SliverIgnorePointer.dart

import 'package:flutter/material.dart';

void main() => runApp(MaterialApp(home: MyApp()));

class MyApp extends StatefulWidget {
  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  bool _visible = true;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: CustomScrollView(
        slivers: <Widget>[
          SliverToBoxAdapter(
            child: Image.network(
              "https://1gew6o3qn6vx9kp3s42ge0y1-wpengine.netdna-ssl.com/wp-content/uploads/prod/2020/10/HERO-ART-microsoft_azure_1920x1000_nologo.jpg",
              width: double.infinity,
              height: 300,
              fit: BoxFit.cover,
            ),
          ),
          SliverIgnorePointer(
            ignoring: true,
            ignoringSemantics: true,
            sliver: SliverPadding(
              padding: EdgeInsets.only(top: 18),
              sliver: SliverToBoxAdapter(
                  child: FloatingActionButton(
                onPressed: () {
                  setState(() {
                    _visible = !_visible;
                  });
                },
                child:
                    Icon(!_visible ? Icons.visibility : Icons.visibility_off),
              )),
            ),
          ),
        ],
      ),
    );
  }
}