AciotnListener(){

               public void actionPerformed(AciotnEvent e){

                    canvas.enlarge();

               }

          }

          );

     }

     匿名内部类的语法如下：

     new SuperClassName/InterfaceName(){

          //

          //

     }

匿名内部类必须总是扩展父类或实现接口，但是不能有显式的extends或implements语句

匿名内部类必须事先父类或者接口中的所有抽象方法

匿名内部类总是使用父类的无参构造方法来创建实例

import javax.swing.*;

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(jbtPrint);

              panel.add(jbtSave);

              panel.add(jbtOpen);

              panel.add(jbtNew);

              

              add(panel);

              

              jbtNew.addActionListener(

                            new ActionListener(){

                                   public void actionPerformed(ActionEvent e){

                                         System. out.println("Process new" );

                                  }

                           }

              );

              

              jbtOpen.addActionListener(

                            new ActionListener(){

                                   public void actionPerformed(ActionEvent e){

                                         System. out.println("Process open" );

                                  }

                           }

              );

              

              jbtPrint.addActionListener(

                            new ActionListener(){

                                   public void actionPerformed(ActionEvent e){

                                         System. out.println("Process print" );

                                  }

                           }

              );

              

              jbtSave.addActionListener(

                            new ActionListener(){

                                   public void actionPerformed(ActionEvent e){

                                         System. out.println("Process save" );

                                  }

                           }

              );

              

       }

       

        public static void main(String[] args)

       {

              JFrame frame = new AnonymousListenerDemo();

              frame.setTitle( "AnonymousListenerDemo");

              frame.setDefaultCloseOperation(JFrame. EXIT_ON_CLOSE);

              frame.setLocationRelativeTo( null);

              frame.pack();

              frame.setVisible( true);

       }

}

也可以只创建一个监听器,将这个监听器注册给按钮,让后让监听器检测出事件源.对于每种事件写不同的执行方法

可修改为: 

     ButtonListener listener = new ButtonListener();

     jbtNew.addActionListener(listener);

     jbtSave.addActionListener(listener);

     jbtOpen.addActionListener(listener);

     jbtPrint.addActionListener(listener);

     

     class ButtonListener implements ActionListener{

          public void actionPerformed(ActionEvent e){

               if(e.getSource() == jbtNew)

               {

                    System. out .println("Process new" );

               }

               else if(e.getSource() == jbtSave)

               {

                    System. out .println("Process save" );

               }

               else if(e.getSource() == jbtOpen)

               {

                    System. out .println("Process open" );

               }

               else if(e.getSource() == jbtPrint)

               {

                    System. out .println("Process print" );

               }

          }

     }

窗口事件：

     windows类或者windows任何子类都可能触发WindowEvent。JFrame是Windows的子类，因此也可以触发WindowEvent

激活窗口，关闭窗口，正在关闭窗口，变成非活动的窗口，最小化窗口，还原窗口或打开窗口。

import java.awt.event.*;

import javax.swing.*;

public class TestWindowEvent extends JFrame{

        public static void main(String[] args){

              TestWindowEvent frame = new TestWindowEvent();

              frame.setTitle( "TestWindowEvent");

              frame.setSize(220,80);

              frame.setDefaultCloseOperation(JFrame. EXIT_ON_CLOSE);

              frame.setLocationRelativeTo( null);

              frame.setVisible( true);

       }

       

        public TestWindowEvent(){

              addWindowListener( new WindowListener() {

                     

                      public void windowDeiconified(WindowEvent event)

                     {

                           System. out.println("Window deiconified" );

                     }

                     

                      public void windowIconified(WindowEvent event){

                           System. out.println("Window iconified" );

                     }

                     

                      public void windowActivated(WindowEvent evnet){

                           System. out.println("Window activated" );

                     }

                     

                      public void windowDeactivated(WindowEvent event){

                           System. out.println("Window deactivated" );

                     }

                     

                      public void windowOpened(WindowEvent event){

                           System. out.println("Window opened" );

                     }

                     

                      public void windowClosing(WindowEvent event){

                           System. out.println("Window closing" );

                     }

                     

                      public void windowClosed(WindowEvent event){

                           System. out.println("Window closed" );

                     }

              }

              );

       }

}

监听器接口适配器：

     因为WindowListener接口中的方法是抽象的，所以使用时必须事先所有方法。为了方便，java提供方便适配器的支持类。它提供监听器中所有方法的默认实现。每个XListener的方便监听器适配器命名为XAdapter.

     这样如果只对激活窗口事件感兴趣，使用WindowAdapter可以简化前面的例子。

     import java.awt.event.*;

import javax.swing.*;

public class AdapterDemo extends JFrame{

        public static void main(String[] args){

              AdapterDemo frame = new AdapterDemo();

              frame.setSize(220,80);

              frame.setLocationRelativeTo( null);

              frame.setDefaultCloseOperation(JFrame. EXIT_ON_CLOSE);

              frame.setTitle( "AdapterDemo");

              frame.setVisible( true);

       }

       

        public AdapterDemo(){

              addWindowListener( new WindowAdapter(){

                      public void windowActivated(WindowEvent event){

                           System. out.println("Window activated" );

                     }

              });

       }

}