How to use Flutter to build an efficient and user-friendly mobile application?

Flutter development practical case: building efficient and user-friendly mobile applications.

Flutter, as an open source UI software development kit launched by Google, has quickly become a popular choice for developers due to its efficient development model and cross-platform features.

This article will take an in-depth look at how to build an efficient and user-friendly mobile application using the Flutter framework through an actual development case.

Project Overview.

We will build a simple accounting application where users can record daily income and expenses and generate monthly reports.

This application will include the following main functions: 1. User login/registration interface 2. The main interface displays today's income and expenses 3. Add a new record of income or expenditure 4. View history 5. Generate monthly reports

Environment construction.

First, make sure you have the Flutter SDK installed.

If not installed, you can visit [Flutter official website] (https://flutter.dev/) to download and install.

After the installation is complete, run the following command to create a new Flutter project:

flutter create finance_app
cd finance_app

User login/registration interface.

We will use flutter_blocLibrary to manage the status of user authentication.

First, add a dependency in the pubspec.yaml file:

dependencies:
  flutter:
    sdk: flutter
  flutter_bloc: ^7.0.0
  firebase_auth: ^3.0.0
  google_sign_in: ^5.0.0

Then, create a Bloc to handle user authentication logic.

Create a new one in the lib directory authFolder and create in it auth_bloc.dartFile:

dart
// lib/auth/auth_bloc.dart
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:google_sign_in/google_sign_in.dart';

part 'auth_event.dart';
part 'auth_state.dart';

class AuthBloc extends Bloc {
  final FirebaseAuth _firebaseAuth = FirebaseAuth.instance;
  final GoogleSignIn _googleSignIn = GoogleSignIn();

  AuthBloc() : super(AuthInitial()) {
    on((event, emit) async {
      if (event is AuthLoggedInRequested) {
        try {
          final GoogleSignInAccount? googleUser = await _googleSignIn.signIn();
          final GoogleSignInAuthentication? googleAuth = await googleUser?.authentication;

          final credential = GoogleAuthProvider.credential(
            accessToken: googleAuth?.accessToken,
            idToken: googleAuth?.idToken,
          );

          await _firebaseAuth.signInWithCredential(credential);
          emit(AuthLoggedIn());
        } catch (e) {
          emit(AuthLoggedOut());
          print(e);
        }
      } else if (event is AuthLoggedOutRequested) {
        await _googleSignIn.signOut();
        await _firebaseAuth.signOut();
        emit(AuthLoggedOut());
      }
    });
  }
}

Next, create an event and status file:

dart
// lib/auth/auth_event.dart
part of 'auth_bloc.dart';

abstract class AuthEvent {}

class AuthLoggedInRequested extends AuthEvent {}

class AuthLoggedOutRequested extends AuthEvent {}

dart
// lib/auth/auth_state.dart
part of 'auth_bloc.dart';

abstract class AuthState {}

class AuthInitial extends AuthState {}

class AuthLoggedIn extends AuthState {}

class AuthLoggedOut extends AuthState {}

Finally, use this Bloc in the main file:

dart
// lib/main.dart
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:finance_app/auth/auth_bloc.dart';
import 'package:finance_app/screens/home_screen.dart';
import 'package:finance_app/screens/login_screen.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MultiBlocProvider(
      providers: [
        BlocProvider(create: (context) => AuthBloc()),
      ],
      child: MaterialApp(
        title: 'Finance App',
        theme: ThemeData(primarySwatch: Colors.blue),
        home: BlocBuilder(
          builder: (context, state) {
            if (state is AuthLoggedIn) {
              return HomeScreen();
            } else {
              return LoginScreen();
            }
          },
        ),
      ),
    );
  }
}

The main interface displays today's income and expenses.

We will use flutter_blocTo manage the state of the application.

First, add a dependency in the pubspec.yaml file:

dependencies:
  flutter:
    sdk: flutter
  flutter_bloc: ^7.0.0
  equatable: ^2.0.0

Then, create a Bloc to handle the state of the application.

Create a new one in the lib directory appFolder and create in it app_bloc.dartFile:

dart
// lib/app/app_bloc.dart
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:equatable/equatable.dart';

part 'app_event.dart';
part 'app_state.dart';

class AppBloc extends Bloc {
  AppBloc() : super(AppInitial()) {
    on((event, emit) {});
  }
}

Next, create an event and status file:

dart
// lib/app/app_event.dart
part of 'app_bloc.dart';

abstract class AppEvent extends Equatable {}

class AppInitialized extends AppEvent {
  @override
  List

dart
// lib/app/app_state.dart
part of 'app_bloc.dart';

abstract class AppState extends Equatable {}

class AppInitial extends AppState {
  @override
  List

Finally, use this Bloc in the main file:

dart
// lib/main.dart
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:finance_app/app/app_bloc.dart';
import 'package:finance_app/screens/home_screen.dart';
import 'package:finance_app/screens/login_screen.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MultiBlocProvider(
      providers: [
        BlocProvider(create: (context) => AppBloc()),
      ],
      child: MaterialApp(
        title: 'Finance App',
        theme: ThemeData(primarySwatch: Colors.blue),
        home: BlocBuilder(
          builder: (context, state) {
            if (state is AppInitialized) {
              return HomeScreen();
            } else {
              return LoginScreen();
            }
          },
        ),
      ),
    );
  }
}

Add a new record of income or expenses.

We will use flutter_blocTo manage the status of adding records.

First, add a dependency in the pubspec.yaml file:

dependencies:
  flutter:
    sdk: flutter
  flutter_bloc: ^7.0.0
  equatable: ^2.0.0