keep jButton grey until jTextFields != null

Question

I have 4 jTextFields that I save the input to a file once a submit button is pressed. I want to be able to keep the submit button disabled until each field is at least not n

Answer 1

A simple runnable demo:

---

import java.awt.Dimension;
import java.awt.FlowLayout;
import java.util.List;
import java.util.Vector;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;

public class ButtonDemo extends JFrame implements DocumentListener {

    /**
     * 
     */
    private static final long serialVersionUID = -68704905659973315L;

    private JPanel panel = null;
    private JTextField field1 = null;
    private JTextField field2 = null;
    private JButton btn = null;
    private List textFields = null;

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

    private ButtonDemo() {
        this.panel = new JPanel();
        this.field1 = new JTextField("JTextField_1");
        this.field2 = new JTextField("JTextField_2");

        this.field1.getDocument().addDocumentListener(this);
        this.field2.getDocument().addDocumentListener(this);

        this.textFields = new Vector<>();
        this.textFields.add(field1);
        this.textFields.add(field2);
        this.btn = new JButton("Tests-Button");

        this.panel.setLayout(new FlowLayout());
        this.panel.add(field1);
        this.panel.add(field2);
        this.panel.add(btn);

        this.add(panel);

        this.setPreferredSize(new Dimension(200, 200));
        this.pack();
        this.setVisible(true);
    }

    @Override
    public void insertUpdate(DocumentEvent e) {
        updateButtonEnabledStatus(btn, textFields);
    }

    @Override
    public void removeUpdate(DocumentEvent e) {
        updateButtonEnabledStatus(btn, textFields);
    }

    @Override
    public void changedUpdate(DocumentEvent e) {
        updateButtonEnabledStatus(btn, textFields);
    }

    private void updateButtonEnabledStatus(JButton btn, List fields) {
        boolean enabled = true;
        for (JTextField field : fields) {
            if (field.getText().length() == 0) {
                enabled = false;
                break;
            }
        }
        btn.setEnabled(enabled);
    }
}