google_ml_kit - how to force download of text recognition module at compile?

Question

I am new to Flutter, trying to write a simple module to pick an image and pass it to google_ml_kit for on device OCR text recognition only. I have set the Android min SDK version to 21 and updated the build.gradle to use FileNotFoundException. Image pick works fine, but when I pass the picked image file to the ml_kit function, I get a set of errors that seem to indicate the OCR module is missing and needs to be downloaded. Is there a way to force this to happen at compile time?

import 'dart:async';
import 'dart:io';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:image_picker/image_picker.dart';
import 'package:google_ml_kit/google_ml_kit.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: 'Image Selector with OCR',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key ?key}) : super(key: key);

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  File? txtImage;
  String? imageString;

  Future getImage()async{
    try {
      final image = await ImagePicker().pickImage(source: ImageSource.gallery);
      if (image == null) return;
      final imageFile = File(image.path);
      final ocrText = await readText(imageFile);
      setState(()=>this.imageString = ocrText);
      setState(()=>this.txtImage = imageFile);
    } on PlatformException catch(e){print('error'+e.message.toString());}
  }

  Future readText(_file)async{

    try {
      final inputImage = InputImage.fromFile(_file);
      final textDetector = GoogleMlKit.vision.textDetector();
      final RecognisedText recognisedText = await textDetector.processImage(
          inputImage);
      print(recognisedText);
      return (recognisedText);
    } on PlatformException catch(e){print(e.message.toString());}
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Reading Assistant'),
      ),
      body: Center(child: Column(mainAxisAlignment: MainAxisAlignment.center,
        children: [
          txtImage != null ? Row(mainAxisAlignment: MainAxisAlignment.spaceEvenly,children: [
            Image.file(txtImage!),Text('OCR:')]) : Text('select an image'),
        ],
      )),

      floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
      floatingActionButton: Stack(
        fit: StackFit.expand,
        children: [
          Positioned(
            right: 20,
            bottom: 10,
            child: FloatingActionButton(
              heroTag: 'pick',
              onPressed: () {getImage();},
              child: Icon(
                Icons.photo_album_outlined,
                size: 40,
              ),
            ),
          ),
          Positioned(
            bottom: 10,
            right: 90,
            child: FloatingActionButton(
              heroTag: 'camera',
              onPressed: () {/* TODO implement camera later */},
              child: Icon(
                Icons.camera,
                size: 40,
              ),
            ),
          ),
        ],
      ),


    );;
  }
}

W/DynamiteModule( 8758): Local module descriptor class for com.google.android.gms.vision.ocr not found. I/DynamiteModule( 8758): Considering local module com.google.android.gms.vision.ocr:0 and remote module com.google.android.gms.vision.ocr:0 E/Vision ( 8758): Error loading module com.google.android.gms.vision.ocr optional module true: gv: No acceptable module found. Local version is 0 and remote version is 0. I/Vision ( 8758): Request download for engine ocr D/skia ( 8758): Shader compilation error D/skia ( 8758): ------------------------ D/skia ( 8758): Errors: D/skia ( 8758): D/skia ( 8758): Shader compilation error D/skia ( 8758): ------------------------ D/skia ( 8758): Errors: D/skia ( 8758): D/skia ( 8758): Shader compilation error D/skia ( 8758): ------------------------ D/skia ( 8758): Errors: D/skia ( 8758): D/skia ( 8758): Shader compilation error D/skia ( 8758): ------------------------ D/skia ( 8758): Errors: D/skia ( 8758): D/TransportRuntime.SQLiteEventStore( 8758): Storing event with priority=VERY_LOW, name=FIREBASE_ML_SDK for destination cct D/TransportRuntime.JobInfoScheduler( 8758): Upload for context TransportContext(cct, VERY_LOW, MSRodHRwczovL2ZpcmViYXNlbG9nZ2luZy5nb29nbGVhcGlzLmNvbS92MGNjL2xvZy9iYXRjaD9mb3JtYXQ9anNvbl9wcm90bzNc) is already scheduled. Returning... D/TransportRuntime.SQLiteEventStore( 8758): Storing event with priority=VERY_LOW, name=FIREBASE_ML_SDK for destination cct D/TransportRuntime.JobInfoScheduler( 8758): Upload for context TransportContext(cct, VERY_LOW, MSRodHRwczovL2ZpcmViYXNlbG9nZ2luZy5nb29nbGVhcGlzLmNvbS92MGNjL2xvZy9iYXRjaD9mb3JtYXQ9anNvbl9wcm90bzNc) is already scheduled. Returning... I/flutter ( 8758): com.google.mlkit.common.MlKitException: Waiting for the text recognition module to be downloaded. Please wait.

Answer 1

I solved this by changing the emulator in Android Studio to use a different emulator with the latest version of Play Store enabled (not all the images in the AVD manager have these)

Answer 2

As you can see in this link https://developers.google.com/ml-kit/migration/android#new , only beta version of Text Recognition is working without need to download something. So I would encourage you to make the google_ml_kit package local to your flutter project and replace the text recognition implementation with

implementation 'com.google.mlkit:text-recognition:16.0.0-beta1'

then that error won't appear in toast message.