Flutter & Dart Notes

April 13, 2026

Commands, routing, state management, and language patterns

Flutter & Dart

Flutter

Commands

bash

flutter doctor
 
flutter clean ios -> flutter pub get
 
flutter clean android -> flutter pub get
 
flutter pub add <package_name>
 
flutter pub outdated # To see which dependencies have newer versions available

Configure Firebase

bash

flutter pub add <firebase_packages>
 
dart pub global activate flutterfire_cli # Remember to add to OS env-path: C:\Users\$USERNAME\AppData\Local\Pub\Cache\bin

Flutter Devtool

scrcpy ↗ # Remember to add to OS env-path

Flutter pubspec.yaml

yaml

assets:
  - assets/graphics/
 
fonts:
  - family: Poppins
    fonts:
      - asset: assets/fonts/Poppins-Medium.ttf
        weight: 400

Flutter Routing

dart

import 'package:flutter/material.dart';
import 'package:flutter_testing/world_time/pages/home.dart';
import 'package:flutter_testing/world_time/pages/choose_location.dart';
import 'package:flutter_testing/world_time/pages/loading.dart';
 
void main() => runApp(MaterialApp(
      initialRoute: '/', // Remove later on, for testing purposes
      routes: {
        '/': (context) => const Loading(),
        '/home': (context) => const Home(),
        '/location': (context) => const ChooseLocation()
      },
    ));

Pushing Routes

dart

Navigator.pushReplacementNamed(context, '/home');
Navigator.pushNamed(context, '/home');

Sending Arguments to a Route

dart

class _LoadingState extends State<Loading> {
  void setupWorldTime() async {
    WorldTime berlin = WorldTime(
        locationName: "Berlin",
        flagIconPath: "germany.png",
        timezoneEndpoint: "Europe/Berlin");
    await berlin.getTime();
    Navigator.pushReplacementNamed(context, '/home', arguments: {
      'location': berlin.locationName,
      'flag': berlin.flagIconPath,
      'time': berlin.time
    });
  }
 
  @override
  void initState() {
    super.initState();
    setupWorldTime();
  }
....
 
class _HomeState extends State<Home> {
  Map data = {};
 
  @override
  Widget build(BuildContext context) {
    data = ModalRoute.of(context)!.settings.arguments as Map;
    ....
....

Dart

String Interpolation

dart

_selectedIndex = 0;
print('${_selectedIndex}'); // Automatically calls the toString() method on _selectedIndex
print(_selectedIndex.toString()); // The same as above

setState

Only Stateful Widgets can usesetState((){})

Use setState to trigger the build function of a statefull widget:

dart

setState(() {
  age += 1;
});

Stateful widgets have lifecycle methods we can tap into:

initState()
The first method to be called once our state object has been created, is only called once, when the widget has first been created.

dart

@override
void initState() {
  //TODO: Implement initstate
  super.initState();
}

Build()
Builds the widget tree, is triggered everytime we usesetState
Dispose()
When the widget or state object is removed.

Null Coalescing and More

variableWhichMMayBeNull ?? variableWhichMayAlsoBeNull ?? variableWhichMayAgainBeNull

prop = objectPropDrillingWherePropertyMayBeNull?.stringPropertyThatMayBeNull

dart

String name;
name ??= "Adam"; // name is null and "Adam" is assigned to name
print(name); //-> Adam
name ??= "Adrian"; // name is not null and "Adrian" is hence not assigned to name
print(name); //-> Adam

Factory Constructors

dart

class Cat {
  final String name;
  Cat(this.name);
  factory Cat.fluffball() {
    return Cat('Fluff Ball');
  }
}
 
void test() {
  final fluffBall = Cat.fluffBall();
  print(fluffBall.name);
}

Custom Operators

dart

class Cat extends Object {
  final String name;
  Cat(this.name);
 
  @override
  bool operator ==(covariant Cat other) => other.name == name;
 
  @override
  int get hashCode => name.hashCode;
}

Extensions

dart

extension Run on Cat {
  void run() {
    print('Cat $name is running');
  }
}
 
void test() {
  final meow = Cat('Fluffers');
  meow.run();
}

Getter Extension

dart

class Person {
  final String firstName;
  final String lastName;
  Person(this.firstName, this.lastName);
}
 
extension FullName on Person {
  String get fullName => '$firstName $lastName';
}
 
void test() {
  final foo = Person('Foo', 'Bar');
  print(foo.fullName);
}

Futures

dart

Future<int> aFutureFunction(int a) {
  return Future.delayed(const Duration(seconds: 3), () => a * 2);
}
 
void test() async {
  final result = await aFutureFunction(8);
  print(result); // prints 16 after 3 seconds.
}

Await Example

dart

void getData() async {
  late String username;
  await Future.delayed(Duration(seconds: 3), () {
    username = "Dirk";
  });
  Future.delayed(Duration(seconds: 3), () {
    print("$username is a developer and musician!");
  });
  print("End of function")
  //> End of function
  //> Dirk is a developer and musician!
}

Streams

dart

Stream<String> getName() {
  return Stream.value('Foo');
}
 
void test() async {
  await for (final value in getName()) {
    print(value);
  }
  print('Stream finished working);
}

dart

Stream<String> getName() {
  return Stream.periodic(const Duration(seconds: 1), (value) {
    return 'Foo';
  });
}
 
void test() async {
  await for (final value in getName()) {
    print(value);
  }
}

Generators

Async

dart

Stream<Iterable<int>> getOneTwoThree() async* {
  ...
}

Sync

dart

Iterable<int> getOneTwoThree() sync* {
  yield 1;
  yield 2;
  yield 3;
}
 
void test() {
  for (final value in getOneTwoThree()) {
    print(value);
  }
  // Or: print(getOneTwoThree());
}

Generics

dart

class PairOfIntegers {
  final int value1;
  final int value2;
  PairOfIntegers(this.value1, this.value2);
}
 
class Pair<A, B> {
  final A value1;
  final B value2;
  Pair(this.value1, this.value2);
}
 
void test() {
  final names = Pair('Foo', 'Bar');
  final ages = Pair(22, 34);
}