// Modify the code in the _handleSubmitted method definition.

void _handleSubmitted(String text) {
  _textController.clear();
    ChatMessage message = new ChatMessage(                         //new
      text: text,                                                  //new
    );                                                             //new
    setState(() {                                                  //new
      _messages.insert(0, message);                                //new
    });                                                            //new
 }