1. Introduction to Android
Google Cloud Messaging
Amrit Sanjeev
Organizer – Bangalore Android User Group

2. About me
• Android hacker.
• Organizer, Bangalore Android User
Group ( www.blrdroid.org )
• Research Engineer at Philips R&D

3. Bangalore Android User Group ( www.BlrDroid.org)
• Largest open Android developer community in
the country and second largest in the world.
• Over 2500 members
• 19 meetups
• 3 hackathons
• Active participation in events like Droidcon,
Global Android Developer hackathon etc

4. What we will be discussing today.
Why do we How it is
What is implemented ?
GCM? need GCM?
Google Cloud Messaging

5. What is GCM?
Google Cloud Messaging

6. GCM definition
GCM stands for Google Cloud Messaging .
It is a free service that allows developers to send
data from third party servers to their applications
running on android devices
Handles queuing of messages and delivery to the
target application running on the target device.
Intended use is not to send huge amount of data to
the client device

7. Things to keep in mind
Application on the android device DOES
NOT need to be running to receive
messages.
Requires user to set up a Google account
on the device.
It is purely a routing component
There is no guaranteed delivery of
messages to the device .

8. Focus of GCM
GCM stats are
Ease of use. No available through
No quotas.
sign-up forms. the Android
Developer Console.
Rich set of new
Battery efficiency.
APIs

9. Difference between GCM and C2DM
Simple API Key from Google
APIs console page.
Sender id is the project id rather
than email address
Supports data in JSON format
and plain text

10. Difference between GCM and C2DM
Multicast message support
Multiple senders
Messages have time to live ( 0 ~
4 weeks ) eg. Expiring invitations
Payload up to 4kb

11. Why do we need GCM?
The why part

12. The need to use GCM
Client server architecture is the most
common architecture .
Most application do all the heavy lifting and
processing at the servers and then use the
processed data within the applications .
Scalability & extensibility
More computing power

13. The need to use GCM
Background process polling server for
information at regular intervals is a bad
design
Battery performance
System resource usage ( memory , CPU )
Complicated coding
Application does not need to be running in
the background for receiving data messages.
Lower cost and better tracking than SMS.

14. The need to use GCM
Less coding required
Not need to worry about queuing of
messages
Differed delivery
Simpler application flow

15. The need to use GCM
In a nutshell it makes application design
much more simple, improves battery
performance and makes better use of
system resources .

16. How it is implemented?
The internals

17. Major components
Your application server
GCM servers
Mobile device

18. Typical sequence of events
The application
server sends a
message to GCM
servers.
Google queues
The Android
and stores the
application
message in case
processes the
the device is
message
offline.
On the device,
the system
When the device
broadcasts the
is online, Google
message to the
sends the
specified Android.
message to the
This wakes the
device.
Android
application up.

19. Minimum requirements ( device side )
Android 2.2 +
Android market place should be installed
Emulator with Google APIs
Internet connection
Google account ( device version < 4.0.4 )
.

20. Minimum requirements ( server side )
HTTPS application server that should be
Able to communicate with your client.
Able to fire off HTTP requests to the GCM
server.
Able to handle requests and queue data as
needed. For example, it should be able to
perform exponential back off.
Able to store the user device registration id .

21. Android application
Copy the Add a Wire it up
required broadcast in your
libs receiver activity
Make
Add an
changes
Intent
to the
service
manifest

22. Alternate Infrastructures
• Alternative to GCM is required under
following conditions
Limited connectivity to internet services
Security requirement
Guaranteed delivery
SLAs on delivery
No quota limits
• Downsides
Complicated design
Battery consumption on device is higher.

23. Thank you
In case you have more queries please feel free to contact
Amrit.sanjeev@gmail.com (+91 97407 44557 )
@amsanjeev

24. BACKUP SLIDES

25. Add required libs
Install Google Cloud Messaging for
android using SDK manager.
Copy gcm.jar from
YOUR_SDK_ROOT/extras/google/gcm-client/dist to
libs in your project folder

26. Changes to Manifest file
Add <use-sdk … >
Declare & use a custom permission
Add additional permissions
 internet
 get_accounts
 wake_lock

27. Write Intentservice
 subclass of
com.google.android.gcm.GCMBaseIntentService
 must contain a public constructor,
 Generally named my_app_package.GCMIntentService
 Override the following functions with appropriate logic
 onRegistered
 onUnRegistered
 onMessage
 onError
 onRecoverableError

28. Add boardcast receiver
 add a broadcast receiver with the custom
permissions and following actions
 <action android:name="com.google.android.c2dm.intent.RECEIVE" />
 <action android:name="com.google.android.c2dm.intent.REGISTRATION" />
Should be defined in the manifest and not
programmatically

29. Finally the activity
CheckDevice ()
CheckManifest()
getRegistrationId()
Register()