2 event source & inner class DEMO(quote from Head First Java 2e)_java inner class handling event demo-优快云博客

本文展示了如何使用Java编程语言创建一个简单的GUI应用，其中包括动态生成随机颜色圆形和通过按钮实现图形元素的交互。通过实例演示了如何在Swing组件中利用事件监听器来改变标签文本和重新绘制图形界面。

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import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

@SuppressWarnings("serial")
class MyDrawPanel extends JPanel {
    public void paintComponent(Graphics g) {
        g.fillRect(0, 0, this.getWidth(), this.getHeight());
        int red = (int)(Math.random() * 255);
        int green = (int)(Math.random() * 255);
        int blue = (int)(Math.random() * 255);
        
        Color randomColor = new Color(red, green, blue);
        g.setColor(randomColor);
        g.fillOval(30, 30, 100, 100);
    }
}
public class TwoButtons {
    JFrame frame;
    JLabel label;
    
    public static void main(String[] args) {
        TwoButtons gui = new TwoButtons();
        gui.go();
    }
    
    public void go() {
        frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
        JButton labelButton = new JButton("Change Label");
        labelButton.addActionListener(new LabelListener());
        
        JButton colorButton = new JButton("Change Circle");
        colorButton.addActionListener(new ColorListener());
        
        label = new JLabel("I'm a label");
        MyDrawPanel drawPanel = new MyDrawPanel();
        
        frame.getContentPane().add(BorderLayout.SOUTH, colorButton);
        frame.getContentPane().add(BorderLayout.CENTER, drawPanel);
        frame.getContentPane().add(BorderLayout.EAST, labelButton);
        frame.getContentPane().add(BorderLayout.WEST, label);
        
        frame.setSize(300,  300);
        frame.setVisible(true);
    }
    
    class LabelListener implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            label.setText("Ouch!");
        }
    } // close inner class
    
    class ColorListener implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            frame.repaint();
        }
    } // close inner class
}