How to write to and read from a file in my assets folder in a flutter app?

Question

I am trying to write to and read from a file that is in the assets folder in a flutter app. Generally, how should it be done? I tried the following approach:-

void writeToFile(String data) async {
  final String filename = 'colors.json';
  await rootBundle.load('assets/docs/colors.json').then((f){
    print("file loaded successfully.");
    File file = File(filename);
    file.writeAsString(data);
  });
}

However, this results in the following error: E/flutter ( 4944): FileSystemException: Cannot open file, path = 'colors.json' (OS Error: Read-only file system, errno = 30)

OS: Mac Catalina

pubspec entry:

assets:
- assets/docs/colors.json

write permission to what? I do not intend to write to the android or ios device. I would like to write something to the file that's in the assets folder of my app, that too in the background. User may not have access to writing as well... — iMujtaba8488, Mar 28 '20 at 08:54
though tried that, still it didn't work. Still the same error message. — iMujtaba8488, Mar 28 '20 at 09:04
What if i would like to record logs of my app in one of my source files, only for testing purposes? — iMujtaba8488, Mar 30 '20 at 16:13
@iMutjtaba8488 Did you manage to write to the file on assets folder after all? — ToroLoco, Jun 29 '21 at 07:40

score 0 · Answer 1 · answered Jul 21 '22 at 14:13

You can't write the files in the assets. But you can use path_provider to save the modified file in app directory.

Per documentation "Adding assets and images"

An asset is a file that is bundled and deployed with your app, and is accessible at runtime.

...

During a build, Flutter places assets into a special archive called the asset bundle that apps read from at runtime.

How to write to and read from a file in my assets folder in a flutter app?

1 Answers1