Enum ALooper 

pub enum ALooper {}

ALooper

A looper is the state tracking an event loop for a thread. Loopers do not define event structures or other such things; rather they are a lower-level facility to attach one or more discrete objects listening for an event. An “event” here is simply data available on a file descriptor: each attached object has an associated file descriptor, and waiting for “events” means (internally) polling on all of these file descriptors until one or more of them have data available.

A thread can have only one ALooper associated with it.