Using flutter_portal to create a popover that allows the base view to remain interactive

main.dart

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

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  static const title = 'Spike Overlay TextField';

  @override
  Widget build(BuildContext context) {
    return Portal(
      child: MaterialApp(
        title: MyApp.title,
        home: MyHomePage(),
      ),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key}) : super(key: key);

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

class _MyHomePageState extends State<MyHomePage> {
  var _portalVisible = false;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(MyApp.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Padding(
              padding: const EdgeInsets.all(20),
              child: TextField(),
            ),
          ],
        ),
      ),
      floatingActionButton: PortalEntry(
        visible: _portalVisible,
        portalAnchor: Alignment.bottomRight,
        childAnchor: Alignment.topLeft,
        portal: SizedBox(
          height: 150,
          width: 150,
          child: Material(
            child: Stack(
              alignment: Alignment.topRight,
              children: [
                /// Placeholder indicator
                Placeholder(
                  color: Colors.grey.shade200,
                ),

                /// Close button
                IconButton(
                  icon: Icon(Icons.close),
                  onPressed: () {
                    setState(() {
                      _portalVisible = false;
                    });
                  },
                ),
              ],
            ),
          ),
        ),
        child: FloatingActionButton(
          onPressed: () {
            setState(() {
              _portalVisible = true;
            });
          },
          tooltip: 'Increment',
          child: Icon(Icons.add),
        ),
      ),
    );
  }
}

pubspec.yaml

name: spike_overlay_text_field
description: A new Flutter project.
publish_to: "none"
version: 1.0.0+1

environment:
  sdk: ">=2.7.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter

  cupertino_icons: ^1.0.2
  flutter_portal: ^0.3.0

dev_dependencies:
  flutter_test:
    sdk: flutter

flutter:
  uses-material-design: true