java - JButton Action 监听器不起作用

Question

我正在为 mt GUI 计算器上的 JButtons 设置 Action 监听器。为了测试这一点，我将其设置为当我按下计算器上的第一个按钮时将显示更改为新消息。但是，它不起作用。任何建议将不胜感激!非常感谢!

import java.awt.BorderLayout;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

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


public class GUICalculator extends JFrame{

    //Fields
    JButton[] buttons = new JButton[16];
    String s = "0.0";

    public GUICalculator(){
        Font font1 = new Font("Monospaced", Font.BOLD, 20);
        NumberListener numListen = new NumberListener();

        //Create JPanel p1
        JPanel p1 = new JPanel();
        p1.setLayout(new GridLayout(4, 4, 10, 20));
        String buttonValues[] = {"1", "2", "3", "+",
                                 "4", "5", "6", "-",
                                 "7", "8", "9", "*",
                                 "0", ".", "C", "/"};

        for(int i = 0; i < 16; i++){
            JButton button = new JButton(buttonValues[i]);
            buttons[i] = button;
            buttons[0].addActionListener(numListen);
            p1.add(buttons[i]);
        }

        //Create text field
        JTextField text = new JTextField();
        text.setText(s);
        text.setEditable(true);
        text.setFont(font1);

        //Create JPanel p2
        JPanel p2 = new JPanel();
        p2.setLayout(new BorderLayout(10, 20));
        p2.add(p1, BorderLayout.CENTER);
        p2.add(new JButton("="), BorderLayout.SOUTH);
        p2.add(text, BorderLayout.NORTH);

        //Add contents to the frame
        add(p2, BorderLayout.CENTER);
    }
    public static void main(String[] args) {

        GUICalculator frame = new GUICalculator();
        frame.setTitle("Calculator");
        frame.setSize(300,300);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }

    private class NumberListener implements ActionListener {

        public void actionPerformed(ActionEvent e) {
            if(e.getSource() == buttons[0]){
                s = "It worked!";
            }
            else{
                s = "It did not work";
            }
        }
    }
}

Answer 1

添加尚未在 ActionListener 中注册的按钮时，您正在创建一个新的按钮实例。替换

p1.add(new JButton(buttonValues[i]));

与

p1.add(buttons[i]);