WeatherMaster/lib/controllers/gradient.dart

import 'package:flutter/material.dart';
import '../utils/preferences_helper.dart';

class ScrollReactiveGradient extends StatefulWidget {
  final ScrollController scrollController;
  final LinearGradient baseGradient;
  final LinearGradient scrolledGradient;
  final ValueNotifier<bool>? headerVisibilityNotifier;

  const ScrollReactiveGradient({
    required this.scrollController,
    required this.baseGradient,
    required this.scrolledGradient,
    this.headerVisibilityNotifier,
    super.key,
  });

  @override
  State<ScrollReactiveGradient> createState() => _ScrollReactiveGradientState();
}

class _ScrollReactiveGradientState extends State<ScrollReactiveGradient> {
  bool _isScrolled = false;

  @override
  void initState() {
    super.initState();
    widget.scrollController.addListener(_onScroll);
    WidgetsBinding.instance.addPostFrameCallback((_) {
      _checkScroll();
    });
  }

  @override
  void didUpdateWidget(covariant ScrollReactiveGradient oldWidget) {
    super.didUpdateWidget(oldWidget);
    _checkScroll();
  }

  void _onScroll() {
    _checkScroll();
  }

  void _checkScroll() {
    final isNowScrolled = widget.scrollController.offset > 300;
    if (_isScrolled != isNowScrolled) {
      setState(() {
        _isScrolled = isNowScrolled;
      });

      if (widget.headerVisibilityNotifier != null &&
          widget.headerVisibilityNotifier!.value != isNowScrolled) {
        widget.headerVisibilityNotifier!.value = isNowScrolled;
      }
    }
  }

  @override
  void dispose() {
    widget.scrollController.removeListener(_onScroll);
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final useFullMaterialScheme =
        PreferencesHelper.getBool("OnlyMaterialScheme") ?? false;

    return Stack(
      children: [
        AnimatedOpacity(
          duration: const Duration(milliseconds: 300),
          opacity: _isScrolled ? 0 : 1,
          child: Container(
              decoration: !useFullMaterialScheme
                  ? BoxDecoration(
                      gradient: widget.baseGradient,
                    )
                  : BoxDecoration(
                      color:
                          Theme.of(context).colorScheme.surfaceContainerLow)),
        ),
        AnimatedOpacity(
          duration: const Duration(milliseconds: 300),
          opacity: _isScrolled ? 1 : 0,
          child: Container(
              decoration: !useFullMaterialScheme
                  ? BoxDecoration(
                      gradient: widget.scrolledGradient,
                    )
                  : BoxDecoration(
                      color:
                          Theme.of(context).colorScheme.surfaceContainerLow)),
        ),
      ],
    );
  }
}