Flutter 应用程序在使用 flutter_driver 运行时无法加载 Json 文件

Question

I'm trying to setup my Flutter app to automate screenshots using flutter_driver and integration tests, but the app is stuck at the point where it should await a future for a *.json file.
Does anybody know how to fix that?

Steps to Reproduce

1. Setup an app that needs to read a Json File (I used this method: String myJson = await rootBundle.loadString('my_resources/myjson.json');
2. Set up a flutter_driver test:

App.dart:

import 'package:flutter_driver/driver_extension.dart';
import 'package:flutter_project/main.dart' as app;

void main() {
  // This line enables the extension.
  enableFlutterDriverExtension();

  // Call the `main()` function of the app, or call `runApp` with
  // any widget you are interested in testing.
  app.main();
}

App_test.dart:

import 'package:flutter_driver/flutter_driver.dart';
import 'package:test/test.dart';

void main() {
  group('MyApp', () {
    FlutterDriver driver;

    setUpAll(() async {
      driver = await FlutterDriver.connect();
    });

    // Close the connection to the driver after the tests have completed.
    tearDownAll(() async {
      if (driver != null) {
        driver.close();
      }
    });
  });
}

3. Run the test with flutter drive --target=test_driver/app.dart

In my case the app is stuck at the await future for the *.json file from 1. Using the regular flutter run command everything works as expected.

flutter doctor -v

[✓] Flutter (Channel stable, v1.9.1+hotfix.2, on Mac OS X 10.14.6 18G95, locale de-DE)
    • Flutter version 1.9.1+hotfix.2 at /Users/patrick/Development/flutter
    • Framework revision 2d2a1ffec9 (2 weeks ago), 2019-09-06 18:39:49 -0700
    • Engine revision b863200c37
    • Dart version 2.5.0


[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
    • Android SDK at /Users/patrick/Library/Android/sdk
    • Android NDK location not configured (optional; useful for native profiling support)
    • Platform android-29, build-tools 29.0.2
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 10.3)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 10.3, Build version 10G8
    • CocoaPods version 1.7.5

[✓] Android Studio (version 3.5)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin version 39.0.3
    • Dart plugin version 191.8423
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)

[✓] VS Code (version 1.38.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.4.1

[✓] Connected device (2 available)
    • iPhone 7  • 5E5C912E-EA1D-438B-B5C5-E963D4BF9B33 • ios • com.apple.CoreSimulator.SimRuntime.iOS-12-4 (simulator)
    • iPhone Xʀ • EE0825D6-B8B4-4010-B954-CC913953F5D4 • ios • com.apple.CoreSimulator.SimRuntime.iOS-12-4 (simulator)

• No issues found!

Has anybody a solution for that? The *.json I want to import is a config file, so it's critical for me to import it for a smooth running. Would be really glad about any workaround.

Answer 1

There is an outstanding issue for this on Flutter GitHub. It appears there is an issue with the VM and an isolate in Flutter Driver.

See this comment https://github.com/flutter/flutter/issues/30641#issuecomment-524868136 it has a link to a fork of Flutter with an example of a test (here https://github.com/vishna/flutter/commit/2f858fc334fc2f43b92c318d02bdbf1ad0984033 ) that has solved this sort of issue for me in the passed

Also, maybe worth sharing your source code so that people can run/debug etc.

Answer 2

Use this code for loading JSON:

static Future<String> getJson(String file) async
    {
        final ByteData data = await rootBundle.load(file);
        if (data == null) return null;
        return utf8.decode(data.buffer.asUint8List());
    }

As @George Herbert said - there is opened Flutter issue at the moment. All code running compute will hang.