Widget _brightButton() => Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          SizedBox(height: 30),
          RaisedButton(
            onPressed: () {
              print("click");
            },
            child: Text(
              "colorBrightness:light",
              style: TextStyle(fontSize: 40),
            ),
            colorBrightness: Brightness.dark,
          ),
          SizedBox(height: 10),
          RaisedButton(
            onPressed: () {
              print("click");
            },
            child: Text(
              "colorBrightness:dark",
              style: TextStyle(fontSize: 40),
            ),
            colorBrightness: Brightness.light,
          ),
          SizedBox(height: 10),
          RaisedButton(
            onPressed: () {
              print("click");
            },
            child: Text(
              "colorBrightness:light\ntextTheme:accent",
              style: TextStyle(fontSize: 40),
            ),
            colorBrightness: Brightness.light,
            textTheme: ButtonTextTheme.accent,
          ),
        ],
      );