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
     
      (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 BackgroundLoaderManagerBackgroundLoaderManager(Context context) {        mPendingTaskUris = new HashSet
     
      ();        mCallbacks = new HashMap
      
       >();        final LinkedBlockingQueue
       
         queue = new LinkedBlockingQueue
        
         ();        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
     
       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。