As the Tutorial on Android background processing with Handlers, AsyncTask and Loaders on the Vogella site puts it:
The Handler class can be used to register to a thread and provides a simple channel to send data to this thread.
The AsyncTask class encapsulates the creation of a background process and the synchronization with the main thread. It also supports reporting progress of the running tasks.
And a Thread is basically the core element of multithreading which a developer can use with the following disadvantage:
If you use Java threads you have to handle the following requirements
in your own code:
- Synchronization with the main thread if you post back results to the user interface
- No default for canceling the thread
- No default thread pooling
- No default for handling configuration changes in Android
And regarding the AsyncTask, as the Android Developer's Reference puts it:
AsyncTask enables proper and easy use of the UI thread. This class
allows to perform background operations and publish results on the UI
thread without having to manipulate threads and/or handlers.
AsyncTask is designed to be a helper class around Thread and Handler
and does not constitute a generic threading framework. AsyncTasks
should ideally be used for short operations (a few seconds at the
most.) If you need to keep threads running for long periods of time,
it is highly recommended you use the various APIs provided by the
java.util.concurrent package such as Executor, ThreadPoolExecutor and
FutureTask.
Update May 2015: I found an excellent series of lectures covering this topic.
This is the Google Search: Douglas Schmidt lecture android concurrency and synchronisation
This is the video of the first lecture on YouTube
All this is part of the CS 282 (2013): Systems Programming for Android from the Vanderbilt University. Here's the YouTube Playlist
Douglas Schmidt seems to be an excellent lecturer
Important: If you are at a point where you are considering to use AsyncTask to solve your threading issues, you should first check out ReactiveX/RxAndroid for a possibly more appropriate programming pattern. A very good resource for getting an overview is Learning RxJava 2 for Android by example.
