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      1 /*
      2  * Copyright (C) 2013 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 
     17 package com.android.bitmap;
     18 
     19 import android.os.ParcelFileDescriptor;
     20 
     21 import java.io.IOException;
     22 import java.io.InputStream;
     23 
     24 /**
     25  * The decode task uses this class to get input to decode. You must implement at least one of
     26  * {@link #createFileDescriptorFactoryAsync(RequestKey, Callback)} or {@link #createInputStream()}.
     27  * {@link DecodeTask} will prioritize
     28  * {@link #createFileDescriptorFactoryAsync(RequestKey, Callback)} before falling back to
     29  * {@link #createInputStream()}.
     30  *
     31  * <p>
     32  * Clients of this interface must also implement {@link #equals(Object)} and {@link #hashCode()} as
     33  * this object will be used as a cache key.
     34  *
     35  * <p>
     36  * The following is a high level view of the interactions between RequestKey and the rest of the
     37  * system.
     38  *
     39  *       BasicBitmapDrawable
     40  *           UI Thread
     41  *              ++
     42  *       bind() ||            Background Thread
     43  *              |+-------------------->+
     44  *              || createFDFasync()   ||
     45  *              ||                    || Download from url
     46  *              ||                    || Cache on disk
     47  *              ||                    ||
     48  *              ||                    vv
     49  *              |<--------------------+x
     50  *              ||        FDFcreated()
     51  *              ||
     52  *              ||
     53  *              ||                DecodeTask
     54  *              ||             AsyncTask Thread
     55  *              |+-------------------->+
     56  *              || new().execute()    ||
     57  *              ||                    || Decode from FDF
     58  *              ||                    || or createInputStream()
     59  *              ||                    ||
     60  *              ||                    vv
     61  *              |<--------------------+x
     62  *              ||  onDecodeComplete()
     63  *              vv
     64  * invalidate() xx
     65  */
     66 public interface RequestKey {
     67 
     68     /**
     69      * Create an {@link FileDescriptorFactory} for a local file stored on the device and pass it to
     70      * the given callback. This method will be called first; if it returns null,
     71      * {@link #createInputStream()} will be called.
     72      *
     73      * Clients should implement this method if files are in the local cache folder, or if files must
     74      * be downloaded and cached.
     75      *
     76      * This method must be called from the UI thread.
     77      *
     78      * @param key      The key to create a FileDescriptorFactory for. This key will be passed to the
     79      *                 callback so it can check whether the key has changed.
     80      * @param callback The callback to notify once the FileDescriptorFactory has been created. Do
     81      *                 not invoke the callback directly from this method. Instead, create a handler
     82      *                 and post a Runnable.
     83      *
     84      * @return If the client will attempt to create a FileDescriptorFactory, return a Cancelable
     85      * object to cancel the asynchronous task. If the client wants to create an InputStream instead,
     86      * return null. The callback must be notified if and only if the client returns a Cancelable
     87      * object and not null.
     88      */
     89     public Cancelable createFileDescriptorFactoryAsync(RequestKey key, Callback callback);
     90 
     91     /**
     92      * Create an {@link InputStream} for the source. This method will be called if
     93      * {@link #createFileDescriptorFactoryAsync(RequestKey, Callback)} returns null.
     94      *
     95      * Clients should implement this method if files exist in the assets/ folder, or for prototypes
     96      * that open a connection directly on a URL (be warned that this will cause GCs).
     97      *
     98      * This method can be called from any thread.
     99      */
    100     public InputStream createInputStream() throws IOException;
    101 
    102     /**
    103      * Return true if the image source may have be oriented in either portrait or landscape, and
    104      * will need to be automatically re-oriented based on accompanying Exif metadata.
    105      *
    106      * This method can be called from any thread.
    107      */
    108     public boolean hasOrientationExif() throws IOException;
    109 
    110     /**
    111      * Callback for creating the {@link FileDescriptorFactory} asynchronously.
    112      */
    113     public interface Callback {
    114 
    115         /**
    116          * Notifies that the {@link FileDescriptorFactory} has been created. This must be called on
    117          * the UI thread.
    118          * @param key The key that the FileDescriptorFactory was created for. The callback should
    119          *            check that the key has not changed.
    120          * @param factory The FileDescriptorFactory to decode from.
    121          */
    122         void fileDescriptorFactoryCreated(RequestKey key, FileDescriptorFactory factory);
    123     }
    124 
    125     public interface FileDescriptorFactory {
    126         ParcelFileDescriptor createFileDescriptor();
    127     }
    128 
    129     /**
    130      * Interface for a background task that is cancelable.
    131      */
    132     public interface Cancelable {
    133 
    134         /**
    135          * Cancel the background task. This must be called on the UI thread.
    136          */
    137         void cancel();
    138     }
    139 }