Widget _themeButton() => Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          SizedBox(height: 10),
          RaisedButton(
            onPressed: () {
              print("click");
            },
            child: Text(
              "textTheme:normal",
              style: TextStyle(fontSize: 40),
            ),
            textTheme: ButtonTextTheme.normal,
          ),
          RaisedButton(
            onPressed: () {
              print("click");
            },
            child: Text(
              "textTheme:accent",
              style: TextStyle(fontSize: 40),
            ),
            textTheme: ButtonTextTheme.accent,
          ),
          RaisedButton(
            onPressed: () {
              print("click");
            },
            child: Text(
              "textTheme:primary",
              style: TextStyle(fontSize: 40),
            ),
            textTheme: ButtonTextTheme.primary,
          ),
        ],
      );