This chapter has provided an overview of threading within Android applications. When an application is first launched in a process, the runtime system creates a main thread in which all subsequently launched application components run by default. The primary role of the main thread is to handle the user interface, so any time consuming tasks performed in that thread will give the appearance that the application has locked up. It is essential, therefore, that tasks likely to take time to complete be started in a separate thread.
Because the Android user interface toolkit is not thread-safe, changes to the user interface should not be made in any thread other than the main thread. Background tasks may be performed in a separate thread by subclassing the AsyncTask class and implementing the class methods to perform the task and update the user interface.
