ProgressButton.Dart

  Widget setUpButtonChild() {
    if (_state == 0) {
      return new Text(
        "Click Here",
        style: const TextStyle(
          color: Colors.white,
          fontSize: 16.0,
        ),
      );
    } else if (_state == 1) {
      return CircularProgressIndicator(
        valueColor: AlwaysStoppedAnimation<Color>(Colors.white),
      );
    } else {
      return Icon(Icons.check, color: Colors.white);
    }
  }