Is it possible to list the name of the Assets in a Flutter app?

Question

I need to know which ones Assets I uploaded it to an flutter, to reflect and make a decision.

I know I can list which ones Assets that I wish to climb into the app through the pubspec.yaml:

...

flutter:
  assets:
     - assets/image.png
     - scripts/

...

Documentation

In the above case, I’m saying I want to deliver the file on the way assets/image.png and also all files within the directory scripts/.

I can carry one Asset through the AssetBundle (like the rootBundle, already created a priori in Flutter).

For example, I can load the Asset scripts/V1.0__baseline.sql thus:

...

// import 'dart:async' show Future;
// import 'package:flutter/services.dart' show rootBundle;

Future<String> loadAsset() async {
  return await rootBundle.loadString('scripts/V1.0__baseline.sql');
}

Documentation

However, I couldn’t find anything in the documentation that would allow me to list the files inside the folder scripts to then be able to do something with them.

---

If that’s not possible, I’ll accept workarounds, how to generate a file with the folder listing scripts and add it as a Asset (solution similar to what I did to solve a analogous problem in Totalcross) through some configuration in the pubspec.yaml with any possible script call (bash/PowerShell/cmd/dart).

Answer 1

It is not necessary to generate a new file with the names of the others assets then carry it via AssetBundle, That’s because Flutter himself already does it :)

When building your application, realize that a file is generated AssetManifest.json with registration of all app Assets:

So taking into consideration an app with 3 name images image_1, image_2 and image_3 inside assets/images:

assets:
  - assets/images/

The content of the json file is as follows:

{  
   "packages/cupertino_icons/assets/CupertinoIcons.ttf":[  
      "packages/cupertino_icons/assets/CupertinoIcons.ttf"
   ],
   "assets/images/image_1.png":[  
      "assets/images/image_1.png"
   ],
   "assets/images/image_2.png":[  
      "assets/images/image_2.png"
   ],
   "assets/images/image_3.png":[  
      "assets/images/image_3.png"
   ]
}

With this then just read this file as you already know, and extract the necessary information, an example below:

Future<List<String>> _findFiles(BuildContext context) async {
  var manifest =
      await DefaultAssetBundle.of(context).loadString('AssetManifest.json');

  Map map = json.decode(manifest);
  List<String> values =
      map.keys.where((k) => k.contains('assets/image')).toList();
  return Future.value(values);
}

Above, read the file with DefaultAssetBundle, made the json code with dart:convert for a Map, and extracted the necessary Keys.

Full example:

import 'dart:convert';
import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: SafeArea(
        child: Scaffold(
          appBar: AppBar(
            title: Text('Nome dos Assets'),
          ),
          body: FutureBuilder(
            future: _findFiles(context),
            builder:
                (BuildContext context, AsyncSnapshot<List<String>> snapshot) {
              if (snapshot.hasData) {
                final names = snapshot.data;

                return ListView.builder(
                  itemCount: names.length,
                  itemBuilder: (BuildContext context, int index) {
                    final asset = names[index];

                    return ListTile(title: Text(asset));
                  },
                );
              }

              return Center(
                child: Text('Carregando'),
              );
            },
          ),
        ),
      ),
    );
  }
}

The result: