How can i animate a SliverAppBar to hide it on scrolling a TabBarView

Question

I want to animate a SliverAppBar that is defined in a NestedScrollView. I want to have the same animation Whatsapp has while scrolling to the camera tab but using Animated Widgets as Slivers parent is forbidden. how can i achieve that? here is an expensive way to do it but it's not performance-friendly

Answer 1

You can set your app bar like this to hide AppBar when the user scrolls the view

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

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    const title = 'Floating App Bar';

    return MaterialApp(
      title: title,
      home: Scaffold(
        // No appbar provided to the Scaffold, only a body with a
        // CustomScrollView.
        body: CustomScrollView(
          slivers: [
            // Add the app bar to the CustomScrollView.
            const SliverAppBar(
              // Provide a standard title.
              title: Text(title),
              // Allows the user to reveal the app bar if they begin scrolling
              // back up the list of items.
              floating: true,
              // Display a placeholder widget to visualize the shrinking size.
              flexibleSpace: Placeholder(),
              // Make the initial height of the SliverAppBar larger than normal.
              expandedHeight: 200,
            ),
            // Next, create a SliverList
            SliverList(
              // Use a delegate to build items as they're scrolled on screen.
              delegate: SliverChildBuilderDelegate(
                // The builder function returns a ListTile with a title that
                // displays the index of the current item.
                (context, index) => ListTile(title: Text('Item #$index')),
                // Builds 1000 ListTiles
                childCount: 1000,
              ),
            ),
          ],
        ),
      ),
    );
  }
}