ProgressIndicatorBuilder typedef
        ProgressIndicatorBuilder =
     Widget Function(BuildContext context, String url, DownloadProgress progress)
    
    
Builder function to create a progress indicator widget. The function is called every time a chuck of the image is downloaded from the web, but at least once during image loading.
Implementation
typedef ProgressIndicatorBuilder = Widget Function(
  BuildContext context,
  String url,
  DownloadProgress progress,
);