works in debug but throws Unhandled in release build

[sidetraxaudio]

Nice work - much appreciated however..
Compiling in release mode throws this:
Unhandled Exception: LateInitializationError: Local 'result' has not been initialized.

it seems to be related to the following line in builders/widget.dart
WidgetsBinding.instance!.addPostFrameCallback(_captureImage);

Symptom: perfect in debug, blank screen in release
Fixing it is beyond my skill as I'm just learning.

E/flutter (18180): #2 _PageTurnWidgetState._captureImage (package:ssv1/book_screen/builders/widget.dart:40)
E/flutter (18180): #3 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1144)
E/flutter (18180): #4 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1090)
E/flutter (18180): #5 SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:998)
E/flutter (18180): #6 _rootRun (dart:async/zone.dart:1354)
E/flutter (18180): #7 _CustomZone.run (dart:async/zone.dart:1258)
E/flutter (18180): #8 _CustomZone.runGuarded (dart:async/zone.dart:1162)
E/flutter (18180): #9 _invoke (dart:ui/hooks.dart:167)
E/flutter (18180): #10 PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:259)
E/flutter (18180): #11 _drawFrame (dart:ui/hooks.dart:126)
E/flutter (18180):
E/flutter (18180): [ERROR:flutter/lib/ui/ui_dart_state.cc(186)] Unhandled Exception: LateInitializationError: Local 'result' has not been initialized.
E/flutter (18180): #0 LateError._throwLocalNotInitialized (dart:_internal-patch/internal_patch.dart:208)
E/flutter (18180): #1 RenderObject.debugNeedsPaint (package:flutter/src/rendering/object.dart:2112)
E/flutter (18180): #2 _PageTurnWidgetState._captureImage (package:ssv1/book_screen/builders/widget.dart:40)
E/flutter (18180): #3 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1144)
E/flutter (18180): #4 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1090)
E/flutter (18180): #5 SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:998)
E/flutter (18180): #6 _rootRun (dart:async/zone.dart:1354)
E/flutter (18180): #7 _CustomZone.run (dart:async/zone.dart:1258)
E/flutter (18180): #8 _CustomZone.runGuarded (dart:async/zone.dart:1162)
E/flutter (18180): #9 _invoke (dart:ui/hooks.dart:167)
E/flutter (18180): #10 PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:259)
E/flutter (18180): #11 _drawFrame (dart:ui/hooks.dart:126)
E/flutter (18180):
E/flutter (18180): [ERROR:flutter/lib/ui/ui_dart_state.cc(186)] Unhandled Exception: LateInitializationError: Local 'result' has not been initialized.
E/flutter (18180): #0 LateError._throwLocalNotInitialized (dart:_internal-patch/internal_patch.dart:208)
E/flutter (18180): #1 RenderObject.debugNeedsPaint (package:flutter/src/rendering/object.dart:2112)
E/flutter (18180): #2 _PageTurnWidgetState._captureImage (package:ssv1/book_screen/builders/widget.dart:40)
E/flutter (18180): #3 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1144)
E/flutter (18180): #4 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1090)
E/flutter (18180): #5 SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:998)
E/flutter (18180): #6 _rootRun (dart:async/zone.dart:1354)
E/flutter (18180): #7 _CustomZone.run (dart:async/zone.dart:1258)
E/flutter (18180): #8 _CustomZone.runGuarded (dart:async/zone.dart:1162)
E/flutter (18180): #9 _invoke (dart:ui/hooks.dart:167)
E/flutter (18180): #10 PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:259)
E/flutter (18180): #11 _drawFrame (dart:ui/hooks.dart:126)
E/flutter (18180):
E/flutter (18180): [ERROR:flutter/lib/ui/ui_dart_state.cc(186)] Unhandled Exception: LateInitializationError: Local 'result' has not been initialized.
E/flutter (18180): #0 LateError._throwLocalNotInitialized (dart:_internal-patch/internal_patch.dart:208)
E/flutter (18180): #1 RenderObject.debugNeedsPaint (package:flutter/src/rendering/object.dart:2112)
E/flutter (18180): #2 _PageTurnWidgetState._captureImage (package:ssv1/book_screen/builders/widget.dart:40)
E/flutter (18180): #3 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1144)
E/flutter (18180): #4 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1090)
E/flutter (18180): #5 SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:998)
E/flutter (18180): #6 _rootRun (dart:async/zone.dart:1354)
E/flutter (18180): #7 _CustomZone.run (dart:async/zone.dart:1258)
E/flutter (18180): #8 _CustomZone.runGuarded (dart:async/zone.dart:1162)
E/flutter (18180): #9 _invoke (dart:ui/hooks.dart:167)
E/flutter (18180): #10 PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:259)
E/flutter (18180): #11 _drawFrame (dart:ui/hooks.dart:126)
E/flutter (18180):
E/flutter (18180): [ERROR:flutter/lib/ui/ui_dart_state.cc(186)] Unhandled Exception: LateInitializationError: Local 'result' has not been initialized.
E/flutter (18180): #0 LateError._throwLocalNotInitialized (dart:_internal-patch/internal_patch.dart:208)
E/flutter (18180): #1 RenderObject.debugNeedsPaint (package:flutter/src/rendering/object.dart:2112)
E/flutter (18180): #2 _PageTurnWidgetState._captureImage (package:ssv1/book_screen/builders/widget.dart:40)
E/flutter (18180): #3 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1144)
E/flutter (18180): #4 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1090)
E/flutter (18180): #5 SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:998)
E/flutter (18180): #6 _rootRun (dart:async/zone.dart:1354)
E/flutter (18180): #7 _CustomZone.run (dart:async/zone.dart:1258)
E/flutter (18180): #8 _CustomZone.runGuarded (dart:async/zone.dart:1162)
E/flutter (18180): #9 _invoke (dart:ui/hooks.dart:167)
E/flutter (18180): #10 PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:259)
E/flutter (18180): #11 _drawFrame (dart:ui/hooks.dart:126)
E/flutter (18180):
E/flutter (18180): [ERROR:flutter/lib/ui/ui_dart_state.cc(186)] Unhandled Exception: LateInitializationError: Local 'result' has not been initialized.
E/flutter (18180): #0 LateError._throwLocalNotInitialized (dart:_internal-patch/internal_patch.dart:208)
E/flutter (18180): #1 RenderObject.debugNeedsPaint (package:flutter/src/rendering/object.dart:2112)
E/flutter (18180): #2 _PageTurnWidgetState._captureImage (package:ssv1/book_screen/builders/widget.dart:40)
E/flutter (18180): #3 SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1144)
E/flutter (18180): #4 SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1090)
E/flutter (18180): #5 SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:998)
E/flutter (18180): #6 _rootRun (dart:async/zone.dart:1354)
E/flutter (18180): #7 _CustomZone.run (dart:async/zone.dart:1258)
E/flutter (18180): #8 _CustomZone.runGuarded (dart:async/zone.dart:1162)
E/flutter (18180): #9 _invoke (dart:ui/hooks.dart:167)
E/flutter (18180): #10 PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:259)
E/flutter (18180): #11 _drawFrame (dart:ui/hooks.dart:126)

