com.bumptech.glide.load.model.ModelLoader Maven / Gradle / Ivy
package com.bumptech.glide.load.model;
import android.support.annotation.Nullable;
import com.bumptech.glide.load.Key;
import com.bumptech.glide.load.Options;
import com.bumptech.glide.load.data.DataFetcher;
import com.bumptech.glide.util.Preconditions;
import java.util.Collections;
import java.util.List;
/**
* A factory interface for translating an arbitrarily complex data model into a concrete data type
* that can be used by an {@link 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.
*
* @param The type of the model.
* @param The type of the data that can be used by a
* {@link com.bumptech.glide.load.ResourceDecoder} to decode a resource.
*/
public interface ModelLoader {
/**
* Contains a set of {@link com.bumptech.glide.load.Key Keys} identifying the source of the load,
* alternate cache keys pointing to equivalent data, and a
* {@link com.bumptech.glide.load.data.DataFetcher} that can be used to fetch data not found in
* cache.
*
* @param The type of data that well be loaded.
*/
class LoadData {
public final Key sourceKey;
public final List alternateKeys;
public final DataFetcher fetcher;
public LoadData(Key sourceKey, DataFetcher fetcher) {
this(sourceKey, Collections.emptyList(), fetcher);
}
public LoadData(Key sourceKey, List alternateKeys, DataFetcher fetcher) {
this.sourceKey = Preconditions.checkNotNull(sourceKey);
this.alternateKeys = Preconditions.checkNotNull(alternateKeys);
this.fetcher = Preconditions.checkNotNull(fetcher);
}
}
/**
* Returns a {@link com.bumptech.glide.load.model.ModelLoader.LoadData} containing a
* {@link com.bumptech.glide.load.data.DataFetcher} required to decode the resource
* represented by this model, as well as a set of {@link com.bumptech.glide.load.Key Keys} that
* identify the data loaded by the {@link com.bumptech.glide.load.data.DataFetcher} as well as an
* optional list of alternate keys from which equivalent data can be loaded. The
* {@link 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.
*
* @param model The model representing the resource.
* @param width The width in pixels of the view or target the resource will be loaded into, or
* {@link com.bumptech.glide.request.target.Target#SIZE_ORIGINAL} to indicate that
* the resource should be loaded at its original width.
* @param height The height in pixels of the view or target the resource will be loaded into, or
* {@link com.bumptech.glide.request.target.Target#SIZE_ORIGINAL} to indicate that
* the resource should be loaded at its original height.
*/
@Nullable
LoadData buildLoadData(Model model, int width, int height, Options options);
/**
* Returns true if the given model is a of a recognized type that this loader can probably load.
*
* 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. {@link ModelLoader ModelLoaders} that return true from this method may
* return {@code null} from {@link #buildLoadData(Object, int, int, Options)}
*/
boolean handles(Model model);
}