How to access files within an asset folder and track the length

Question

I want to be able to track the number of files in the main directory and if possible the sub directory as well.

The below code builds more than I expect. I had the solution and actually don't know where the 'assestManifest.json' directory is but is kind of works but return is more than what I have in my directory. Printing the last index shows there is more files aside mine.

Please help me!

`

FutureBuilder<String>(
          future:
              DefaultAssetBundle.of(context).loadString('AssetManifest.json'),
          builder: (context, snapshot) {
            if (snapshot.hasData) {
              Map? jsonMap = json.decode(snapshot.data!);
              List? file = jsonMap?.keys.toList();
              print(file?[49]);
              return GridView.builder(
                physics: const NeverScrollableScrollPhysics(),
                padding: const EdgeInsets.symmetric(horizontal: 15),
                gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
                  crossAxisCount: 5,
                  mainAxisSpacing: 1,
                  mainAxisExtent: 60,
                  crossAxisSpacing: 15,
                ),
                itemCount: file?.length,
                itemBuilder: (context, index) {
                  return Text(
                    '${index + 1}',
                    style: Theme.of(context).textTheme.headline2,
                  );
                },
              );
            }
            return Center(
              child: Text('Loading...'),
            );
          }),
   `