Java中创建事件监听器的五种方法

在Java中处理事件的办法最原始的方法如下

一.使用内部类

一个个设置Button然后创建一个内部类, 用ActionPerformed来实现按钮事件内容;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.*;

public class Test {
    public static void main(String[] args) {
        EventQueue.invokeLater(()->{
            JFrame myFrame = new ButtonFrame();
            myFrame.setTitle("Recluse");
            myFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            myFrame.setVisible(true);
        });
    }
}

class ButtonFrame extends JFrame{
    private JPanel myWindow;
    private static final int DEFAULT_WIDTH = 500;
    private static final int DEFAULT_HEIGHT = 500;

    public ButtonFrame(){
        this.setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);
        JButton greenButton = new JButton("Green");
        JButton yellowButton = new JButton("Yellow");
        JButton redButton = new JButton("Red");
        myWindow = new JPanel();
        myWindow.add(greenButton);
        myWindow.add(yellowButton);
        myWindow.add(redButton);
        this.add(myWindow);

        Colorbutton greenbut = new Colorbutton(Color.green);
        Colorbutton yellowbut = new Colorbutton(Color.yellow);
        Colorbutton redbut = new Colorbutton(Color.red);

        greenButton.addActionListener(greenbut);
        yellowButton.addActionListener(yellowbut);
        redButton.addActionListener(redbut);

    }

    private class Colorbutton implements ActionListener{
        private Color backgroundColor;

        public Colorbutton(Color c){
            backgroundColor = c;
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            myWindow.setBackground(backgroundColor);
        }
    }
    
}

二. 使用lambda表达式

但是这个方法比较繁琐,需要创建一个内部类, 其实有更简单的方法, 比如使用lambda表达式, 而不需要创建内部类, 我们可以把创建按钮和响应的部分放到一个方法里面, 如下:

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.*;

public class Test {
    public static void main(String[] args) {
        EventQueue.invokeLater(()->{
            JFrame myFrame = new ButtonFrame();
            myFrame.setTitle("Recluse");
            myFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            myFrame.setVisible(true);
        });
    }
}

class ButtonFrame extends JFrame{
    private JPanel myWindow;
    private static final int DEFAULT_WIDTH = 500;
    private static final int DEFAULT_HEIGHT = 500;

    public ButtonFrame(){
        myWindow = new JPanel();
        this.setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);
        myWindow.setPreferredSize(new Dimension(500,100));
        this.add(myWindow,BorderLayout.SOUTH);
        makeButton("Green", Color.GREEN);
        makeButton("Yellow",Color.YELLOW);
        makeButton("Blue",Color.BLUE);

    }

    public void makeButton(String name, Color backgroundcolor){
        JButton aButton = new JButton(name);
        myWindow.add(aButton);
        aButton.addActionListener(event->{myWindow.setBackground(backgroundcolor);});
    }

}

三. 使用匿名对象

当然使用lambda表达式肯定不是非用不可的, 以前的方法是使用匿名对象, 也是可以的:

        aButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                myWindow.setBackground(backgroundcolor);
            }
        });

四. 自身框架做事件源容器

其实可以直接用JFrame本身做事件源容器, 使ButtonFrame支持ActionListener接口, 需要把按钮定义在属性中, 然后在构造函数中添加的监听器中直接使用this 像这样:greenButton.addActionListener(this);然后在自己类中实现ActionPerformed方法, 使用Object source = e.getSource();获取到事件的更新源, 然后用判断语句来判断是哪个按钮的事件依次执行事件操作;

class ButtonFrame extends JFrame implements ActionListener{
    private JPanel myWindow;
    private static final int DEFAULT_WIDTH = 500;
    private static final int DEFAULT_HEIGHT = 500;
    JButton greenButton = new JButton("Green");
    JButton redButton = new JButton("Red");
    JButton blueButton = new JButton("Blue");

    public ButtonFrame(){
        myWindow = new JPanel();
        this.setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);
        myWindow.setPreferredSize(new Dimension(500,100));
        greenButton.addActionListener(this);
        redButton.addActionListener(this);
        blueButton.addActionListener(this);
        myWindow.add(greenButton);
        myWindow.add(redButton);
        myWindow.add(blueButton);
        this.add(myWindow,BorderLayout.SOUTH);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        Object source = e.getSource();
        if(source == greenButton) myWindow.setBackground(Color.GREEN);
        else if(source == redButton) myWindow.setBackground(Color.RED);
        else if(source == blueButton) myWindow.setBackground(Color.BLUE);
    }
}

五.使用EventHandler指定事件监听器

使用这样的方法EventHandler.create(ActionListener.class, frame, "loadData")创造一个ActionListener, 这种方法用lambda表达式就等同于event->frame.localData();
但是这个方法我还不会用呜呜呜