obtainKey method
Converts a pictureProvider's settings plus a pictureConfiguration to a key that describes the precise picture to load.
The type of the key is determined by the subclass. It is a value that
unambiguously identifies the picture (including its scale) that the load
method will fetch. Different PictureProvider
s given the same constructor
arguments and PictureConfiguration
objects should return keys that are
'==' to each other (possibly by using a class for the key that itself
implements ==).
Implementation
@override
Future<AdvancedNetworkSvg> obtainKey(PictureConfiguration picture) {
return SynchronousFuture<AdvancedNetworkSvg>(this);
}