Flutter doesn't rebuild if there are animated Widgets

Question

I have encountered a weird problem in Flutter. In my app, I'm showing a splash screen before my models and other things are initialized, then I show a different Widget for the duration of the application.

Things work as expected - unless the first Widget contains anything that animates (CircularProgressIndicator for example)! In that case, the build method is never called again when I call setState - even if I call setState several seconds later from a Timer.

If I hit "Hot Restart" or "Hot Reload" in the IDE, the app is rebuilt as expected. It also works if the first Widget doesn't contain a CircularProgressIndicator, or any other animated widget.

Minimal example:

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

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

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

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


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

  @override
  void initState() {
    super.initState();

    Timer(Duration(milliseconds: 3000), (){
      if( mounted ) setState((){
        print('Enough splashing!');
        splash = false;
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    print('build   splash: $splash');

    return MaterialApp(
      title: 'FlutterTest',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: Scaffold(
        appBar: AppBar(
          title: Text('FlutterTest'),
        ),
        body: Center(
          child: splash
            ? Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                CircularProgressIndicator(strokeWidth: 1, valueColor: AlwaysStoppedAnimation<Color>(Colors.red)),
                Text('Splash...', style: TextStyle(color: Colors.red))
              ],
            )
            : Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                Text('FlutterTest', style: TextStyle(color: Colors.blue)),
              ],
            ),
        ),
      )
    );
  }
}

Result with CircularProgressIndicator present:

I/flutter (19306): build   splash: true
I/flutter (19306): Enough splashing!

Result without CircularProgressIndicator, or after "Hot Reload"/"Hot Refresh":

I/flutter (19436): build   splash: true
I/flutter (19436): Enough splashing!
I/flutter (19436): build   splash: false    

What is going on here?

I'm seeing this on an Android emulator in debug mode.

flutter doctor -v

[✓] Flutter (Channel stable, 1.20.3, on Mac OS X 10.15.1 19B88, locale en-SE)
    • Flutter version 1.20.3 at /Users/username/dev/flutter
    • Framework revision 216dee60c0 (5 weeks ago), 2020-09-01 12:24:47 -0700
    • Engine revision d1bc06f032
    • Dart version 2.9.2

 
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
    • Android SDK at /Users/username/Library/Android/sdk
    • Platform android-30, build-tools 30.0.2
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1136-b06)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 11.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 11.1, Build version 11A1027
    • CocoaPods version 1.8.4

[!] Android Studio (version 3.2)
    • Android Studio at /Applications/Android Studio.app/Contents
    ✗ Flutter plugin not installed; this adds Flutter specific functionality.
    ✗ Dart plugin not installed; this adds Dart specific functionality.
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1136-b06)

[✓] IntelliJ IDEA Community Edition (version 2018.3)
    • IntelliJ at /Applications/IntelliJ IDEA CE.app
    • Flutter plugin version 32.0.2
    • Dart plugin version 183.4733

[✓] Connected device (1 available)
    • sdk gphone x86 (mobile) • emulator-5554 • android-x86 • Android 11 (API 30) (emulator)

UPDATE

Tried it on another computer, and it worked. That computer had Flutter version 1.12.13+hotfix.8, so I tried updating Flutter to 1.22 on the computer where it didn't work. Still the same result. I checked the emulators - they were running the exact same API, system image, emulator version, and same HAXM version on both computers.

On the failing computer, I tried with a lower Android API - it worked. So I tried updating the system image revision for API 30 - still the same problem with a new AVD. As a last resort, I updated the emulator and HAXM to the latest revisions. Now it worked on API 30. So it seems the problem was somewhere in the emulator/HAXM, even though the exact same versions worked on another computer.