java - 在 java 中使用 swing 时出现错误消息的对话框

Question

我不是一个好的java程序员。当我使用这种编码时，我遇到了一些错误。有人可以帮我吗？

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.JOptionPane;

public class test4 implements ActionListener

{

    public static void main(String[] args)throws Exception

    {

        JFrame f=new JFrame("test 4");

        JButton b=new JButton("gud morning");

        JButton b1=new JButton("yes or no");

        b.addActionListener(this);

        b1.addActionListener(this);

        Container content=f.getContentPane();

        content.add(b,BorderLayout.NORTH);

        content.add(b1,BorderLayout.SOUTH);

        f.setVisible(true);

        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        f.setSize(100,100);

        }
}

public void actionPerformed(ActionEvent e)

{

    String s=e.getActionCommand();

    if(s.equals("gud morning"))

    {

        JOptionPane.showMessageDialog(f,"gud morning","My Message");

    }

    else if(s.equals("yes or no"))

    {


        if(JOptionPane.showConfirmMessageDialog(f,"yes or no","it is also my message",JOptionPane.YES_NO_CANCEL_OPTION)==0);

        {

            JOptionPane.showMessageDialog(f,"u clicked yes button");

        }

        else

        {

            JOptionPane.showMessageDialog(f,"u clicked no button");

        }

    }

}

我收到此错误：

\ram>javac test4.java test4.java:22: error: class, interface, or enum expected public void actionPerformed(ActionEvent e) ^ test4.java:25: error: class, interface, or enum expected if(s.equals("gud morning")) ^ test4.java:28: error: class, interface, or enum expected } ^ 3 errors

Answer 1

您的if语句被 a 终止，;这将使else分支不正确。去除;

if(JOptionPane.showConfirmMessageDialog(f,"yes or no","it is also my message",JOptionPane.YES_NO_CANCEL_OPTION)==0);

变成：

if(JOptionPane.showConfirmMessageDialog(f,"yes or no","it is also my message",JOptionPane.YES_NO_CANCEL_OPTION)==0)

}在开始之前，您还有一个额外的花括号actionPerformed。