code: public void setPrefix(CharSequence p) {
          //Have to clear and set the actual text before saving the prefix to avoid the prefix filter
          CharSequence prevPrefix = prefix;
          prefix = p;
          Editable text = getText();
          if (text != null) {
              internalEditInProgress = true;
              if (prevPrefix != null) {
                  text.replace(0, prevPrefix.length(), p);
              } else {
                  text.insert(0, p);
              }
              internalEditInProgress = false;
          }
          //prefix = p;
  
          updateHint();
      }
docs: A String of text that is shown before all the tokens inside the EditText
  (Think "To: " in an email address field. I would advise against this: use a label and a hint.
  
  @param p String with the hint