[sidetraxaudio]

(The following has failed to resolve)
Downgrade to stable, cleanup, cache etc etc, copy to new project, compile with --no-shrink... all failed,

• Debug works perfectly with zero output problems reported on real phone, emulator, windows and chrome builds.
• Release compile fails on all platforms in exactly the same way.

[tuannvm2109]

After a while of edit and test, I have found a quick fix about this problem, you could change the function _captureImage to like this and it will work on release build, (You 'll need to copy this library to your own directory to edit PageTurnWidget file)

void _captureImage(Duration timeStamp) async {
await Future.delayed(const Duration(milliseconds: 20));
final pixelRatio = MediaQuery.of(context).devicePixelRatio;
final boundary =
_boundaryKey.currentContext?.findRenderObject() as RenderRepaintBoundary;
// if (boundary.debugNeedsPaint) {
// await Future.delayed(const Duration(milliseconds: 20));
// return _captureImage(timeStamp);
// }
final image = await boundary.toImage(pixelRatio: pixelRatio);
setState(() => _image = image);
}

[sidetraxaudio]

Thanks mate - it works. I was hoping for better performance once I could get it to work in release mode but unfortunately its still unusably slow . I might look into how to make the performance better. If you find anything please make sure you post it.

[jmgeffroy]

Hi there! I'm writing 1 year later, but who knows, this can be interesting to someone: the original code snippet was probably this Gist. And it's very, very smooth.
I haven't found any relevant difference that might cause this huge difference, but I'll share if I find it.