1，信息数据的查询，删除使用AsycnQueryHandler处理
AsycnQueryHandler继承了Handler
public abstract class AsyncQueryHandler extends Handler
内部使用HandleThread来实现异步线程处理数据，成员变量也有一个Handler并拥有HandleThread的looper。
private Handler mWorkerThreadHandler;
public AsyncQueryHandler(ContentResolver cr) {
super();
mResolver = new WeakReference<ContentResolver>(cr);
synchronized (AsyncQueryHandler.class) {
if (sLooper == null) {
HandlerThread thread = new HandlerThread("AsyncQueryWorker");
thread.start();
sLooper = thread.getLooper();
}
}
mWorkerThreadHandler = createHandler(sLooper);
}
主线程调用AsycnQueryHandler的startQuery方法，成员变量mWorkerThreadHandler传递Message给HandleThread处理，查询参数使用对象WorkerArgs封装。
public void startQuery(int token, Object cookie, Uri uri,
String[] projection, String selection, String[] selectionArgs,
String orderBy) {
// Use the token as what so cancelOperations works properly
Message msg = mWorkerThreadHandler.obtainMessage(token);
msg.arg1 = EVENT_ARG_QUERY; WorkerArgs args = new WorkerArgs();
args.handler = this;
args.uri = uri;
args.projection = projection;
args.selection = selection;
args.selectionArgs = selectionArgs;
args.orderBy = orderBy;
args.cookie = cookie;
msg.obj = args; mWorkerThreadHandler.sendMessage(msg);
}
protected class WorkerHandler extends Handler {
public WorkerHandler(Looper looper) {
super(looper);
}
@Override
public void handleMessage(Message msg) {
final ContentResolver resolver = mResolver.get();
if (resolver == null) return;
WorkerArgs args = (WorkerArgs) msg.obj;
int token = msg.what;
int event = msg.arg1;
switch (event) {
case EVENT_ARG_QUERY:
Cursor cursor;
try {
cursor = resolver.query(args.uri, args.projection,
args.selection, args.selectionArgs,
args.orderBy);
// Calling getCount() causes the cursor window to be filled,
// which will make the first access on the main thread a lot faster.
if (cursor != null) {
cursor.getCount();
}
} catch (Exception e) {
Log.w(TAG, "Exception thrown during handling EVENT_ARG_QUERY", e);
cursor = null;
}
args.result = cursor;
break;
HandleThread将处理结果result封装到WorkerArgs中，再通过Message传递给AsycnQueryHandler, AsycnQueryHandler调用handleMessage就是主线程中处理了。
public void handleMessage(Message msg) {
WorkerArgs args = (WorkerArgs) msg.obj;
if (localLOGV) {
Log.d(TAG, "AsyncQueryHandler.handleMessage: msg.what=" + msg.what
+ ", msg.arg1=" + msg.arg1);
}
int token = msg.what;
int event = msg.arg1;
// pass token back to caller on each callback.
switch (event) {
case EVENT_ARG_QUERY:
onQueryComplete(token, args.cookie, (Cursor) args.result);
break;
2，对于信息数据加载后在UI中展现处理。
ConversationList中ConversationListItem布局时在XML中写好的，只需根据Conversation数据来显示或隐藏对应的view即可。
ComposeMessageActivity中的MessageListItem需要处理彩信附件，彩信附件有多种格式，且UI布局是从数据库中读取解析，所以无法直接在XML中写好，需要在代码中动态加载。也就是说对于彩信，需要同时处理UI加载(MessageListItem)和数据加载(MessageItem)。
MessageItem中使用了异步处理加载MMS数据。
private ItemLoadedFuture mItemLoadedFuture;
mItemLoadedFuture = MmsApp.getApplication().getPduLoaderManager()
.getPdu(mMessageUri, loadSlideshow,
new PduLoadedMessageItemCallback());
PduLoadManager是MMS源码中定义的异步处理类，使用了ThreadPoolExecutor来实现异步处理。getPdu方法中将处理结果封装为PduLoaded类通过PduLoadedMessageItemCallback接口回调将结果在主线程处理。
ItemLoadedFuture也是使用了接口回调的设计，回调方法setIsDone是在 PduLoadedMessageItemCallback中触发，但实现是在PduLoadManager中，所以主线程可以通过ItemLoadedFuture取消PduLoadManager中的Executor运行。
public class PduLoaderManager extends BackgroundLoaderManager
BackgroundLoaderManager(Context context) {
mPendingTaskUris = new HashSet<Uri>();
mCallbacks = new HashMap<Uri, Set<ItemLoadedCallback>>();
final LinkedBlockingQueue<Runnable> queue = new LinkedBlockingQueue<Runnable>();
final int poolSize = MAX_THREADS;
mExecutor = new ThreadPoolExecutor(
poolSize, poolSize, 5, TimeUnit.SECONDS, queue,
new BackgroundLoaderThreadFactory(getTag()));
mCallbackHandler = new Handler();
}
public ItemLoadedFuture getPdu(Uri uri, boolean requestSlideshow,
final ItemLoadedCallback<PduLoaded> callback) {
if (uri == null) {
throw new NullPointerException();
}
//……此处省略掉一些源码
//……为了显示不太长，便于查看
if (pduExists && slideshowExists) {
if (callbackRequired) {
PduLoaded pduLoaded = new PduLoaded(cacheEntry.getPdu(), slideshow);
callback.onItemLoaded(pduLoaded, null);
}//这几从缓存中返回数据
return new NullItemLoadedFuture();
} if (callbackRequired) {
addCallback(uri, callback);
} if (newTaskRequired) {
mPendingTaskUris.add(uri);
Runnable task = new PduTask(uri, requestSlideshow);
mExecutor.execute(task);//后台线程执行加载数据
}
return new ItemLoadedFuture() {//返回接口实现
private boolean mIsDone; public void cancel(Uri uri) {
cancelCallback(callback);
removePdu(uri); // the pdu and/or slideshow might be half loaded. Make sure
// we load fresh the next time this uri is requested.
