Android5.1图库Gallery2代码分析数据加载流程

图片数据加载流程。

Gallery---->GalleryActivity------>AlbumSetPage------->AlbumPage--------->PhotoPage

                                              相册集                        照片集                 某张图片

1,AlbumSetPage.java

    private void initializeData(Bundle data) {

        String mediaPath = data.getString(AlbumSetPage.KEY_MEDIA_PATH);

        mMediaSet = mActivity.getDataManager().getMediaSet(mediaPath);

        mSelectionManager.setSourceMediaSet(mMediaSet);

        mAlbumSetDataAdapter = new AlbumSetDataLoader(

                mActivity, mMediaSet, DATA_CACHE_SIZE);

        mAlbumSetDataAdapter.setLoadingListener(new MyLoadingListener());

      }

增加回掉函数，当AlbumSetDataLoader.java发生变化时,更新界面。

2,AlbumSetDataloader.java

    public void resume() {

        mSource.addContentListener(mSourceListener);

        mReloadTask = new ReloadTask();

        mReloadTask.start();

增加回调函数，当数据库发生变化时，加载数据。

 

3,LocalAlbumSet.java (extends MediaSet)

    public void addContentListener(ContentListener listener) {

        /// M: [BUG.MODIFY] avoid ConcurrentModificationException @{

        /*mListeners.put(listener, null);*/

        synchronized(WEAK_HASH_MAP_LOCK) {

            mListeners.put(listener, null);

        }

   增加回调直接和数据库打交道。

4,DataManager.java

    public synchronized void initializeSourceMap() {

        if (!mSourceMap.isEmpty()) return;

        // the order matters, the UriSource must come last

        addSource(new LocalSource(mApplication));

新建LocalSource.java

 

5,LocalSource.java(extends MediaSource)

    @Override

    public MediaObject createMediaObject(Path path) {

        GalleryApp app = mApplication;

        switch (mMatcher.match(path)) {

            case LOCAL_ALL_ALBUMSET:

            case LOCAL_IMAGE_ALBUMSET:

            case LOCAL_VIDEO_ALBUMSET:

                return new LocalAlbumSet(path, mApplication);

新建LocalAlbumSet

 

6,LocalAlbumSet.java (extends MediaSet)

    public LocalAlbumSet(Path path, GalleryApp application) {

        super(path, nextVersionNumber());

        mApplication = application;

        mHandler = new Handler(application.getMainLooper());

        mType = getTypeFromPath(path);

        mNotifier = new ChangeNotifier(this, mWatchUris, application);

        mName = application.getResources().getString(

                R.string.set_label_local_albums);

    }

    private static final Uri[] mWatchUris =

        {Images.Media.EXTERNAL_CONTENT_URI, Video.Media.EXTERNAL_CONTENT_URI};

将监控要监控的图片和视频url添加到ChangeNotifier中。

 

7,ChangeNotifier.java

    public ChangeNotifier(MediaSet set, Uri[] uris, GalleryApp application) {

        mMediaSet = set;

        for (int i = 0; i < uris.length; i++) {

            application.getDataManager().registerChangeNotifier(uris[i], this);

   注册url。

 

8,DataManager.java

public void registerChangeNotifier(Uri uri, ChangeNotifier notifier) {

        NotifyBroker broker = null;

        synchronized (mNotifierMap) {

            broker = mNotifierMap.get(uri);

            if (broker == null) {

                broker = new NotifyBroker(mDefaultMainHandler);

                mApplication.getContentResolver()

                        .registerContentObserver(uri, true, broker);

                mNotifierMap.put(uri, broker);

            }

        }

        broker.registerNotifier(notifier);

}

将url和NotifyBroker进行关联，当url发生变化时，就调用回调类broker

9,DataManager.java

private static class NotifyBroker extends ContentObserver {

        @Override

        public synchronized void onChange(boolean selfChange) {

            for(ChangeNotifier notifier : mNotifiers.keySet()) {

                notifier.onChange(selfChange);

            }

        }

当url发生变化时，就调用。notifier.onChange(selfChange)

-----àmMediaSet.notifyContentChanged();(ChangeNotifier.java)

--à listener.onContentDirty();(LocalAlbumSet.java (extends MediaSet))