Google Analytics in Android app - dealing with multiple activities

I was pretty excited to see how easy it is to set up Google Analytics with my app, but the lack of documentation has me sitting with a few questions. The only information that I can find is right from the documentation here , which only looks at reporting PageViews and Events from one Activity. I want to report PageViews and Events across multiple Activities in my app.

Why serve 1x1 pixel GIF (web bugs) data at all?

Many analytic and tracking tools are requesting 1x1 GIF image (web bug, invisible for the user) for cross-domain event storing/processing.

Why serve 1x1 pixel GIF (web bugs) data at all?

Many analytic and tracking tools are requesting 1x1 GIF image (web bug, invisible for the user) for cross-domain event storing/processing.

Track campaigns with Google Analytics without query string parameters?

Is there a supported way in Google Analytics to track a campaign without having to use query string parameters.

Google Analytics pageTracker is not defined?

Little bit confused... I am trying to track mailto links being clicked, but constantly 'pageTracker is not defined' is shown. I have the following code just before my end body tag ()

Google Analytics unique purchases suddenly stopped working

For some reason reporting of unique purchases has stopped working in google analytics for the past few days.