Programmatically scroll to top

.dart

class ScrollToTopWidgetWrapper extends StatefulWidget {
  final Widget child;
  const ScrollToTopWidgetWrapper({super.key, required this.child});

  @override
  State<ScrollToTopWidgetWrapper> createState() =>
      _ScrollToTopWidgetWrapperState();
}

class _ScrollToTopWidgetWrapperState extends State<ScrollToTopWidgetWrapper> {
  final scrollController = ScrollController();
  bool isVisible = false;
  @override
  void initState() {
    scrollController.addListener(_scrollListener);
    super.initState();
  }

  _scrollListener() {
    if (scrollController.offset > 0.0) {
      setState(() {
        isVisible = true;
      });
    }
    if (scrollController.offset <= 0.0) {
      setState(() {
        isVisible = false;
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Stack(
      children: [
        SingleChildScrollView(
            controller: scrollController, child: widget.child),
        isVisible
            ? Positioned(
                bottom: 16,
                right: 8,
                child: AnimatedFloatingButton(
                    onPressed: () => scrollController.animateTo(0.0,
                        duration: Durations.long4, curve: Curves.easeInOut)),
              )
            : const Center()
      ],
    );
  }
}



class AnimatedFloatingButton extends StatefulWidget {
  final VoidCallback onPressed;
  const AnimatedFloatingButton({super.key, required this.onPressed});

  @override
  State<AnimatedFloatingButton> createState() => _AnimatedFloatingButtonState();
}

class _AnimatedFloatingButtonState extends State<AnimatedFloatingButton>
    with SingleTickerProviderStateMixin {
  late AnimationController _controller;
  late Animation<Offset> animation;
  @override
  void initState() {
    super.initState();
    _controller =
        AnimationController(vsync: this, duration: const Duration(seconds: 4));
    animation =
        Tween(begin: const Offset(5, 0), end: const Offset(0, 0)).animate(_controller);

    _controller.forward();
    
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return SlideTransition(
      position: animation,
      child: CustomButton(
          color: Colors.green,
          height: 60,
          width: 60,
          radius: 50,
          onPressed: widget.onPressed,
          child: const Icon(
            Icons.keyboard_arrow_up,
            size: 34,
            color: Colors.white,
          )),
    );
  }
}