Modified example from Marakana. Using AIDL Service to authenticate username and password

1. AIDL - Services and IPC

2. Inter Process Communication

3. The caller invokes
Proxy. Proxy inturn
binds the current
activity to the
remote service
This is the Remote
method. It is exposed
as a Bound Service

4. droid Services - Basics
ervice is an application component that can perform long­running operations in th
kground and does not provide a user interface.
ervice can essentially take two forms:
rted : A service is "started" when a component (such as an activity) starts it by
ing startService(). For example, it might download or upload a file over the networ
und : A service is "bound" when an application component binds to it by calling
dService(). A bound service offers a client­server interface that allows components
nteract with the service, send requests, get results, and even do so across
cesses with interprocess communication (IPC).

5. droid Services – Basics
reate a service, you must create a subclass of Service .
back methods you should override are:
nd() : The system calls this method when another component wants to bind with t
ice (such as to perform RPC), by calling bindService().
you must provide an interface that clients use to communicate with the service
eturning an IBinder.
reate() : The system calls this method when the service is first created, to perform
­time setup procedures (before it calls either onStartCommand() or onBind()).
estroy() : The system calls this method when the service is no longer used and is
g destroyed.

6. IDL – Android Interface Definition Language
DL (Android Interface Definition Language) allows you to define the
ogramming interface that both the client and service use to communicate using
Android, one process cannot normally access the memory of another process.
to talk, they need to decompose their objects into primitives that the
erating system can understand, and marshall the objects across that boundary
you.

7. vice Life Cycle

8. ypical Use Case

9. xample
ACTIVITY
Username, password
Activity
User details
Activity
Activity
Remote
Service

10. teps
Create the .aidl file : This file defines the interface with method
signatures.
Implement the interface : The Android SDK tools generate an
interface based on your .aidl file.
This interface has an inner abstract class named Stub that extends
Binder and implements methods from your AIDL interface. You mus
extend the Stub class and implement the methods.
Expose the interface to clients : Implement a Service and override
onBind() to return your implementation of the Stub class.

11. Creating a .aidl file
// Declare the interface. – IUserInfoService.aidl
interface IUserInfoService {
String getInfo(in String user, in String pass);
}
hen you build your application, the SDK tools generate a .java interface file named after your .aidl
e.
he generated interface IUserInfoService contains inner class Stub ­ IUserInfoService.Stub

12. . Implementing the interface
eed to extend this class IUserInfoService.Stub by providing additional methods
return new IUserInfoService.Stub() {
@Override
public String getInfo(String user, String pass) throws RemoteException {
// TODO Auto­generated method stub
if (user.equals("arvind")) return "Welcome Arvind! You have 15 unread messages";
return user+pass;
}

13. Exposing your interface in Service class
e you've implemented the interface for your service,
need to expose it to clients so they can bind to it.
// UserInfoService
public IBinder onBind(Intent intent) {
return new IUserInfoService.Stub() {
@Override
public String getInfo(String user, String pass) throws RemoteException {
// TODO Auto­generated method stub
if (user.equals("arvind")) return "Welcome Arvind! You have 15 unread messages";
return user+pass;
}
};

14. ccessing Service in Activity
Use ServiceConnection class
�
onServiceConnected gives reference to service interface
service = IUserInfoService.Stub.asInterface((IBinder) boundService
Access the methods of service
service.getUserInfo(“….”,”….”);

15. dditional Info
The bindService() method returns immediately without a
value, but when the Android system creates the connection
between the client and service, it calls onServiceConnected(
on the ServiceConnection, to deliver the IBinder that the clie
can use to communicate with the service.

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