com.bumptech.glide.load.data.DataFetcher Maven / Gradle / Ivy
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package com.bumptech.glide.load.data;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import com.bumptech.glide.Priority;
import com.bumptech.glide.load.DataSource;
/**
* Lazily retrieves data that can be used to load a resource.
*
* A new instance is
* created per resource load by {@link com.bumptech.glide.load.model.ModelLoader}. {@link
* #loadData(com.bumptech.glide.Priority, com.bumptech.glide.load.data.DataFetcher.DataCallback)}
* may or may not be called for any given load depending on whether or not the corresponding
* resource is cached. Cancel also may or may not be called. If
* {@link #loadData(com.bumptech.glide.Priority,
* com.bumptech.glide.load.data.DataFetcher.DataCallback)}} is called, then so {@link #cleanup()}
* will be called.
*
* @param The type of data to be loaded (InputStream, byte[], File etc).
*/
public interface DataFetcher {
/**
* Callback that must be called when data has been loaded and is available, or when the load
* fails.
*
* @param The type of data that will be loaded.
*/
interface DataCallback {
/**
* Called with the loaded data if the load succeeded, or with {@code null} if the load failed.
*/
void onDataReady(@Nullable T data);
/**
* Called when the load fails.
*
* @param e a non-null {@link Exception} indicating why the load failed.
*/
void onLoadFailed(Exception e);
}
/**
* Fetch data from which a resource can be decoded.
*
* This will always be called on background thread so it is safe to perform long running tasks
* here. Any third party libraries called must be thread safe (or move the work to another thread)
* since this method will be called from a thread in a
* {@link java.util.concurrent.ExecutorService}
* that may have more than one background thread.
*
* You MUST use the {@link DataCallback} once the request is complete.
*
* You are free to move the fetch work to another thread and call the callback from there.
*
* This method will only be called when the corresponding resource is not in the cache.
*
* Note - this method will be run on a background thread so blocking I/O is safe.
*
* @param priority The priority with which the request should be completed.
* @param callback The callback to use when the request is complete
* @see #cleanup() where the data retuned will be cleaned up
*/
void loadData(Priority priority, DataCallback callback);
/**
* Cleanup or recycle any resources used by this data fetcher. This method will be called in a
* finally block after the data provided by {@link #loadData(com.bumptech.glide.Priority,
* com.bumptech.glide.load.data.DataFetcher.DataCallback)} has been decoded by the
* {@link com.bumptech.glide.load.ResourceDecoder}.
*
* Note - this method will be run on a background thread so blocking I/O is safe.
*/
void cleanup();
/**
* A method that will be called when a load is no longer relevant and has been cancelled. This
* method does not need to guarantee that any in process loads do not finish. It also may be
* called before a load starts or after it finishes.
*
* The best way to use this method is to cancel any loads that have not yet started, but allow
* those that are in process to finish since its we typically will want to display the same
* resource in a different view in the near future.
*
* Note - this method will be run on the main thread so it should not perform blocking
* operations and should finish quickly.
*/
void cancel();
/**
* Returns the class of the data this fetcher will attempt to obtain.
*/
@NonNull
Class getDataClass();
/**
* Returns the {@link com.bumptech.glide.load.DataSource} this fetcher will return data from.
*/
@NonNull
DataSource getDataSource();
}