I'll start by presenting the activity class itself.
Next I'll discuss Androids Task Backstack which helps you to
easily navigate back and forth among the activities they use.
After that, I'll discuss the lifecycle of activities.
How they're created, executed, and terminated, and how Android manages and
communicates these lifecycle phases and changes to your applications.
After that, I'll discuss the APIs and
patterns that you'll need to programmatically start activities.
And finally, I'll finish up with a, with a discussion of
how Android activities handle device and application configuration changes.
As I said before, activities are the primary class for interacting with users.
They're designed to provide a visual interface through which the user can
interact with the application.
And by convention, activities should be modular, in the sense that, each activity
should support a single focused thing that the user can do with your application.
And individual things like viewing an email message or showing a log in screen.