Drawer in a transparent page route

drawer.dart

//
// [Author] Alex (https://github.com/AlexV525)
// [Date] 2022/6/7 16:35
//

import 'package:flutter/material.dart';

/// A wrapped [Drawer] that typically useful when placed in a transparent route.
class CustomDrawer extends StatefulWidget {
  const CustomDrawer({
    Key? key,
    required this.builder,
    this.drawerAlignment = DrawerAlignment.start,
    this.scrimColor = Colors.transparent,
    this.fractionalWidthFactor = 1.0,
    this.fractionalHeightFactor = 1.0,
    this.fractionalAlignment = AlignmentDirectional.centerStart,
  }) : super(key: key);

  final WidgetBuilder builder;
  final DrawerAlignment drawerAlignment;
  final Color scrimColor;
  final double fractionalWidthFactor;
  final double fractionalHeightFactor;
  final AlignmentGeometry fractionalAlignment;

  @override
  State<CustomDrawer> createState() => _CustomDrawerState();
}

class _CustomDrawerState extends State<CustomDrawer> {
  final GlobalKey<DrawerControllerState> _drawerControllerKey = GlobalKey();
  final ValueNotifier<int> _pointers = ValueNotifier<int>(0);
  final ValueNotifier<bool> _isDrawerOpen = ValueNotifier<bool>(true);
  bool _isDrawerClosing = false;

  @override
  void initState() {
    super.initState();
    _pointers.addListener(_pointerListener);
  }

  @override
  void dispose() {
    _pointers.dispose();
    _isDrawerOpen.dispose();
    super.dispose();
  }

  void _pointerListener() {
    if (_pointers.value == 0 && _isDrawerClosing) {
      WidgetsBinding.instance.addPostFrameCallback((_) {
        Navigator.of(context).pop();
      });
    }
  }

  void _drawerCallback(bool isOpened) {
    if (!isOpened && !_isDrawerClosing) {
      _isDrawerClosing = true;
      if (_pointers.value == 0) {
        Navigator.of(context).pop();
      }
    }
  }

  Future<bool> _onWillPop() async {
    if (!_isDrawerClosing) {
      _isDrawerClosing = true;
      _drawerControllerKey.currentState?.close();
    }
    return false;
  }

  Widget _buildDrawer(BuildContext context, bool isDrawerOpen, Widget? child) {
    return DrawerController(
      key: _drawerControllerKey,
      alignment: widget.drawerAlignment,
      enableOpenDragGesture: false,
      isDrawerOpen: isDrawerOpen,
      drawerCallback: _drawerCallback,
      scrimColor: widget.scrimColor,
      child: child!,
    );
  }

  @override
  Widget build(BuildContext context) {
    Widget child = widget.builder(context);
    if (widget.fractionalWidthFactor < 1 || widget.fractionalHeightFactor < 1) {
      child = FractionallySizedBox(
        alignment: widget.fractionalAlignment,
        widthFactor: widget.fractionalWidthFactor,
        heightFactor: widget.fractionalHeightFactor,
        child: child,
      );
    }
    return WillPopScope(
      onWillPop: _onWillPop,
      child: Listener(
        onPointerDown: (_) => _pointers.value++,
        onPointerUp: (_) => _pointers.value--,
        child: ValueListenableBuilder<bool>(
          valueListenable: _isDrawerOpen,
          builder: _buildDrawer,
          child: child,
        ),
      ),
    );
  }
}