home_screen.dart

  Widget firstChild() {
    return Row(
      mainAxisAlignment: MainAxisAlignment.spaceAround,
      children: <Widget>[
        AnimatedBuilder(
          animation: _arrowAnimationController,
          builder: (context, child) => Transform.rotate(
                angle: _arrowAnimation.value,
                child: Icon(
                  Icons.expand_more,
                  size: 50.0,
                  color: Colors.black,
                ),
              ),
        ),
        OutlineButton(
          color: Colors.white,
          textColor: Colors.black,
          padding: const EdgeInsets.all(12.0),
          child: Text('Start Icon Animation'),
          onPressed: () {
            _arrowAnimationController.isCompleted
                ? _arrowAnimationController.reverse()
                : _arrowAnimationController.forward();
          },
          splashColor: Colors.red,
        )
      ],
    );
  }