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 PictureProviders 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<AssetBundlePictureKey> obtainKey(PictureConfiguration picture) {
return SynchronousFuture<AssetBundlePictureKey>(
AssetBundlePictureKey(
bundle: bundle ?? picture.bundle ?? rootBundle,
name: keyName,
colorFilter: colorFilter,
),
);
}