1. override
ImageStreamCompleter load(FileImage key)

Converts a key into an ImageStreamCompleter, and begins fetching the image.

Source 

@override
ImageStreamCompleter load(FileImage key) {
  return new OneFrameImageStreamCompleter(
    _loadAsync(key),
    informationCollector: (StringBuffer information) {
      information.writeln('Path: ${file?.path}');
    }
  );
}