Qt多線程的實現
1.繼承QThread，重新run
2.繼承Object，調用moveToThread方法
兩種方法各有利弊：主要參考：http://blog.51cto.com/9291927/1879757
在這我主要記錄一點：不管是使用那種方式，要想在子線程里面觸發的信號的槽函數在子線程執行，信號槽連接必須使用DirectConnection 方式；
You won't see much of a difference unless you're working with objects having different thread affinities. Let's say you have QObjects A and B and they're both attached to different threads. Ahas a signal called somethingChanged() and B has a slot called handleChange().
If you use a direct connection
connect( A, SIGNAL(somethingChanged()), B, SLOT(handleChange()), Qt::DirectConnection );the method handleChange() will actually run in the A's thread. Basically, it's as if emitting the signal calls the slot method "directly". If B::handleChange() isn't thread-safe, this can cause some (difficult to locate) bugs. At the very least, you're missing out on the benefits of the extra thread.
If you change the connection method to Qt::QueuedConnection (or, in this case, let Qt decide which method to use), things get more interesting. Assuming B's thread is running an event loop, emitting the signal will post an event to B's event loop. The event loop queues the event, and eventually invokes the slot method whenever control returns to it (it being the event loop). This makes it pretty easy to deal with communication between/among threads in Qt (again, assuming your threads are running their own local event loops). You don't have to worry about locks, etc. because the event loop serializes the slot invocations.
Note: If you don't know how to change a QObject's thread affinity, look into QObject::moveToThread. That should get you started.
Edit
I should clarify my opening sentence. It does make a difference if you specify a queued connection - even for two objects on the same thread. The event is still posted to the thread's event loop. So, the method call is still asynchronous, meaning it can be delayed in unpredictable ways (depending on any other events the loop may need to process). However, if you don't specify a connection method, the direct method is automatically used for connections between objects on the same thread (at least it is in Qt 4.8).
https://stackoverflow.com/questions/15051553/qt-signals-queuedconnection-and-directconnection