Hosting an executable within a Flutter application

Question

I have a basic flutter project running on android where when the application starts, I write an executable bundled in my assets.

  static String appInternalPath = '/data/data/com.maksimdan.face_merger';

  void writeExecutable() async {
    var executablePath = join(appInternalPath, 'main');

    if (await File(executablePath).exists()) {
      File(executablePath).delete();
      print('deleted old executable');
    } else {
      print('not executable exists');
    }

    ByteData data = await rootBundle.load('lib/py/dist/main');
    List<int> bytes =
        data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
    await File(executablePath).writeAsBytes(bytes);
    print('wrote new executable');
  }

Sometime later in my code I try to run it.

  void invokeExecutable() async {
    String executablePath = join(appInternalPath, 'main');
    Process.run('chmod', ['u+x', executablePath]).then((ProcessResult results) {
      Process.run(executablePath, []).then((ProcessResult results) {
        print(results.stdout);
      });
    });
  }

But obtain a permission denied error.

E/flutter (31825): [ERROR:flutter/lib/ui/ui_dart_state.cc(186)] Unhandled Exception: ProcessException: Permission denied
E/flutter (31825):   Command: /data/data/com.maksimdan.flutter_general/main 
E/flutter (31825): #0      _ProcessImpl._start (dart:io-patch/process_patch.dart:390:33)
E/flutter (31825): #1      Process.start (dart:io-patch/process_patch.dart:36:20)
E/flutter (31825): #2      _runNonInteractiveProcess (dart:io-patch/process_patch.dart:565:18)
E/flutter (31825): #3      Process.run (dart:io-patch/process_patch.dart:47:12)
E/flutter (31825): #4      _MyHomePageState.invokeExecutable.<anonymous closure> (package:flutter_general/main.dart:51:15)
E/flutter (31825): #5      _rootRunUnary (dart:async/zone.dart:1362:47)
E/flutter (31825): #6      _CustomZone.runUnary (dart:async/zone.dart:1265:19)
E/flutter (31825): <asynchronous suspension>

I've also tried:

      Process.run('/system/bin/chmod', ['744', path]).then((ProcessResult results) {
        print('shell1 complete');
        Process.run(path, []).then((ProcessResult results) {
          print('shell2 complete');
          print(results.stdout);
        });
      });

My executable:

// 'Hello World!' program 
 
#include <iostream>
 
int main()
{
  std::cout << "Hello World!" << std::endl;
  return 0;
}

>> g++ main.cc -o main

Is there a way to run your own executables in flutter with the proper permissions? On native android, there is an option to file.setExecutable(true); using this strategy. (Hosting an executable within Android application)

Or will I have to experiment with method channels?

---

pubspec.yml

name: face_merger
description: A new Flutter project.

version: 1.0.0+1

environment:
  sdk: ">=2.1.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter

  sqflite: ^1.3.0+2
  process_run: ^0.10.10+1
  cupertino_icons: ^0.1.3

dev_dependencies:
  flutter_test:
    sdk: flutter


flutter:
  uses-material-design: true
  assets:
    - lib/py/dist/main

I also verified that the file was written to the internal memory of on the device that I expected it to be written to using android studio's device explore.

Answer 1

Besides the writable permission you need to have readable permission in your app.

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.xxx.yyy">
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

...