Answer by Jalil for How to delete/detect any emoji as a whole from a string in Flutter?

You can do a method like this one

bool isValid(String prevString, String newString){  if (prevString == newString)    return true;  else return false; }

then in your keyboard you validate with an onChange property

TextField(  onChanged: (text) {    isValid(varYouHad ,text); //validate  },);