用户界面-Java gui不会在动作侦听器侦听事件后打印

Question

Code不会在ide文本字段中输出"Works"消息。如何使程序在ide的文本中输出我的消息？非常感谢。

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class test extends JFrame {
    private JButton button1;
    public test() {
        JFrame frame = new JFrame("Test Program");
        JPanel panel = new JPanel();
        JButton button1 = new JButton("Click me PLEASE!");
        panel.setBackground(Color.red);
        panel.add(button1);
        frame.getContentPane().add(panel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        frame.setSize(800, 800);
        Listener1 listen = new Listener1();
        button1.addActionListener(listen);
    }
    public static void main(String[] args) {
        new test();
    }
    private class Listener1 implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            if (event.getSource() == button1) {
                System.out.println("Works!");
            }
        }
    }

Answer 1

您正在比较的button1实例不是触发事件的button1实例。。。

基本上，你是在跟踪你的变量。。。

// Declare instance variable here...
private JButton button1;
public test() {
    //...
    // Redeclared as local variable here
    JButton button1 = new JButton("Click me PLEASE!");

如果添加。。。

System.out.println("button1 = " + button1);

给你Listener1，你会发现它是null

删除本地声明。。。

    button1 = new JButton("Click me PLEASE!");