Java Swing How to - Enable or disable a JButton based on JTextField content

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Question

We would like to know how to enable or disable a JButton based on JTextField content.

Answer

   /* w  ww.  j  av a  2s . co m*/


import javax.swing.JButton;
import javax.swing.JOptionPane;
import javax.swing.JTextField;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.Document;

public class Main {

  public Main() {
    JButton button = new JButton("foo");
    JTextField textField = new JTextField(10);
    Document document = textField.getDocument();
    document.addDocumentListener(new JButtonStateController(button));
  
    JOptionPane.showMessageDialog(null, textField);
    
  }

}
class JButtonStateController implements DocumentListener {
 JButton button;
  
  JButtonStateController(JButton button) {
     this.button = button ;
  }

  public void changedUpdate(DocumentEvent e) {
    disableIfEmpty(e);
  }

  public void insertUpdate(DocumentEvent e) {
    disableIfEmpty(e);
  }

  public void removeUpdate(DocumentEvent e) {
    disableIfEmpty(e);
  }

  public void disableIfEmpty(DocumentEvent e) {
    button.setEnabled(e.getDocument().getLength() > 0);
  }
}

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