Question

运行这个

import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';

void main() async {
   await Firebase.initializeApp();
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: ThePage(),
    );
  }
}

class ThePage extends StatelessWidget {
  const ThePage({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(          
    );
  }
}

给出用于空值的空检查运算符并指出行 Firebase.initializeApp()。我也试过 flutter clean。

以及堆栈跟踪中的错误

E/flutter (31894): [ERROR:flutter/lib/ui/ui_dart_state.cc(199)] Unhandled Exception: Null check operator used on a null value
E/flutter (31894): #0      MethodChannel.binaryMessenger
package:flutter/…/services/platform_channel.dart:142
E/flutter (31894): #1      MethodChannel._invokeMethod
package:flutter/…/services/platform_channel.dart:148
E/flutter (31894): #2      MethodChannel.invokeMethod
package:flutter/…/services/platform_channel.dart:331
E/flutter (31894): #3      MethodChannel.invokeListMethod
package:flutter/…/services/platform_channel.dart:344
E/flutter (31894): #4      MethodChannelFirebase._initializeCore
package:firebase_core_platform_interface/…/method_channel/method_channel_firebase.dart:30
E/flutter (31894): #5      MethodChannelFirebase.initializeApp
package:firebase_core_platform_interface/…/method_channel/method_channel_firebase.dart:77
E/flutter (31894): #6      Firebase.initializeApp
package:firebase_core/src/firebase.dart:41
E/flutter (31894): #7      main
package:firebasetests/main.dart:5
E/flutter (31894): #8      _runMainZoned.<anonymous closure>.<anonymous closure> (dart:ui/hooks.dart:142:25)
E/flutter (31894): #9      _rootRun (dart:async/zone.dart:1354:13)
E/flutter (31894): #10     _CustomZone.run (dart:async/zone.dart:1258:19)
E/flutter (31894): #11     _runZoned (dart:async/zone.dart:1789:10)
E/flutter (31894): #12     runZonedGuarded (dart:async/zone.dart:1777:12)
E/flutter (31894): #13     _runMainZoned.<anonymous closure> (dart:ui/hooks.dart:138:5)
E/flutter (31894): #14     _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:283:19)
E/flutter (31894): #15     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)

这是错误的堆栈跟踪，在主程序中删除 Firebase.initializeApp() 后，它运行良好。

Answer 1

您应该在主函数中添加 WidgetsFlutterBinding.ensureInitialized();：

void main() async {
  WidgetsFlutterBinding.ensureInitialized(); // Add this

  await Firebase.initializeApp();
  runApp(MyApp());
}

对于 Firebase 初始化，需要使用 Flutter Platform Channels 访问本机代码。为此，您需要确保 Flutter 引擎绑定已初始化。

Answer 2

使用@mkobuolys 提到的代码行。

我在 Visual Studio Code 中遇到了同样的问题，但它没有显示任何有关错误的详细信息，但 Android Studio 显示了。

如果有人感兴趣，这里是异常消息中最重要的信息：

<块引用>

如果您正在运行应用程序并且需要访问二进制文件已调用 runApp() 之前的信使（例如，在插件初始化），那么你需要显式调用 WidgetsFlutterBinding.ensureInitialized() 首先。如果你正在运行一个测试，您可以调用 TestWidgetsFlutterBinding.ensureInitialized() 作为测试的 main() 方法中的第一行来初始化绑定。

firebase.initialiseapp() 给出错误：用于空值的空检查运算符

2 个答案: