目录一、初始代码架构二、需求分析2.1 写监听器2.2 发现问题2.3 使用匿名内部类优化代码2.4 优化完之后发现还是不是很优雅2.5 使用Lambda表达式再优化2.6 最终的代码三、ActionListener接口源码
一、初始代码架构
import java.awt.*;import java.awt.event.*;import javax.swing.*;public class Btn extends JFrame{ public static void main(String []args){ JFrame f = new JFrame("事件监听测试"); f.setBounds(0,0,300,400); f.addWindowListener(new WindowAdapter(){ public void windowClosing(WindowEvent e){ f.setVisible(false); f.dispose(); System.exit(0); } }); Container page = f.getContentPane(); page.setLayout(new FlowLayout()); JButton btn = new JButton("打印"); page.add(btn); f.setVisible(true); } }
运行的结果
二、需求分析
想要点击按钮的时候在终端打印一行信息（比如”按钮被点击”）
产品爸爸，提了新需求，不能实现也要创造办法实现的啦
2.1 写监听器
import java.awt.*;import java.awt.event.*;import javax.swing.*;public class Btn{ public static void main(String []args){ JFrame f = new JFrame("事件监听测试"); f.setBounds(0,0,300,400); f.addWindowListener(new WindowAdapter(){ public void windowClosing(WindowEvent e){ f.setVisible(false); f.dispose(); System.exit(0); } }); Container page = f.getContentPane(); page.setLayout(new FlowLayout()); JButton btn = new JButton("打印"); /** * 事件监听的使用步骤： * 1. 创建监听听 * 2. 将监听器注册到按钮上 * */ btnListener bl = new btnListener(); btn.addActionListener(bl); page.add(btn); f.setVisible(true); } }class btnListener implements ActionListener{ @Override public void actionPerformed(ActionEvent e){ System.out.println("按钮被点击了----"); } }
点击按钮的结果
2.2 发现问题
中规中矩地实现监听器地话，发现要另外写一个类实现ActionListener 接口地方法，使得代码架构显得比较臃肿。
2.3 使用匿名内部类优化代码
import java.awt.*;import java.awt.event.*;import javax.swing.*;public class Btn{ public static void main(String []args){ JFrame f = new JFrame("事件监听测试"); f.setBounds(0,0,300,400); f.addWindowListener(new WindowAdapter(){ public void windowClosing(WindowEvent e){ f.setVisible(false); f.dispose(); System.exit(0); } }); Container page = f.getContentPane(); page.setLayout(new FlowLayout()); JButton btn = new JButton("打印"); /** * 事件监听的使用步骤： * 1. 创建监听听 * 2. 将监听器注册到按钮上 * */ ActionListener bl = new ActionListener(){ @Override public void actionPerformed(ActionEvent e){ System.out.println("匿名内部类优化----"); } }; btn.addActionListener(bl); page.add(btn); f.setVisible(true); } }class btnListener implements ActionListener{ @Override public void actionPerformed(ActionEvent e){ System.out.println("按钮被点击了----"); } }
2.4 优化完之后发现还是不是很优雅
因为每次监听都有重复代码
@Override public void actionPerformed(ActionEvent e){ System.out.println("匿名内部类优化----"); }
2.5 使用Lambda表达式再优化
import java.awt.*;import java.awt.event.*;import javax.swing.*;public class Btn{ public static void main(String []args){ JFrame f = new JFrame("事件监听测试"); f.setBounds(0,0,300,400); f.addWindowListener(new WindowAdapter(){ public void windowClosing(WindowEvent e){ f.setVisible(false); f.dispose(); System.exit(0); } }); Container page = f.getContentPane(); page.setLayout(new FlowLayout()); JButton btn = new JButton("打印"); /** * 事件监听的使用步骤： * 1. 创建监听听 * 2. 将监听器注册到按钮上 * */ // ActionListener bl = new ActionListener(){ // @Override // public void actionPerformed(ActionEvent e){ // System.out.println("匿名内部类优化----"); // } // }; // btn.addActionListener(bl); btn.addActionListener((e)->{ System.out.println("使用Lambda表达式优化"); }); page.add(btn); f.setVisible(true); } }class btnListener implements ActionListener{ @Override public void actionPerformed(ActionEvent e){ System.out.println("按钮被点击了----"); } }
结果
2.6 最终的代码
import java.awt.*;import java.awt.event.*;import javax.swing.*;public class Btn{ public static void main(String []args){ JFrame f = new JFrame("事件监听测试"); f.setBounds(0,0,300,400); f.addWindowListener(new WindowAdapter(){ public void windowClosing(WindowEvent e){ f.setVisible(false); f.dispose(); System.exit(0); } }); Container page = f.getContentPane(); page.setLayout(new FlowLayout()); JButton btn = new JButton("打印"); btn.addActionListener((e)->{ System.out.println("使用Lambda表达式优化"); }); page.add(btn); f.setVisible(true); }}
三、ActionListener接口源码
/* * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved. * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */package java.awt.event;import java.util.EventListener;/** * The listener interface for receiving action events. * The class that is interested in processing an action event * implements this interface, and the object created with that * class is registered with a component, using the component's * {@code addActionListener} method. When the action event * occurs, that object's {@code actionPerformed} method is * invoked. * * @see ActionEvent * @see <a href="https://docs.oracle.com/javase/tutorial/uiswing/events/actionlistener.html" rel="external nofollow" >How to Write an Action Listener</a> * * @author Carl Quinn * @since 1.1 */public interface ActionListener extends EventListener { /** * Invoked when an action occurs. * @param e the event to be processed */ public void actionPerformed(ActionEvent e);}
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