How to disable / enable dialog negative positive buttons?

Question

Please look at the custom dialog below. I have an edittext field on the dialog and if the text field is empty I would like to disable the positiveButton. I can

Answer 1

if (editTextEmailAddress.getText().toString().length() == 0) {
    btnCancelCross.setEnabled(false);
} else {
    btnCancelCross.setEnabled(true);
}

That might help you thanks.