[visibility_detector] iOS swipe back - Unexpected visibleFraction behaviour. It is just 1.0 or 0.0.

[HappyMakadiyaS]

Problem description

Steps to reproduce

1. Push new screen having Visibility Detector.
2. on onVisibilityChanged print value of visibleFraction
3. Using swipe Back gesture in iOS observe the printted value.

Expected behavior

While doing Swipe Back Gesture - Should get fraction values e.g. 0.74342, 0. 89294, etc

Actual behavior

But Getting just 1.0 or 0.0 in any state of visibility.

Environment

Device: iOS 17.4.1
Flutter Version: Flutter 3.22.1 • channel stable

Additional details

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.22.1, on macOS 14.4.1 23E224 darwin-arm64, locale en-IN)
[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 15.2)
[✓] Android Studio (version 2023.2)
[✓] VS Code (version 1.89.1)
[✓] Connected device (2 available)
[✓] Network resources

• No issues found!

Code Snippest

import 'package:flutter/material.dart';
import 'package:visibility_detector/visibility_detector.dart';

void main() {
  runApp(MaterialApp(
    title: 'Flutter Demo',
    theme: ThemeData(
      colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
      useMaterial3: true,
    ),
    home: const MyHomePage(),
  ));
}

class MyHomePage extends StatelessWidget {
  const MyHomePage({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("Visibility Detector"),
      ),
      body: Center(
        child: GestureDetector(
          onTap: () {
            Navigator.of(context).push(MaterialPageRoute(builder: (_) {
              return Scaffold(
                backgroundColor: Colors.grey,
                body: Center(
                  child: SizedBox(
                    height: 300,
                    child: PageView(
                      children: [
                        VisibilityDetector(
                          onVisibilityChanged: (info) {
                            print(info.visibleFraction);
                          },
                          key: const ValueKey("value"),
                          child: const ColoredBox(
                            color: Colors.yellow,
                            child: Text('Page 1'),
                          ),
                        ),
                        const ColoredBox(
                          color: Colors.red,
                          child: Text('Page 2'),
                        ),
                        const ColoredBox(
                          color: Colors.blue,
                          child: Text('Page 3'),
                        ),
                      ],
                    ),
                  ),
                ),
              );
            }));
          },
          child: const Text(
            'Push to Next Screen',
          ),
        ),
      ),
    );
  }
}

screen-recording-2024-06-03-at-70901-pm_5kd4253u.mp4