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))
原文：http://www.cnblogs.com/senior-engineer/p/4865366.html
