Android - Indeterminate ProgressBar

I am using the code from this website (http://www.helloandroid.com/tutorials/using-threads-and-progressdialog) in my App. It is somewhat working, but not entirely:

When I press Button X, a method is called, and while it is working, the progress bar is shown. After the method is done, another activity is started. So far everything is working fine. But when I press the "BACK" button on my phone, the progress bar is show开发者_如何转开发n again, and appears to be doing nothing.

What can I do to prevent that?

Dismiss the progress bar at the same time that you start the second activity.