Draggable scrollable sheet with static content on bottom

draggable_scrollable_sheet.dart

import 'package:flutter/material.dart';

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

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

  static const String _title = 'Flutter Code Sample';

  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: MyApp._title,
      home: Scaffold(
        appBar: AppBar(title: const Text(MyApp._title)),
        body: Builder(builder: (context) {
          return Stack(
            children: [
              Container(
                color: Colors.blueGrey,
                child: Center(
                  child: Text("Content behind card"),
                ),
              ),
              DraggableScrollableSheet(
                initialChildSize: 0.25,
                maxChildSize: 0.75,
                minChildSize: 0.25,
                snap: true,
                builder: (context, scrollController) {
                  return Container(
                    color: Colors.white,
                    child: SingleChildScrollView(
                      controller: scrollController,
                      child: Center(
                        child: Text("Scrollable card"),
                      ),
                    ),
                  );
                },
              ),
              Align(
                alignment: Alignment.bottomCenter,
                child: Container(
                  height: 56,
                  color: Colors.green,
                  child: Center(child: Text("Button")),
                ),
              )
            ],
          );
        }),
      ),
    );
  }
}