Flutter：加载资产错误，除非热重新加载（BLOC + MultiImagePicker）

Question

I've got a strange problem where loading a file converted from MultiImagePicker only loads successfully after hot reloading the page, otherwise it returns the following error:

Unhandled Exception: Unable to load asset: /storage/emulated/0/DCIM/Camera/IMG_20191105_104542.jpg

Steps:

1. initState loads existing image Strings from Firestore, which are cached to File via DefaultCacheManager and added to tmpGalleryImages list.

2. Adding images uses MultiImagePicker, which are then converted from Asset to File and added to tmpGalleryImages list.

3. I created a SetState button to test reloading the state, but still getting the above error after calling SetState - so I'm extremely confused why it only works after hot reload?

Note: Going through the hassle of converting to File allows me to combine both local images (Asset) and Firestore images (String) into one List that can be edited and re-uploaded to Firestore

initState:

 @override
void initState() {
super.initState();
setState(() {
  _galleryBloc.getGalleryImages(
      docRef: Firestore.instance.collection("galleries").document("gal_${widget.docId}"),
      tmpGalleryImages: widget.tmpGalleryImages,
      callback: widget.callback);
});

}

StreamBuilder:

@override
Widget build(BuildContext context) {
return StreamBuilder<List<File>>(
  stream: _galleryBloc.multipleImageStream,
  builder: (context, snapshot) {
    if (snapshot.connectionState == ConnectionState.none) {
      print("none");
    }
    if (snapshot.connectionState == ConnectionState.waiting) {
      print("Waiting");
    }

    return Column(
      children: <Widget>[
        GridView.builder(
          gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 4),
          itemCount: snapshot.data.length < widget.imageLimit ? snapshot.data.length + 1 : snapshot.data.length,
          itemBuilder: (context, index) {
            return index < snapshot.data.length
                ? GalleryStepperThumbnail(
                    file: snapshot.data[index],
                    onTap: () {
                      _showGalleryStepperOptions(
                        context: context,
                        tmpGalleryImages: snapshot.data,
                        imageLimit: widget.imageLimit,
                        file: snapshot.data[index],
                        fileName: "img_${index + 1}",
                      );
                    })
                : snapshot.data.length < widget.imageLimit
                    ? InkWell(
                        onTap: () => _showGalleryStepperOptions(
                          context: context,
                          tmpGalleryImages: snapshot.data,
                          imageLimit: widget.imageLimit,
                          fileName: "img_${index + 1}",
                        ),
                        child: Card(
                          child: Center(
                            child: Icon(Icons.add),
                          ),
                        ),
                      )
                    : Offstage();
              },
            ),

BLOC:

class GalleryBloc {
  final _multipleImageController = StreamController<List<File>>.broadcast();
  Stream<List<File>> get multipleImageStream => _multipleImageController.stream;

// -----------------------------------------------------------------------------
// Load existing gallery images
// -----------------------------------------------------------------------------
  Future<void> getGalleryImages({DocumentReference docRef, List<File> tmpGalleryImages, Function callback}) async {
    try {
      await docRef.get().then(
        (value) async {
          if (value.data != null && tmpGalleryImages.length == 0) {
            for (var img in value.data['gallery_images']) {
              File fetchedFile = await DefaultCacheManager().getSingleFile(img);
          tmpGalleryImages.add(fetchedFile);
            }
          }
        },
       );
    } catch (e) {
      print(e.toString());
    }
    callback(tmpGalleryImages);
    _multipleImageController.sink.add(tmpGalleryImages);
   }


// -----------------------------------------------------------------------------
// Convert File to Asset
// -----------------------------------------------------------------------------
  Future<File> _convertAssetToFile(String path) async {
    final byteData = await rootBundle.load(path);

    final file = File(path);
    await file.writeAsBytes(byteData.buffer.asUint8List(byteData.offsetInBytes, byteData.lengthInBytes));
    return file;
  }

// -----------------------------------------------------------------------------
// Select Multiple Images
// -----------------------------------------------------------------------------
  Future<void> pickMultipleImages({List<File> tmpGalleryImages, int imageLimit, Function callback}) async {

    try {
      await MultiImagePicker.pickImages(
        maxImages: imageLimit - tmpGalleryImages.length,
  ).then((chosenImages) async {
        for (var path in chosenImages) {
         await _convertAssetToFile(await path.filePath).then(
        (convertedFile) {
              tmpGalleryImages.add(convertedFile);
             },
          );
        }
      });
    } on Exception catch (e) {
      print(e.toString());
    }

    _multipleImageController.sink.add(tmpGalleryImages);
    callback(tmpGalleryImages);
  }

If anyone could offer some guidance on where I'm going wrong, I would really appreciate that!

UPDATED CODE BASED ON IGOR'S ANSWER (WORKING):

 // -----------------------------------------------------------------------------
// Convert File to Asset
// -----------------------------------------------------------------------------
  Future<File> _convertAssetToFile(String path) async {

    final file = File(path);

    return file;
  }

Answer 1

Do not use rootBundle to open files that were not packed with the app via pubspec.yaml. Open them with File class.

The rootBundle contains the resources that were packaged with the application when it was built. To add resources to the rootBundle for your application, add them to the assets subsection of the flutter section of your application's pubspec.yaml manifest.