LateInitializationError occurs when used in isolate

[tcdspring]

E/flutter (24445): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: LateInitializationError: Field '_instance@2084288322' has not been initialized.
E/flutter (24445): #0 SodiumPlatform._instance (package:sodium_libs/src/sodium_platform.dart)
E/flutter (24445): #1 SodiumPlatform.instance (package:sodium_libs/src/sodium_platform.dart:21:41)

sodium_libs version: 1.2.0
flutter version: 2.8

used like this:

await Executor().execute(
    arg1: str1,
    fun1: (String demo) async {
      // this is an isolate
      final sodium = await CustomSodiumInit.init();   // this line occurs LateInitializationError 
      final encData = sodium.crypto.secretBox.easy(...);
      // ...
    },
  );

CustomSodiumInit code:

// ......
static Future<sodium.Sodium> init({
    @Deprecated('initNative is no longer required and will be ignored.')
        bool initNative = true,
  }) =>
      _instanceLock.synchronized(() async {
        if (_instance != null) {
          return _instance!;
        }
        
        // Comment out this line or an exception(Unhandled Exception: UI actions are only available on root isolate) will occur
        // WidgetsFlutterBinding.ensureInitialized();
        _instance = await SodiumPlatform.instance.loadSodium();
        if (!kReleaseMode) {
          if (_instance!.version < _expectedVersion) {
            // ignore: avoid_print
            print(
              'WARNING: The embedded libsodium is outdated! '
              'Expected $_expectedVersion, but was ${_instance!.version}}. '
              '${SodiumPlatform.instance.updateHint}',
            );
          }
        }
        return _instance!;
      });

sodium_libs version 1.1.1 will work, but 1.2.0 not

[Skycoder42]

SodiumPlatform.instance is initialized automatically by flutter when the plugin is loaded. This happens as part of the WidgetsBinding.ensureInitialized() in normal code. This is not automatically executed when launching a new isolate, thus it does not get initialized. It did work with older versions, as back then flutter did not support loading dart plugins automatically.

This is not a bug, but expected behaviour. You have to do one of the following things to use the plugin in a different isolate:

1. Simply call WidgetsBinding.ensureInitialized() in your Isolate
2. Use a plugin like flutter_isolate that takes care of that for you.
3. Manually initialize the instance. This requires you to now which platform you are on and select the correct implementation. See https://github.com/Skycoder42/libsodium_dart_bindings/tree/main/packages/sodium_libs/lib/src/platforms where you can find the concrete implementations. For example, to initialize it for Android, you could call SodiumAndroid.registerWith().