Fix VoidCallback error

[mapacheverdugo]

I was having an error with the VoidCallback type.

The solution was to simply import the dart:ui library

Error: Type 'VoidCallback' not found.
../…/utils/downloader_utils.dart:23
final VoidCallback onDone;
^^^^^^^^^^^^
: Error: 'VoidCallback' isn't a type.
../…/utils/downloader_utils.dart:23
final VoidCallback onDone;
^^^^^^^^^^^^

[Livekus]

update pub.dev please

[Hzz-Hzz]

This solution resolved my problem too.
In case someone misunderstands the solution above, I import the dart:ui right inside the library's source code.