Java基础学习之Swing事件监听
作者：一腔诗意醉了酒
今天学习java的Swing库,创建桌面应用的时候,突然发现有些按钮需要特定的功能响应,故来研究一番Swing的事件监听,文中有非常详细的介绍及代码示例,需要的朋友可以参考下
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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