java - Allowing the "Enter" key to press the submit button, as opposed to only using MouseClick

Question

I'm learning Swing class now and everything about it. I've got this toy program I've been putting together that prompts for a name and then presents a JOptionPane with the message "You've entered (Your Name)". The submit button I use can only be clicked on, but I'd like to get it to work with the Enter button too. I've tried adding a KeyListener, as is recommended in the Java book I'm using (Eventful Java, Bruce Danyluk and Murtagh).

This is my code:

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

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;


public class NamePrompt extends JFrame{


    private static final long serialVersionUID = 1L;

    String name;

    public NamePrompt(){

        setLayout(new BorderLayout());

        JLabel enterYourName = new JLabel("Enter Your Name Here:");
        JTextField textBoxToEnterName = new JTextField(21);
        JPanel panelTop = new JPanel();
        panelTop.add(enterYourName);
        panelTop.add(textBoxToEnterName);

        JButton submit = new JButton("Submit");
        submit.addActionListener(new SubmitButton(textBoxToEnterName));
        submit.addKeyListener(new SubmitButton(textBoxToEnterName));
        JPanel panelBottom = new JPanel();
        panelBottom.add(submit);

        //Add panelTop to JFrame
        add(panelTop, BorderLayout.NORTH);
        add(panelBottom, BorderLayout.SOUTH);

        //JFrame set-up
        setTitle("Name Prompt Program");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        pack();
        setLocationRelativeTo(null);


    }



    public static void main(String[] args) {
        NamePrompt promptForName = new NamePrompt();
        promptForName.setVisible(true); 
    }


}

And this is the actionListener, keyListener class:

import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JTextField;


public class SubmitButton implements ActionListener, KeyListener {

    JTextField nameInput;


    public SubmitButton(JTextField textfield){
        nameInput = textfield;
    }

    @Override
    public void actionPerformed(ActionEvent submitClicked) {

        Component frame = new JFrame();
        JOptionPane.showMessageDialog(frame , "You've Submitted the name " + nameInput.getText());
    }

    @Override
    public void keyPressed(KeyEvent e) {
        if (e.getKeyCode()==KeyEvent.VK_ENTER){
            System.out.println("Hello");
        }
        Component frame = new JFrame();
        JOptionPane.showMessageDialog(frame , "You've Submitted the name " + nameInput.getText());

    }

    @Override
    public void keyReleased(KeyEvent arg0) {
        // TODO Auto-generated method stub

    }

    @Override
    public void keyTyped(KeyEvent arg0) {

    }
}

Answer 1

There is a simple trick for this. After you constructed the frame with all it buttons do this:

frame.getRootPane().setDefaultButton(submitButton);

For each frame, you can set a default button that will automatically listen to the Enter key (and maybe some other event's I'm not aware of). When you hit enter in that frame, the ActionListeners their actionPerformed() method will be invoked.

---

And the problem with your code as far as I see is that your dialog pops up every time you hit a key, because you didn't put it in the if-body. Try changing it to this:

@Override
public void keyPressed(KeyEvent e) {
    if (e.getKeyCode()==KeyEvent.VK_ENTER){
        System.out.println("Hello");

        JOptionPane.showMessageDialog(null , "You've Submitted the name " + nameInput.getText());
    }

}

---

UPDATE: I found what is wrong with your code. You are adding the key listener to the Submit button instead of to the TextField. Change your code to this:

SubmitButton listener = new SubmitButton(textBoxToEnterName);
textBoxToEnterName.addActionListener(listener);
submit.addKeyListener(listener);