Useful or not, from you.
flutter Flutter ImagePicker Plugin (No implementation found for method pickImage)

MissingPluginException(No implementation found for method pickImage on channel plugins.flutter.io/image_picker)

E/flutter ( 8747): [ERROR:topaz/lib/tonic/logging/dart_error.cc(16)] Unhandled exception:
E/flutter ( 8747): MissingPluginException(No implementation found for method pickImage on channel plugins.flutter.io/image_picker)
E/flutter ( 8747): #0      MethodChannel.invokeMethod (package:flutter/src/services/platform_channel.dart:278:7)
E/flutter ( 8747): <asynchronous suspension>
E/flutter ( 8747): #1      ImagePicker.pickImage (package:image_picker/image_picker.dart:47:40)
E/flutter ( 8747): <asynchronous suspension>
E/flutter ( 8747): #2      _HomeState.getImage (package:sensegrass/screens/home.dart:20:35)
E/flutter ( 8747): <asynchronous suspension>
E/flutter ( 8747): #3      _HomeState.build.<anonymous closure> (package:sensegrass/screens/home.dart:85:11)
E/flutter ( 8747): #4      _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:494:14)
E/flutter ( 8747): #5      _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:549:30)
E/flutter ( 8747): #6      GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:102:24)
E/flutter ( 8747): #7      TapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:161:9)
E/flutter ( 8747): #8      TapGestureRecognizer.handlePrimaryPointer (package:flutter/src/gestures/tap.dart:94:7)
E/flutter ( 8747): #9      PrimaryPointerGestureRecognizer.handleEvent (package:flutter/src/gestures/recognizer.dart:315:9)
E/flutter ( 8747): #10     PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:73:12)
E/flutter ( 8747): #11     PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:101:11)
E/flutter ( 8747): #12     _WidgetsFlutterBinding&BindingBase&GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:143:19)
E/flutter ( 8747): #13     _WidgetsFlutterBinding&BindingBase&GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:121:22)
E/flutter ( 8747): #14     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:101:7)
E/flutter ( 8747): #15     _WidgetsFlutterBinding&BindingBase&GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:64:7)
E/flutter ( 8747): #16     _WidgetsFlutterBinding&BindingBase&GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:48:7)
E/flutter ( 8747): #17     _invoke1 (dart:ui/hooks.dart:134:13)
E/flutter ( 8747): #18     _dispatchPointerDataPacket (dart:ui/hooks.dart:91:5)

That's a useful answer
Without any help

flutter clean solves the problem indeed. But often leads another error.