flutter 中的 Firebase 初始化和导航问题

Question

我正在用 flutter 开发一个移动应用程序。我的应用程序应该仅在有互联网连接时运行，因为它使用 Firebase 作为数据库。

我在主函数中初始化 Firebase。但是，当用户在没有互联网连接的情况下启动时，我会显示一个对话框，当用户连接到互联网时，我会启动导航到下一个屏幕的相同过程和过程。

但是，导航在正常流程中顺利进行，但在用户到达启动后连接到互联网的其他流程中。即使所有函数调用都正确执行，导航也没有发生。我已经检查过日志记录。

我当前的启动屏幕及其视图模型的实现如下。我已经尝试了所有记录但无法锻炼。谁能告诉我我做错了什么以及需要修复什么？

启动画面：

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import '../View Models/Splash View Model.dart';
import 'Signup Screen.dart'; // Replace with actual path to signup screen

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

  @override
  Widget build(BuildContext context) {
    final viewModel = Provider.of<SplashViewModel>(context, listen: false);

    WidgetsBinding.instance.addPostFrameCallback((_) {
      _initializeApp(context, viewModel ,false);
    });

    return Scaffold(
      body: Container(
        decoration: const BoxDecoration(
          image: DecorationImage(
            image: AssetImage('assets/drawables_png/splash_bg.png'),
            fit: BoxFit.cover,
          ),
        ),
        child: Column(
          children: [
            Expanded(
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  Image.asset(
                    'assets/drawables_png/splash_ic.png',
                    width: 150,
                    height: 150,
                  ),
                  const SizedBox(height: 20),
                  const Text(
                    'EASY FOOD JOURNAL',
                    style: TextStyle(
                      fontFamily: 'Viga',
                      fontSize: 24,
                      color: Colors.white,
                    ),
                  ),
                  const SizedBox(height: 10),
                  const Text(
                    'Effortless Tracking for Delicious Living!',
                    style: TextStyle(
                      fontFamily: 'Outfit',
                      fontSize: 16,
                      color: Colors.white,
                    ),
                  ),
                  const SizedBox(height: 40),
                ],
              ),
            ),
            Padding(
              padding: const EdgeInsets.symmetric(horizontal: 60.0, vertical: 30),
              child: Consumer<SplashViewModel>(
                builder: (context, viewModel, child) {
                  return LinearProgressIndicator(
                    value: viewModel.progress,
                    backgroundColor: const Color(0xff29ffffff),
                    valueColor: const AlwaysStoppedAnimation<Color>(Colors.white),
                  );
                },
              ),
            ),
          ],
        ),
      ),
    );
  }

  void _initializeApp(BuildContext context, SplashViewModel viewModel , bool callFirebase) async {
    print("finally here011");
    bool connected = await viewModel.checkInternetConnection();

    if (connected) {
      bool firebaseInitialized = await viewModel.initializeFirebase(callFirebase);
      if (firebaseInitialized) {
        print("finally here211");
        await viewModel.startProgress();
        print("finally here311");
        _navigateBasedOnLoginStatus(context, viewModel);
        print("finally here411");
      } else {
        _showNoConnectionDialog(context, viewModel);
      }
    } else {
      _showNoConnectionDialog(context, viewModel);
    }
  }

  void _showNoConnectionDialog(BuildContext context, SplashViewModel viewModel) {
    showDialog(
      context: context,
      barrierDismissible: false,
      builder: (BuildContext context) {
        return AlertDialog(
          title: const Text("No Internet Connection"),
          content: const Text("Please connect to the internet to continue."),
          actions: [
            TextButton(
              child: const Text("Retry"),
              onPressed: () {
                Navigator.of(context).pop();
                _initializeApp(context, viewModel , true); // Retry the initialization
              },
            ),
          ],
        );
      },
    );
  }

  void _navigateBasedOnLoginStatus(BuildContext context, SplashViewModel viewModel) async {
    bool isLoggedIn = await viewModel.isUserLoggedIn();

    // Use addPostFrameCallback to ensure context is valid for navigation
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (isLoggedIn) {

        Navigator.pushReplacement(
          context,
          MaterialPageRoute(builder: (_) => const SignupScreen()), // Change to home screen if logged in
        );
      } else {
        Navigator.pushReplacement(
          context,
          MaterialPageRoute(builder: (_) => const SignupScreen()), // Change to signup screen if not logged in
        );
      }
    });
  }
}

查看模型：

import 'dart:async';

import 'package:connectivity_plus/connectivity_plus.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/cupertino.dart';

import '../Utils/SharedPrefs.dart';
class SplashViewModel with ChangeNotifier {
  double _progress = 0.0;
  Timer? _timer;

  double get progress => _progress;

  /// Initializes Firebase separately to control when it is called.
  Future<bool> initializeFirebase( bool callFirebase) async {
    try {
      if(callFirebase){
        if (Firebase.apps.isEmpty) {
          await Firebase.initializeApp();
        }

      }
      return true;
    } catch (e) {
      print("Firebase initialization failed: $e");
      return false;
    }
  }

  /// Starts the progress bar animation.
  Future<void> startProgress() async {
    _resetProgress();

    // Start progress bar animation
    _timer = Timer.periodic(const Duration(milliseconds: 50), (timer) {
      if (_progress < 1.0) {
        _progress += 0.02; // Increment progress by 2%
        notifyListeners();
      } else {
        timer.cancel();
      }
    });

    // Complete progress after 2 seconds for animation consistency
    if (Firebase.apps.length != 0) {
      await Future.delayed(const Duration(seconds: 2));
      _progress = 1.0;
      notifyListeners();
      _timer?.cancel();
    }
  }

  void _resetProgress() {
    _progress = 0.0;
    notifyListeners();
    _timer?.cancel();
  }

  Future<bool> checkInternetConnection() async {
    var connectivityResult = await Connectivity().checkConnectivity();
    return connectivityResult != ConnectivityResult.none;
  }

  Future<bool> isUserLoggedIn() async {
    User? currentUser = FirebaseAuth.instance.currentUser;
    if (currentUser == null) return false;

    bool onboardingComplete = await SharedPreferencesUtil.getValue<bool>('onboarding_complete', false);
    return onboardingComplete;
  }

  @override
  void dispose() {
    _timer?.cancel();
    super.dispose();
  }
}

Answer 1

问题似乎出在 checkInternetConnection 上，它仅被调用一次，因此应用程序不会对连接更改做出反应。