progress_overlay
Just another loading overlay (or progress HUD) widget that can be shown and hidden on demand, usually during time-consuming operations. I had to create this package because the available similar packages I used before did not work in some of my use cases.
Since I use Flutter BloC in my applications anyway, for better or for worse, this package also uses the flutter_bloc package.
Example
See the example for a complete sample app using the progress_overlay