Passing JRadioSelection to an ActionLIstener class

Question

For my application, I created two JRadioButton grouped into a "selection" ButtonGroup. I added an ActionListener called "SelectionListener." When I check if my RadioButton is selected using isSelected(), it appears that my selection is not getting passed over to the ActionListener.

public static void main(String[] args) {
    JRadioButton monthlyRadioButton = new JRadioButton("Monthly Payment", true);
    JRadioButton loanAmountButton = new JRadioButton("Loan Amount");
    ButtonGroup selection = new ButtonGroup();
    selection.add(monthlyRadioButton);
    selection.add(loanAmountButton);
    monthlyRadioButton.addActionListener(new SelectionListener());
    loanAmountButton.addActionListener(new SelectionListener());
} 

SelectionListener.java

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

class SelectionListener implements ActionListener {
    public void actionPerformed(ActionEvent event){
      if(event.getSource() == monthlyRadioButton)
        System.out.println("You clicked Monthly");
      else
        System.out.println("You clicked Loan Amount");

    }
}

The parameters monthlyRadioButton is not getting passed over to my SelectionListener class. I'm getting an error that it is not being resolved.

How do I pass the monthlyRadioButton in my main method over to my SelectionListener class?

Answer 1

You car retrieve the sender of the event is being handled.

Something like:

class SelectionListener implements ActionListener {
    private JComponent monthlyRadioButton;
    private JComponent loanAmountButton;

    public SelectionListener(JComponent monthlyRadioButton, JComponent loanAmountButton) {
        this.monthlyRadioButton = monthlyRadioButton;
        this.loanAmountButton = loanAmountButton;
    }

    public void actionPerformed(ActionEvent event){
        if(event.getSource() == monthlyRadioButton)
            System.out.println("You clicked Monthly");
        else if(event.getSource() == loanAmountButton)
            System.out.println("You clicked Loan Amount");
    }
}

On your main method you could instantiate it like:

    monthlyRadioButton.addActionListener(new SelectionListener(monthlyRadioButton, loanAmountButton));

Answer 2

You create a new variable in main named monthlyRadioButton (thius is local to main, not visible from anywhere else), but check another (not listed in your code) in actionPerformed

Answer 3

The actionListeners registered on JRadioButton are called before the radio button becomes selected. That is why your isSelected() invocations return false (or to be more precise: they return the actual value, before the change).

If you want to handle state changes, you should register a ChangeListener.