flutter 集成极光推送的时候 setup找不到方法
```
[ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: MissingPluginException(No implementation found for method setup on channel jpush)
E/flutter (10734): #0 MethodChannel.invokeMethod (package:flutter/src/services/platform_channel.dart:300:7)
E/flutter (10734):
E/flutter (10734): #1 JPush.setup (package:jpush_flutter/jpush_flutter.dart:34:16)
E/flutter (10734): #2 MyAppState.initState (package:flutter_app2/main.dart:30:13)
E/flutter (10734): #3 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3846:58)
E/flutter (10734): #4 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3717:5)
E/flutter (10734): #5 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2961:14)
E/flutter (10734): #6 Element.updateChild (package:flutter/src/widgets/framework.dart:2764:12)
E/flutter (10734): #7 RenderObjectToWidgetElement._rebuild (package:flutter/src/widgets/binding.dart:933:16)
E/flutter (10734): #8 RenderObjectToWidgetElement.mount (package:flutter/src/widgets/binding.dart:904:5)
E/flutter (10734): #9 RenderObjectToWidgetAdapter.attachToRenderTree. (package:flutter/src/widgets/binding.dart:850:17)
E/flutter (10734): #10 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2258:19)
E/flutter (10734): #11 RenderObjectToWidgetAdapter.attachToRenderTree (package:flutter/src/widgets/binding.dart:849:13)
E/flutter (10734): #12 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.attachRootWidget (package:flutter/src/widgets/binding.dart:736:7)
E/flutter (10734): #13 runApp (package:flutter/src/widgets/binding.dart:780:7)
E/flutter (10734): #14 main (package:flutter_app2/main.dart:6:16)
E/flutter (10734): #15 _runMainZoned.. (dart:ui/hooks.dart:199:25)
E/flutter (10734): #16 _rootRun (dart:async/zone.dart:1124:13)
E/flutter (10734): #17 _CustomZone.run (dart:async/zone.dart:1021:19)
E/flutter (10734): #18 _runZoned (dart:async/zone.dart:1516:10)
E/flutter (10734): #19 runZoned (dart:async/zone.dart:1500:12)
E/flutter (10734): #20 _runMainZoned. (dart:ui/hooks.dart:190:5)
E/flutter (10734): #21 _startIsolate. (dart:isolate-patch/isolate_patch.dart:300:19)
E/flutter (10734): #22 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:171:12)