I just started learning Flutter and during the development, the app got stuck at Performing hot-reload.

I tried flutter clean, flutter pub get and reboot of the android emulator and then re-run the app. Now the app is stuck at Connecting to VM service.

After undoing my changes, it got resolved. So I traced my changes line by line and found that my incomplete code that returned an empty Container from ListView builder’s callback is causing it. I could reproduce it in a clean project as follow:

import 'package:flutter/material.dart';

void main() {
  runApp(const MainApp());
}

class MainApp extends StatelessWidget {
  const MainApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
          body: Padding(
              padding: EdgeInsets.all(1),
              child: ListView.builder(itemBuilder: (context, index) {
                return Container();
              }))),
    );
  }
}

Why does this happen? My guess is that it needs to return a Widget or a tree of Widgets that finally resolves to a Render Widget. But then, shouldn’t it be somehow warned or errored if I cannot return Widgets that don’t resolve to a Render Widget?

I have tried searching the existing Flutter issues and didn’t find it.