} public void setIsDone(boolean done) {
cancelCallback(callback);
mIsDone = done;
} public boolean isDone() {
return mIsDone;
}
};
}
ItemLoadedFuture接口在MessageItem中声明，但在处理后台线程的类PduLoadManager中实现，可以实现主线程管理后台线程（如取消后台任务）
PduLoadedMessageItemCallback接口在MessageItem中实现，作为参数传递给PduLoadManager，将后台线程处理的结果result通过方法onItemLoaded(Object result, Throwable exception)返回到主线程处理。
MessageListItem中加载彩信附件
private void bindCommonMessage(final boolean sameItem) {
……
……
if (mMessageItem.mSlideshow == null) {//如果附件数据还未加载完成
final int mCurrentAttachmentType = mMessageItem.mAttachmentType;
mMessageItem.setOnPduLoaded(new MessageItem.PduLoadedCallback() {//这里又是接口回调实现
public void onPduLoaded(MessageItem messageItem) {
if (DEBUG) {
Log.v(TAG, "PduLoadedCallback in MessageListItem for item: " + mPosition +
" " + (mMessageItem == null ? "NULL" : mMessageItem.toString()) +
" passed in item: " +
(messageItem == null ? "NULL" : messageItem.toString()));
}
if (messageItem != null && mMessageItem != null &&
messageItem.getMessageId() == mMessageItem.getMessageId()) {
mMessageItem.setCachedFormattedMessage(null);
bindCommonMessage(//继续调用此方法，直到mMessageItem.mSlideshow加载完成
mCurrentAttachmentType == messageItem.mAttachmentType);
}
}
});
} else {
if (mPresenter == null) {
mPresenter = PresenterFactory.getPresenter(
"MmsThumbnailPresenter", mContext,
this, mMessageItem.mSlideshow);
} else {
mPresenter.setModel(mMessageItem.mSlideshow);
mPresenter.setView(this);
}
if (mImageLoadedCallback == null) {
mImageLoadedCallback = new ImageLoadedCallback(this);
} else {
mImageLoadedCallback.reset(this);
}
mPresenter.present(mImageLoadedCallback);
}
……
……
requestLayout();
}
3, 幻灯片编辑列表界面(SlideshowEditActivity)，幻灯片中视频缩略图加载处理。
SlideListAdapter的getView方法加载幻灯片缩略图
private View createViewFromResource(int position, View convertView, int resource) {
SlideListItemView slideListItemView;
slideListItemView = (SlideListItemView) mInflater.inflate(
resource, null);
// Show slide number.
TextView text;
text = (TextView) slideListItemView.findViewById(R.id.slide_number_text);
text.setText(mContext.getString(R.string.slide_number, position + 1));
SlideModel slide = getItem(position);
int dur = slide.getDuration() / 1000;
text = (TextView) slideListItemView.findViewById(R.id.duration_text);
text.setText(mContext.getResources().
getQuantityString(R.plurals.slide_duration, dur, dur));
if (mPresenter == null) {
mPresenter = PresenterFactory.getPresenter(
"SlideshowPresenter", mContext, slideListItemView, mSlideshow);
} else {
mPresenter.setModel(mSlideshow);
mPresenter.setView(slideListItemView);
}
((SlideshowPresenter) mPresenter).setLocation(position);
mPresenter.present(null);
return slideListItemView;
}
SlideshowPresenter中调用present(..)方法，针对视频类型使用了异步线程处理，避免耗时阻塞UI。也是用接口回调设计，
mItemLoadedFuture = video.loadThumbnailBitmap(mItemLoadedCallback, mLocation, mAdapterHandler);
mItemLoadedFuture的实现在ThumbnailManager中实现，ThumbnailManager也继承了BackgroundLoaderManager，还是使用Executor实现后台线程。
mItemLoadedCallback在SlideshowPresenter中实现，并传递给ThumbnailManager，用来将后台线程处理的结果返回到主线程处理。mItemLoadedCallback的回调方法处理返回的缩略图时，需要根据幻灯片的postion确定显示位置。但源码中，直接在SlideListAdapter的getView方法中设置positon,这样等视频缩率图返回时，position的值已经被修改了（因为getView在主线程中处理position, 而视频缩略图在异步线程中处理，当异步线程比主线程慢时，postion已经给后续处理改变了。）对于这个问题，可以将positon直接传给异步线程处理，缩率图显示时直接读取传递下去的postion，就不会被主线程的position影响。