Pass value from one JtextField to another?

Question

//New to java swing and need help getting the text in the first Jtextfield to display in the //second second jtextfield???? Im young and just starting out in java and need some help. below is the code i have done already thanks

import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class lab4 extends JFrame implements ActionListener {

    int numClicks = 0;
    String text = null;

    public lab4() {
        setSize(1200, 700);
        setVisible(true);
        JButton button = new JButton("Hello i am a button");
        button.addActionListener(this);
        JPanel panel = new JPanel();
        panel.setBorder(BorderFactory.createLineBorder(Color.BLACK, 2));

        panel.add(button);
        this.add(panel);

        JMenuBar menubar = new JMenuBar();
        this.setJMenuBar(menubar);
        JMenu file = new JMenu("File");
        menubar.add(file);
        JMenuItem open = new JMenuItem("Open File");
        file.add(open);

        final JTextField myField = new JTextField(10);
        myField.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String text = myField.getText();
//System.out.println("Hello");

            }
        });

        final JTextField myField2 = new JTextField(10);
        yField2.setText(myField.getText());
        panel.add(myField);

        panel.add(myField2);
        setVisible(true);
    }
}

    public static void main(String[] args) {
        new lab4();

    }

    public void actionPerformed(ActionEvent e) {
        numClicks++;
        System.out.println("The button has been clicked " + numClicks + " times");

    }
}

Answer 1

Yes, you are doing ok. If more then one work going to happen in sequence on one action event, then you need to put the sequence inside the corresponding actionPerformed function. So:

myField.addActionListener(new ActionListener(){
    public void actionPerformed(ActionEvent e){
    String text = myField.getText();
    myField2.setText(text);

}
});

JComponents listeners mean that they will listen and respond only when an action event occur. They will be notified by the instance of ActionListener registered to event source(JCompnent) with addActionListener() function as you have done.

One more thing to note: you can't access a field in any statement before even declaring it. Compiler's need to know the information about the field before doing anything with it. So you must declare myField2 before the accessing-code of it, such as, myField1's anonymous class ActionListener actionPerformed function.

Tutorial Resources:

1. Writing Event Listeners
2. Anonymous Class

Answer 2

You can share the model:

JTextField textField1 = new JTextField(...);
JTextField textField2 = new JTextField(...);
textField2.setDocument( textField1.getDocument() ):

Now whenever you type text in either text field the other will also be updated.