loadLocalOrNetworkImageBytes function

Stream<Uint8List> loadLocalOrNetworkImageBytes({ required LoadImageOption option, StreamController<ImageChunkEvent>? chunkEvents, void evictImageAsync()?, })

Loads local image bytes or cached network image bytes, using given option and chunkEvents. If the image is downloaded, it will also be recorded to given CacheManager.

Implementation

Stream<Uint8List> loadLocalOrNetworkImageBytes({
  required LoadImageOption option,
  StreamController<ImageChunkEvent>? chunkEvents,
  void Function()? evictImageAsync,
}) async* {
  // 1. get file and url
  io.File? file;
  String? url;
  if (!option.useFuture) {
    file = option.file; // nullable
    url = option.url; // nullable
  } else {
    file = await option.fileFuture; // nullable
    url = await option.urlFuture; // nullable
  }

  // 2. check file and url validity
  var useFile = false;
  var useUrl = false;
  if (file == null) {
    if (url == null) {
      var ex = const LoadImageException.bothNull();
      option.onFileLoading?.call();
      option.onFileLoaded?.call(ex);
      throw ex; // => null file, null url
    } else {
      useUrl = true; // => null file, non-null url
    }
  } else {
    var existed = false;
    try {
      existed = await file.exists();
    } catch (_) {
      if (option.fileMustExist) {
        // throw exceptions only if fileMustExist flag is true
        rethrow;
      }
    }
    if (existed) {
      useFile = true; // => valid file
    } else if (option.fileMustExist) {
      var ex = LoadImageException.notExistedFile(filepath: file.path);
      option.onFileLoading?.call();
      option.onFileLoaded?.call(ex);
      throw ex; // => invalid file
    } else {
      if (url == null) {
        var ex = LoadImageException.notExistedFileNullUrl(filepath: file.path);
        option.onFileLoading?.call();
        option.onFileLoaded?.call(ex);
        throw ex; // => invalid file, null url
      } else {
        useUrl = true; // => invalid file, non-null url
      }
    }
  }

  // load local image
  if (useFile) {
    option.onFileLoading?.call();
    yield* _loadLocalImageBytes(
      file: file!,
      chunkEvents: chunkEvents,
      evictImageAsync: evictImageAsync,
      onLoaded: option.onFileLoaded,
    );
  }

  // load cached network image
  if (useUrl) {
    option.onUrlLoading?.call();
    yield* _loadCachedNetworkImageBytes(
      url: url!,
      chunkEvents: chunkEvents,
      evictImageAsync: evictImageAsync,
      headers: option.headers,
      cacheManager: option.cacheManager,
      cacheKey: option.cacheKey,
      maxWidth: option.maxWidth,
      maxHeight: option.maxHeight,
      asyncHeadFirst: option.asyncHeadFirst,
      networkTimeout: option.networkTimeout,
      onLoaded: option.onUrlLoaded,
    );
  }
}