gesture_1.dart

class _MyHomePageState extends State<MyHomePage> {
  final GlobalKey sliderKey = GlobalKey();
  
  // ...
  
  static const platform = const MethodChannel('sample/gesture');

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) => _setupNavigationSafeZone());
  }
  
  // ...

  void _setupNavigationSafeZone() {
    final context = sliderKey.currentContext;

    if (context == null) {
      debugPrint("Slider is not in hierarchy yet");
      return;
    }

    final box = context.findRenderObject() as RenderBox;
    final position = box.localToGlobal(Offset.zero);

    final ratio = MediaQuery.of(context).devicePixelRatio;
    final verticalThreshold = 10 * ratio;

    final left = position.dx * ratio;
    final top = position.dy * ratio;
    final right = left + box.size.width * ratio;
    final bottom = top + box.size.height * ratio;
    final rect = Rect.fromLTRB(left, top - verticalThreshold, right, bottom + verticalThreshold);

    _setSystemGestureExclusionRects([rect]);
  }

  Future<void> _setSystemGestureExclusionRects(List<Rect> rects) async {
    try {
      final rectsAsMaps = rects
          .map((r) => {"top" : r.top.floor(), "left" : r.left.floor(), "bottom" : r.bottom.floor(), "right" : r.right.floor()})
          .toList();
      await platform.invokeMethod('setSystemGestureExclusionRects', rectsAsMaps);
    } on PlatformException catch (e) {
      print("Failed to set system gesture exclusion rects: ${e.toString()}");
    }
  }
}