flutter: ══╡ EXCEPTION CAUGHT BY SCHEDULER LIBRARY ╞═════════════════════════════════════════════════════════
flutter: The following UnsupportedError was thrown during a scheduler callback:
flutter: Unsupported operation: Infinity or NaN toInt
flutter:
flutter: When the exception was thrown, this was the stack:
flutter: #0 double.toInt (dart:core-patch/double.dart:192:36)
flutter: #1 double.round (dart:core-patch/double.dart:160:34)
flutter: #2 _PositionedListState._schedulePositionNotificationUpdate.<anonymous closure> (package:scrollable_positioned_list/src/positioned_list.dart:324:45)
flutter: #3 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1119:15)
flutter: #4 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1065:9)
flutter: #5 SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:973:5)
flutter: #9 _invoke (dart:ui/hooks.dart:157:10)
flutter: #10 PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:253:5)
flutter: #11 _drawFrame (dart:ui/hooks.dart:120:31)
flutter: (elided 3 frames from dart:async)
flutter: ════════════════════════════════════════════════════════════════════════════════════════════════════
このように「Unsupported operation: Infinity or NaN toInt」が発生し現在位置が取得できない。
このバグは 2020/11/15 現在最新の scrollable_positioned_list 0.1.8 でも修正されていない。
対応方法としては、
https://github.com/google/flutter.widgets/issues/173#issuecomment-704673432
にかかれているように修正パッチを当ててくれているバージョンの scrollable_positioned_list を用いること。
本家への PR も出してくれているようで、https://github.com/google/flutter.widgets/pull/180 がマージされ次第修正されると思われる。