Java - Check if JTextField is empty or not

Question

So I got know this is a popular question and already found the solution. But when I try this it doesn\'t work properly.

My JTextField is empty and the button isn\'t

Answer 1

What you need is something called Document Listener. See How to Write a Document Listener.

Answer 2

Try with keyListener in your textfield

jTextField.addKeyListener(new KeyListener() {

        @Override
        public void keyTyped(KeyEvent e) {
        }

        @Override
        public void keyPressed(KeyEvent e) {
            if (text.getText().length() >= 1) {
                button.setEnabled(true);
            } else {
                button.setEnabled(false);
            }
        }

        @Override
        public void keyReleased(KeyEvent e) {
        }

    });

Answer 3

if(name.getText().hashCode() != 0){
    JOptionPane.showMessageDialog(null, "not empty");
}
else{
    JOptionPane.showMessageDialog(null, "empty");
}

Answer 4

For that you need to add change listener (a DocumentListener which reacts for change in the text) for your JTextField, and within actionPerformed(), you need to update the loginButton to enabled/disabled depending on the whether the JTextfield is empty or not.

Below is what I found from this thread.

yourJTextField.getDocument().addDocumentListener(new DocumentListener() {
  public void changedUpdate(DocumentEvent e) {
    changed();
  }
  public void removeUpdate(DocumentEvent e) {
    changed();
  }
  public void insertUpdate(DocumentEvent e) {
    changed();
  }

  public void changed() {
     if (yourJTextField.getText().equals("")){
       loginButton.setEnabled(false);
     }
     else {
       loginButton.setEnabled(true);
    }

  }
});

Answer 5

Well, the code that renders the button enabled/disabled:

if(name.getText().equals("")) {
    loginbt.setEnabled(false);
}else {
    loginbt.setEnabled(true);
}

must be written in javax.swing.event.ChangeListener and attached to the field (see here). A change in field's value should trigger the listener to reevaluate the object state. What did you expect?