Model
- The type of the model.Data
- The type of the data that can be used by a
ResourceDecoder
to decode a resource.public interface ModelLoader<Model,Data>
DataFetcher
to obtain the data for a resource represented by the
model.
This interface has two objectives: 1. To translate a specific model into a data type that can be decoded into a resource. 2. To allow a model to be combined with the dimensions of the view to fetch a resource of a specific size. This not only avoids having to duplicate dimensions in xml and in your code in order to determine the size of a view on devices with different densities, but also allows you to use layout weights or otherwise programmatically put the dimensions of the view without forcing you to fetch a generic resource size. The smaller the resource you fetch, the less bandwidth and battery life you use, and the lower your memory footprint per resource.
Modifier and Type | Interface and Description |
---|---|
static class |
ModelLoader.LoadData<Data>
Contains a set of
Keys identifying the source of the load,
alternate cache keys pointing to equivalent data, and a
DataFetcher that can be used to fetch data not found in
cache. |
Modifier and Type | Method and Description |
---|---|
ModelLoader.LoadData<Data> |
buildLoadData(Model model,
int width,
int height,
Options options)
Returns a
ModelLoader.LoadData containing a
DataFetcher required to decode the resource
represented by this model, as well as a set of Keys that
identify the data loaded by the DataFetcher as well as an
optional list of alternate keys from which equivalent data can be loaded. |
boolean |
handles(Model model)
Returns true if the given model is a of a recognized type that this loader can probably load.
|
@Nullable ModelLoader.LoadData<Data> buildLoadData(@NonNull Model model, int width, int height, @NonNull Options options)
ModelLoader.LoadData
containing a
DataFetcher
required to decode the resource
represented by this model, as well as a set of Keys
that
identify the data loaded by the DataFetcher
as well as an
optional list of alternate keys from which equivalent data can be loaded. The
DataFetcher
will not be used if the resource is already cached.
Note - If no valid data fetcher can be returned (for example if a model has a null URL), then it is acceptable to return a null data fetcher from this method.
model
- The model representing the resource.width
- The width in pixels of the view or target the resource will be loaded into, or
Target.SIZE_ORIGINAL
to indicate that
the resource should be loaded at its original width.height
- The height in pixels of the view or target the resource will be loaded into, or
Target.SIZE_ORIGINAL
to indicate that
the resource should be loaded at its original height.boolean handles(@NonNull Model model)
For example, you may want multiple Uri -> InputStream loaders. One might handle media store Uris, another might handle asset Uris, and a third might handle file Uris etc.
This method is generally expected to do no I/O and complete quickly, so best effort
results are acceptable. ModelLoaders
that return true from this method may
return null
from buildLoadData(Object, int, int, Options)