它是这样显示的。
Unhandled exception:
Bad state: Future already completed
#0 _AsyncCompleter.complete (dart:async/future_impl.dart:43:31)
#1 _NativeSocket.startConnect.<anonymous closure>.connectNext.<anonymous closure> (dart:io-patch/socket_patch.dart:678:23)
#2 _NativeSocket.issueWriteEvent.issue (dart:io-patch/socket_patch.dart:1043:14)
#3 _NativeSocket.issueWriteEvent (dart:io-patch/socket_patch.dart:1050:12)
#4 _NativeSocket.multiplex (dart:io-patch/socket_patch.dart:1071:11)
#5 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:168:12)
Error: Unable to 'pub upgrade' flutter tool. Retrying in five seconds...
我从 macOS Big Sur 完全卸载了 flutter。但它仍然显示相同的结果。