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      1 /*
      2  * Copyright (C) 2015 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 package com.android.messaging.datamodel.media;
     17 
     18 import java.util.List;
     19 
     20 /**
     21  * Keeps track of a media loading request. MediaResourceManager uses this interface to load, encode,
     22  * decode, and cache different types of media resource.
     23  *
     24  * This interface defines a media request class that's threading-model-blind. Wrapper classes
     25  * (such as {@link AsyncMediaRequestWrapper} wraps around any base media request to offer async
     26  * extensions).
     27  */
     28 public interface MediaRequest<T extends RefCountedMediaResource> {
     29     public static final int REQUEST_ENCODE_MEDIA = 1;
     30     public static final int REQUEST_DECODE_MEDIA = 2;
     31     public static final int REQUEST_LOAD_MEDIA = 3;
     32 
     33     /**
     34      * Returns a unique key used for storing and looking up the MediaRequest.
     35      */
     36     String getKey();
     37 
     38     /**
     39      * This method performs the heavy-lifting work of synchronously loading the media bytes for
     40      * this MediaRequest on a single threaded executor.
     41      * @param chainedTask subsequent tasks to be performed after this request is complete. For
     42      * example, an image request may need to compress the image resource before putting it in the
     43      * cache
     44      */
     45     T loadMediaBlocking(List<MediaRequest<T>> chainedTask) throws Exception;
     46 
     47     /**
     48      * Returns the media cache where this MediaRequest wants to store the loaded
     49      * media resource.
     50      */
     51     MediaCache<T> getMediaCache();
     52 
     53     /**
     54      * Returns the id of the cache where this MediaRequest wants to store the loaded
     55      * media resource.
     56      */
     57     int getCacheId();
     58 
     59     /**
     60      * Returns the request type of this media request, i.e. one of {@link #REQUEST_ENCODE_MEDIA},
     61      * {@link #REQUEST_DECODE_MEDIA}, or {@link #REQUEST_LOAD_MEDIA}. The default is
     62      * {@link #REQUEST_LOAD_MEDIA}
     63      */
     64     int getRequestType();
     65 
     66     /**
     67      * Returns the descriptor defining the request.
     68      */
     69     MediaRequestDescriptor<T> getDescriptor();
     70 }