Android-Creating a Bound Service

When creating a service that provides binding, you must provide an 

IBinder

 that
provides the programming interface that clients can use to interact with the service. There are three ways you can define the interface:Extending
the Binder class，Using a Messenger，Using
AIDL。When you need to perform IPC, using a

Messenger

 for
your interface is simpler than implementing it with AIDL, because 

Messenger

 queues
all calls to the service, whereas, a pure AIDL interface sends simultaneous requests to the service, which must then handle multi-threading.