Make uiThreadHandler a static inner class.

Non-static inner classes as Handlers retain a reference to the activity
which can persist after the activity is destroyed, preventing it from
being garbage collected and using additional memory.

See https://groups.google.com/forum/?fromgroups=#!msg/android-developers/1aPZXZG6kWk/lIYDavGYn5UJ
Correct typo: allready -> already.