java - Action 事件最终变量？

Question

我有以下代码，但在第 19 行出现错误“无法将值分配给最终变量计数”，但我必须将此变量分配为最终变量才能在“LISTENER”中使用它。哪里错了？

import java.awt.event.*;
import javax.swing.*;


public class ButtonTester
{
    public static void main(String[] args)
    {
        JFrame frame = new JFrame();
        JButton button = new JButton();
        frame.add(button);

        final int count = 0;

        class ClickListener implements ActionListener
        {
            public void actionPerformed(ActionEvent event)
            {
                count++;
                System.out.println("I was clicked " + count + " times");
            }
        }

        ActionListener listener = new ClickListener();
        button.addActionListener(listener);

        frame.setSize(100,60);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

Answer 1

final 变量一旦赋值就不能修改。解决方案是使该变量成为您的 ClickListener 类的成员:

import java.awt.event.*;
import javax.swing.*;


public class ButtonTester
{
    public static void main(String[] args)
    {
        JFrame frame = new JFrame();
        JButton button = new JButton();
        frame.add(button);

        class ClickListener implements ActionListener
        {
            int count = 0;
            public void actionPerformed(ActionEvent event)
            {
                count++;
                System.out.println("I was clicked " + count + " times");
            }
        }

        ActionListener listener = new ClickListener();
        button.addActionListener(listener);

        frame.setSize(100,60);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}