尝试在单击按钮时显示 JOptionPane

Question

我试图在单击按钮时显示 JOptionPane，但我一直收到错误消息，说我在构造函数中缺少 return 语句。任何帮助将非常感激。谢谢到目前为止，这是我的代码。

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

public class lab9Part1 extends JFrame implements ActionListener {
    JButton button = new JButton("Show Message Dialog");
    JFrame box = new JFrame();

    public lab9Part1() {
        super("lab9Part1");
        Container c = getContentPane();
        button.addActionListener(this);
        c.add(button, BorderLayout.SOUTH);
        setVisible(true);
        setSize(500,500);
    }

    public static Void main (String [] args){
        JFrame frame = new lab9Part1();
    }

    public void actionPerformed(ActionEvent e){
        if (e.getSource()== button) {
            JOptionPane.showMessageDialog(box,"hello","This is Cal and this is my first message dialog", JOptionPane.INFORMATION_MESSAGE);
        }
    }
}

Answer 1

您在 main 的方法声明中使用了 Void（大写 V）而不是 void（小写 v）。应该是：

 public static void main (String [] args){

        JFrame frame = new lab9Part1();

 }

尝试在单击按钮时显示 JOptionPane

Trying to display JOptionPane on button click

java

swing

compiler-errors

joptionpane