Running in Android device,back button seem have some problems.

[SunLongbri]

Running in Android device,in scan screen,when I click back button in android device,console have some debug .this is:
W/WindowDecorActionBar(17795): should not do the transition or the transition anim is null or it is running or the mContainer view is null or mContainer view hasn't been drawn to screen
I/HwResourcesImpl(17795): load icon id : 7f0c0000, pkgName : com.morimatsu.imes_report
W/CfgFilePolicy(17795): No config file found for:xml/hw_launcher_load_icon.xml
W/CfgFilePolicy(17795): CFG_DIRS length : 11
E/HwResourcesImpl(17795): readDefaultConfig : FileNotFoundException
W/CfgFilePolicy(17795): No config file found for:/themes/diff/icons
W/CfgFilePolicy(17795): CFG_DIRS length : 11
I/HwResourcesImpl(17795): icon : com.morimatsu.imes_report found in app
I/HwCust (17795): Constructor found for class android.content.res.HwCustHwResourcesImpl
I/HwPointEventFilter(17795): do not support AFT because of no config
E/Camera (17795): Camera new cameraInitNormal:0
I/art (17795): Do partial code cache collection, code=31KB, data=24KB
I/art (17795): After code cache collection, code=25KB, data=21KB
I/art (17795): Increasing code cache capacity to 128KB
E/flutter (17795): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: FormatException: Invalid envelope
E/flutter (17795): #0 StandardMethodCodec.decodeEnvelope (package:flutter/src/services/message_codecs.dart:566:7)
E/flutter (17795): #1 MethodChannel.invokeMethod (package:flutter/src/services/platform_channel.dart:316:33)
E/flutter (17795):
E/flutter (17795): #2 BarcodeScanner.scan (package:barcode_scan/barcode_scan.dart:9:56)
E/flutter (17795):
E/flutter (17795): #3 startScan (package:imes_report/widget/barcode_scan.dart:7:41)
E/flutter (17795): #4 _AsyncAwaitCompleter.start (dart:async-patch/async_patch.dart:49:6)
E/flutter (17795): #5 startScan (package:imes_report/widget/barcode_scan.dart:5:17)
E/flutter (17795): #6 _AddWeldPageState._initData. (package:imes_report/pages/add_weld_page.dart:87:11)
E/flutter (17795): #7 _AsyncAwaitCompleter.start (dart:async-patch/async_patch.dart:49:6)
E/flutter (17795): #8 _AddWeldPageState._initData. (package:imes_report/pages/add_weld_page.dart:84:24)
E/flutter (17795): #9 _rootRunUnary (dart:async/zone.dart:1132:38)
E/flutter (17795): #10 _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter (17795): #11 _FutureListener.handleValue (dart:async/future_impl.dart:126:18)
E/flutter (17795): #12 Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:639:45)
E/flutter (17795): #13 Future._propagateToListeners (dart:async/future_impl.dart:668:32)
E/flutter (17795): #14 Future._complete (dart:async/future_impl.dart:473:7)
E/flutter (17795): #15 _SyncCompleter.complete (dart:async/future_impl.dart:51:12)
E/flutter (17795): #16 _AsyncAwaitCompleter.complete (dart:async-patch/async_patch.dart:28:18)
E/flutter (17795): #17 _completeOnAsyncReturn (dart:async-patch/async_patch.dart:294:13)
E/flutter (17795): #18 DatabaseHelper.getCount (package:imes_report/db/database_helper.dart)
E/flutter (17795): #19 _asyncThenWrapperHelper. (dart:async-patch/async_patch.dart:77:64)
E/flutter (17795): #20 _rootRunUnary (dart:async/zone.dart:1132:38)
E/flutter (17795): #21 _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter (17795): #22 _FutureListener.handleValue (dart:async/future_impl.dart:126:18)
E/flutter (17795): #23 Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:639:45)
E/flutter (17795): #24 Future._propagateToListeners (dart:async/future_impl.dart:668:32)
E/flutter (17795): #25 Future._complete (dart:async/future_impl.dart:473:7)
E/flutter (17795): #26 _SyncCompleter.complete (dart:async/future_impl.dart:51:12)
E/flutter (17795): #27 _AsyncAwaitCompleter.complete (dart:async-patch/async_patch.dart:28:18)
E/flutter (17795): #28 _completeOnAsyncReturn (dart:async-patch/async_patch.dart:294:13)
E/flutter (17795): #29 _SqfliteDatabaseBase&Object&SqfliteDatabaseMixin.txnSynchronized (package:sqflite/src/database_mixin.dart)
E/flutter (17795): #30 _asyncThenWrapperHelper. (dart:async-patch/async_patch.dart:77:64)
E/flutter (17795): #31 _rootRunUnary (dart:async/zone.dart:1132:38)
E/flutter (17795): #32 _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter (17795): #33 _FutureListener.handleValue (dart:async/future_impl.dart:126:18)
E/flutter (17795): #34 Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:639:45)
E/flutter (17795): #35 Future._propagateToListeners (dart:async/future_impl.dart:668:32)
E/flutter (17795): #36 Future._complete (dart:async/future_impl.dart:473:7)
E/flutter (17795): #37 _SyncCompleter.complete (dart:async/future_impl.dart:51:12)
E/flutter (17795): #38 _AsyncAwaitCompleter.complete (dart:async-patch/async_patch.dart:28:18)
E/flutter (17795): #39 _completeOnAsyncReturn (dart:async-patch/async_patch.dart:294:13)
E/flutter (17795): #40 BasicLock.synchronized (package:synchronized/src/basic_lock.dart)
E/flutter (17795): #41 _asyncThenWrapperHelper. (dart:async-patch/async_patch.dart:77:64)
E/flutter (17795): #42 _rootRunUnary (dart:async/zone.dart:1132:38)
E/flutter (17795): #43 _CustomZone.runUnary (dart:async/zone.dart:1029:19)
E/flutter (17795): #44 _FutureListener.handleValue (dart:async/future_impl.dart:126:18)
E/flutter (17795): #45 Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:639:45)
E/flutter (17795): #46 Future._propagateToListeners (dart:async/future_impl.dart:668:32)
E/flutter (17795): #47 Future._complete (dart:async/future_impl.dart:473:7)
E/flutter (17795): #48 _SyncCompleter.complete (dart:async/future_impl.dart:51:12)
E/flutter (17795): #49 _AsyncAwaitCompleter.complete (dart:async-patch/async_patch.dart:28:18)
E/flutter (17795): #50 _completeOnAsyncReturn (dart:async-patch/async_patch.dart:294:13)
E/flutter (17795): #51 _SqfliteDatabaseBase&O

I want click back button ,and return previous page ,can you give me some advice?