Can't open xls file

[tbm98]

When I open xls file. It show Unhandled Exception: FormatException: Could not find End of Central Directory Record

E/flutter (15982): #0      ZipDirectory._findSignature (package:archive/src/zip/zip_directory.dart:149:5)
E/flutter (15982): #1      new ZipDirectory.read (package:archive/src/zip/zip_directory.dart:28:20)
E/flutter (15982): #2      ZipDecoder.decodeBuffer (package:archive/src/zip_decoder.dart:21:30)
E/flutter (15982): #3      ZipDecoder.decodeBytes (package:archive/src/zip_decoder.dart:15:12)
E/flutter (15982): #4      new SpreadsheetDecoder.decodeBytes (package:spreadsheet_decoder/src/spreadsheet.dart:75:32)
E/flutter (15982): #5      _LoginPageState.readData (package:studentsocialgooglecalendar/login_page.dart:27:38)
E/flutter (15982): #6      _LoginPageState.readFileSync (package:studentsocialgooglecalendar/login_page.dart:20:5)
E/flutter (15982): <asynchronous suspension>
E/flutter (15982): #7      _LoginPageState.build.<anonymous closure> (package:studentsocialgooglecalendar/login_page.dart:58:11)
E/flutter (15982): #8      _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:706:14)
E/flutter (15982): #9      _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:789:36)
E/flutter (15982): #10     GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:182:24)
E/flutter (15982): #11     TapGestureRecognizer.handleTapUp (package:flutter/src/gestures/tap.dart:486:11)
E/flutter (15982): #12     BaseTapGestureRecognizer._checkUp (package:flutter/src/gestures/tap.dart:264:5)
E/flutter (15982): #13     BaseTapGestureRecognizer.handlePrimaryPointer (package:flutter/src/gestures/tap.dart:199:7)
E/flutter (15982): #14     PrimaryPointerGestureRecognizer.handleEvent (package:flutter/src/gestures/recognizer.dart:467:9)
E/flutter (15982): #15     PointerRouter._dispatch (package:flutter/src/gestures/pointer_router.dart:76:12)
E/flutter (15982): #16     PointerRouter._dispatchEventToRoutes.<anonymous closure> (package:flutter/src/gestures/pointer_router.dart:117:9)
E/flutter (15982): #17     _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:379:8)
E/flutter (15982): #18     PointerRouter._dispatchEventToRoutes (package:flutter/src/gestures/pointer_router.dart:115:18)
E/flutter (15982): #19     PointerRouter.route (package:flutter/src/gestures/pointer_router.dart:101:7)
E/flutter (15982): #20     GestureBinding.handleEvent (package:flutter/src/gestures/binding.dart:218:19)
E/flutter (15982): #21     GestureBinding.dispatchEvent (package:flutter/src/gestures/binding.dart:198:22)
E/flutter (15982): #22     GestureBinding._handlePointerEvent (package:flutter/src/gestures/binding.dart:156:7)
E/flutter (15982): #23     GestureBinding._flushPointerEventQueue (package:flutter/src/gestures/binding.dart:102:7)
E/flutter (15982): #24     GestureBinding._handlePointerDataPacket (package:flutter/src/gestures/binding.dart:86:7)
E/flutter (15982): #25     _rootRunUnary (dart:async/zone.dart:1138:13)
E/flutter (15982): #26     _CustomZone.runUnary (dart:async/zone.dart:1031:19)
E/flutter (15982): #27     _CustomZone.runUnaryGuarded (dart:async/zone.dart:933:7)
E/flutter (15982): #28     _invoke1 (dart:ui/hooks.dart:273:10)
E/flutter (15982): #29     _dispatchPointerDataPacket (dart:ui/hooks.dart:182:5)
E/flutter (15982): 

Can you tell me the difference when processing xlsx and xls files?. I will probably learn and add features to handle xls in a pull request.