1 package com.bumptech.glide.load.data; 2 3 import com.bumptech.glide.Priority; 4 import com.bumptech.glide.load.ResourceDecoder; 5 import com.bumptech.glide.load.model.ModelLoader; 6 7 /** 8 * A base class for lazily and retrieving data that can be used to load a resource. A new instance is created per image 9 * load by {@link ModelLoader}. {@link #loadData(Priority)} may or may not be called for any given load depending on 10 * whether or not the corresponding image is cached. Cancel also may or may not be called. If 11 * {@link #loadData(Priority)} is called, then so {@link #cleanup()} will be called. 12 * 13 * @param <T> The type of data to be loaded. 14 */ 15 public interface DataFetcher<T> { 16 17 /** 18 * Asynchronously fetch data from which a resource can be decoded. This will always be called on 19 * background thread so it is safe to perform long running tasks here. Any third party libraries called 20 * must be thread safe since this method will be called from a thread in a 21 * {@link java.util.concurrent.ExecutorService} that may have more than one background thread. 22 * 23 * This method will only be called when the corresponding image is not in the cache. 24 * 25 * @param priority The priority with which the request should be completed. 26 */ 27 public T loadData(Priority priority) throws Exception; 28 29 /** 30 * Cleanup or recycle any resources used by this data fetcher. This method will be called in a finally block 31 * after the data returned by {@link #loadData(Priority)} has been decoded by the {@link ResourceDecoder}. 32 */ 33 public void cleanup(); 34 35 /** 36 * Returns a string uniquely identifying the data that this fetcher will fetch including the specific size. 37 * 38 * <p> 39 * A hash of the bytes of the data that will be fetched is the ideal id but since that is in many cases 40 * impractical and not performant, urls, file paths, and uris are normally sufficient. 41 * </p> 42 */ 43 public String getId(); 44 45 /** 46 * A method that will be called when a load is no longer relevant and has been cancelled. This method does not need 47 * to guarantee that any in process loads do not finish. It also may be called before a load starts or after it 48 * finishes. 49 * 50 * <p> 51 * The best way to use this method is to cancel any loads that have not yet started, but allow those that are in 52 * process to finish since its we typically will want to display the same image in a different view in 53 * the near future. 54 * </p> 55 */ 56 public void cancel(); 57 } 58
