@immutable class complaint

[robertgao2023]

As a newbie I was trying to test drive the Flutter-Basics. I was wondering, this sample code could run on all supported platforms? Or it only runs on certain platforms?

So far I have tried it on an android-x64 emulator, and chrome platform and here is what I encountered:
I am getting following problems and was wondering if you can help me by pointing to the right direction:

1. running on Chrome, the output showing:
   [Running] dart "c:\Users\rober\MyDevSandBox\Flutter-Basics\lib\main.dart"
   ../my-flutter-app/flutter/packages/flutter/lib/src/material/animated_icons.dart:9:8: Error: Dart library 'dart:ui' is not available on this platform.
   import 'dart:ui' as ui show Canvas, Paint, Path, lerpDouble;
   ^
   Context: The unavailable library 'dart:ui' is imported through these packages:

   package:fitness => package:flutter => dart:ui

2. On both platforms tested, the Problem window showing:
   [{
   "resource": "/C:/Users/rober/MyDevSandBox/Flutter-Basics/lib/pages/home.dart",
   "owner": "generated_diagnostic_collection_name@immutable class complaint #1",
   "code": {
   "value": "must_be_immutable",
   "target": {
   "$mid": 1,
   "path": "/diagnostics/must_be_immutable",
   "scheme": "https",
   "authority": "dart.dev"
   }
   },
   "severity": 4,
   "message": "This class (or a class that this class inherits from) is marked as '@immutable', but one or more of its instance fields aren't final: HomePage.categories, HomePage.diets, HomePage.popularDiets",
   "source": "dart",
   "startLineNumber": 7,
   "startColumn": 7,
   "endLineNumber": 7,
   "endColumn": 15
   }]

Please help, Thanks...