PanoramaMetadataLoader.java revision 8e963a5a6016d246184ed65906f9d103e92b17e2 
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
17package com.android.camera.data;
18
19import java.util.ArrayList;
20
21import android.content.Context;
22import android.net.Uri;
23
24import com.android.camera.util.PhotoSphereHelper;
25import com.android.camera.util.PhotoSphereHelper.PanoramaMetadata;
26
27/**
28 * This class breaks out the off-thread panorama support.
29 */
30public class PanoramaMetadataLoader {
31    /**
32     * Classes implementing this interface can get information about loaded
33     * photo sphere metadata.
34     */
35    public static interface PanoramaMetadataCallback {
36        /**
37         * Called with the loaded metadata or <code>null</code>.
38         */
39        public void onPanoramaMetadataLoaded(PanoramaMetadata metadata);
40    }
41
42    private PanoramaMetadata mPanoramaMetadata;
43    private ArrayList<PanoramaMetadataCallback> mCallbacksWaiting;
44    private Uri mMediaUri;
45
46    /**
47     * Instantiated the meta data loader for the image resource with the given
48     * URI.
49     */
50    public PanoramaMetadataLoader(Uri uri) {
51        mMediaUri = uri;
52    }
53
54    /**
55     * Asynchronously extract and return panorama metadata from the item with
56     * the given URI.
57     * <p>
58     * NOTE: This call is backed by a cache to speed up successive calls, which
59     * will return immediately. Use {@link #clearCachedValues()} is called.
60     */
61    public synchronized void getPanoramaMetadata(final Context context,
62            PanoramaMetadataCallback callback) {
63        if (mPanoramaMetadata != null) {
64            // Return the cached data right away, no need to fetch it again.
65            callback.onPanoramaMetadataLoaded(mPanoramaMetadata);
66        } else {
67            if (mCallbacksWaiting == null) {
68                mCallbacksWaiting = new ArrayList<PanoramaMetadataCallback>();
69
70                // TODO: Don't create a new thread each time, use a pool or
71                // single instance.
72                (new Thread() {
73                    @Override
74                    public void run() {
75                        onLoadingDone(PhotoSphereHelper.getPanoramaMetadata(context,
76                                mMediaUri));
77                    }
78                }).start();
79            }
80            mCallbacksWaiting.add(callback);
81        }
82    }
83
84    /**
85     * Clear cached value and stop all running loading threads.
86     */
87    public synchronized void clearCachedValues() {
88        if (mPanoramaMetadata != null) {
89            mPanoramaMetadata = null;
90        }
91
92        // TODO: Cancel running loading thread if active.
93     }
94
95    private synchronized void onLoadingDone(PanoramaMetadata metadata) {
96        mPanoramaMetadata = metadata;
97        if (mPanoramaMetadata == null) {
98            // Error getting panorama data from file. Treat as not panorama.
99            mPanoramaMetadata = PhotoSphereHelper.NOT_PANORAMA;
100        }
101        for (PanoramaMetadataCallback cb : mCallbacksWaiting) {
102            cb.onPanoramaMetadataLoaded(mPanoramaMetadata);
103        }
104        mCallbacksWaiting = null;
105    }
106}
107