Update jTextField in another swing gui class

Question

My problem is to update jTextField1 (update province) in class Province.java. The first GUI showing up is AddAddress which contains 4 fields ( jTextField ) to be filled in : province ( jTextField1), district(2), ward(3) . Each time double-click on jTextField1 or 2 or 3 or 4 a new JFrame appears showing province, district or ward list. After clicking, it returns back to the first GUI and the province/district/ward clicked is updated.

Answer 1

Do not use JFrame in situations like that. Actually using multiple frames in one application is a bad practice. Please read here: The Use of Multiple JFrames: Good or Bad Practice?.

I suggest you to use a JDialog to select province etc.

Here is a simple example:

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

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JTextField;

public class JDialogDemo extends JFrame {

    public JDialogDemo() {

        final MyDialog dialog = new MyDialog(this);

        final JTextField provinceField = new JTextField(10);

        JButton button = new JButton("Show Dialog");
        button.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                dialog.pack();
                dialog.setLocationRelativeTo(JDialogDemo.this);

                dialog.setVisible(true);

                provinceField.setText(dialog.getSelectedProvince());
            }
        });

        setLayout(new FlowLayout());
        add(provinceField);
        add(button);

        setSize(400, 400);
        setVisible(true);
    }

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

class MyDialog extends JDialog {

    private String selectedProvince;

    public MyDialog(Frame owner) {
        super(owner, true);

        setTitle("Provinces");

        final JList<String> list = new JList<String>(new String[]{"province1", "province2", "province3"});
        add(list);

        JButton okButton = new JButton("Ok");
        okButton.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                selectedProvince = list.getSelectedValue();
                setVisible(false);
            }
        });

        add(okButton, BorderLayout.SOUTH);
    }

    public String getSelectedProvince() {
        return selectedProvince;
    }

}

Edit:

Edit your jTextField1MouseClicked method

private void jTextField1MouseClicked(java.awt.event.MouseEvent evt) {//GEN-FIRST:event_jTextField1MouseClicked
        // TODO add your handling code here:
      if(evt.getClickCount() == 2){
            AddProvince provinceDialog = new AddProvince();
            provinceDialog.setVisible(true);
            jTextField1.setText(provinceDialog.getSelectedProvince());
      }
}

Then make AddProvince extends from JDialog. And add a method which return the selected province.