如何确定按钮已选中？

Question

The assignment is a basic voting system of picking between 3 people or 4th button is a "decline to answer"

I keep getting errors such as "Cannot find symbol"

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

public class Vote
{
    JLabel  label;

    public static void main (String[] args)

    {
        Vote sr = new Vote();
    }

    public Vote ()
    {

        JFrame frame = new JFrame("Please Choose your next President:");
        JRadioButton one = new JRadioButton("Name 1");
        JRadioButton two = new JRadioButton("Name 2");
        JRadioButton three = new JRadioButton("Name 3");
        JRadioButton four = new JRadioButton("I decline to answer");

        JPanel panel = new JPanel();
        panel.add(one);
        panel.add(two);
        panel.add(three);
        panel.add(four);

        ButtonGroup but = new ButtonGroup();

        but.add(one);
        but.add(two);
        but.add(three);
        but.add(four);

        one.addActionListener(new MyAction());
        two.addActionListener(new MyAction());
        three.addActionListener(new MyAction());
        four.addActionListener(new MyAction());

        label = new JLabel("Please Select a Canidate for President ");
        label.setHorizontalAlignment(JLabel.CENTER);
        frame.add(panel, BorderLayout.NORTH);
        frame.add(label, BorderLayout.CENTER);
        frame.setSize(400, 100);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public class MyAction implements ActionListener

    {
        public void actionPerformed (ActionEvent e)

        {
            if (jRadioButton.isSelected())
            {
                label.setText(e.getActionCommand());
                JOptionPane.showMessageDialog(null, "You have selected " +

                e.getActionCommand()
                        + " as the new President. Thank you for voting.");
            }
            else
            {
                label.setText(e.getActionCommand());
                JOptionPane.showMessageDialog(null, "You have selected " +

                e.getActionCommand() + " Thank you for voting.");
            }
        }
    }
}

So basic functions is to pick a name from 4 available radio buttons and upon selection of any buttons, a new windows comes up saying thank you for voting.

I would like to have different responses depending on the radio button pressed, so if a button pressed saying "I declined to answer" a proper response would be towards it.

Please check my If statement because i think where most of the errors are coming from and from a part of .isSelected .

Answer 1

if(jRadioButton.isSelected())

jRadioButton here is not defined.

You would want to get the source that triggered the event (ie one, two, three or four):

if(((JRadioButton)e.getSource()).isSelected())

This gets the object that triggered the event, casts it as a JRadioButton, and checks if that radio button is selected.

That should at least get rid of your "Cannot find symbol" error.

Answer 2

You have no object named jRadioButton . try changing

jRadioButton.isSelected()

to

((JRadioButton)e.getSource()).isSelected()

Also if you want to check if 4th JRadioButton was selected, then do the following:

four.setActionCommand("fourth");

and then in if statement

if ("fourth".equals(e.getActionCommand()) && ((JRadioButton)e.getSource()).isSelected())

it will check if action command maches fourth radio button and if it is selected