Android: Is each UI thread in an Activity a separate threads?

In an Android app with multiple Activities, is each activity's UI thread a separate thread or are they actuall开发者_StackOverflow中文版y the same thread (like a global, per app UI thread)?

Each application has one UI thread, which is used to run whichever Activity is in the foreground.

There is some more information here:

http://developer.android.com/guide/topics/fundamentals/processes-and-threads.html

http://android-developers.blogspot.co.il/2009/05/painless-threading.html

No, Android app have only one UI thread for all Activities.