flutter - 错误 :flutter/lib/ui/ui_dart_state. cc(199) 未处理的异常:对空值使用空检查运算符

Question

我正在尝试通过可注入(inject)生成，我做了 flutter clean 也行不通，我使用的是稳定版本的 flutter 2.2.2，我在这行代码上遇到了空检查错误
此代码抛出错误

SharedPreferences.getInstance();

还有这个代码

   @module
    abstract class ThemeModule {
      @preResolve
      Future<SharedPreferences> get prefs async =>
           await SharedPreferences.getInstance();
    }

错误堆栈

E/flutter (27063): [ERROR:flutter/lib/ui/ui_dart_state.cc(199)] Unhandled Exception: Null check operator used on a null value
E/flutter (27063): #0      MethodChannel.binaryMessenger
package:flutter/…/services/platform_channel.dart:142
E/flutter (27063): #1      MethodChannel._invokeMethod
package:flutter/…/services/platform_channel.dart:148
E/flutter (27063): #2      MethodChannel.invokeMethod
package:flutter/…/services/platform_channel.dart:331
E/flutter (27063): #3      MethodChannel.invokeMapMethod
package:flutter/…/services/platform_channel.dart:358
E/flutter (27063): #4      MethodChannelSharedPreferencesStore.getAll
package:shared_preferences_platform_interface/method_channel_shared_preferences.dart:44
E/flutter (27063): #5      SharedPreferences._getSharedPreferencesMap
package:shared_preferences/shared_preferences.dart:180
E/flutter (27063): #6      SharedPreferences.getInstance
package:shared_preferences/shared_preferences.dart:56
E/flutter (27063): #7      main
package:financial/main.dart:12
E/flutter (27063): #8      _runMainZoned.<anonymous closure>.<anonymous closure> (dart:ui/hooks.dart:142:25)
E/flutter (27063): #9      _rootRun (dart:async/zone.dart:1354:13)
E/flutter (27063): #10     _CustomZone.run (dart:async/zone.dart:1258:19)
E/flutter (27063): #11     _runZoned (dart:async/zone.dart:1789:10)
E/flutter (27063): #12     runZonedGuarded (dart:async/zone.dart:1777:12)
E/flutter (27063): #13     _runMainZoned.<anonymous closure> (dart:ui/hooks.dart:138:5)
E/flutter (27063): #14     _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:283:19)
E/flutter (27063): #15     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)

Answer 1

我有同样的问题，解决方案是添加 WidgetsFlutterBinding.ensureInitialized()在运行应用程序之前的主要功能中:

Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized();
// init your dependency injection here
runApp(MyApp());}

来自 docs :
返回 WidgetsBinding 的一个实例，必要时创建并初始化它。如果创建了一个，
它将是一个 WidgetsFlutterBinding。如果之前已初始化，那么它至少会实现 WidgetsBinding。
如果您需要在调用 runApp 之前初始化绑定(bind)，则只需调用此方法。