Presented by Roman Mazur

1. Android REST-client applications:
services approach
Sharing experience

2. Case

3. Case
New startup

4. Case
New startup

5. Case
New startup

6. Case
New startup

7. Case
New startup
stores
posts
sends
provides
notifies
suggests

8. Case
New startup
REST

9. REST
https://api.twitter.com/1/users/show.json?screen_name=roman_mazur
{
id : 14701612,
name : “Roman Mazur”,
location : “Ukraine, Kyiv”,
…
}

10. How to perform requests
@Override
public void onClick(View view) {
URLConnection connection
= new URL(…).openConnection();
…
}

11. How to perform requests
@Override
public void onClick(View view) {
URLConnection connection
= new URL(…).openConnection();
…
}

12. How to perform requests
• Obviously: not in the main (GUI) thread
• Using either URLConnection or HttpClient
– both have pros and cons
• Choose context: Activity vs. Service

13. Why not to use activities?
• User controls activity lifecycle
• When all your activities are in background
your process is a candidate for killing
• You’ll lose your data

14. Services Way
• See also
– Google IO 2010 session
“Developing Android REST Client Applications”

15. Services: our first implementation
Activity
1. onStart 4. performRequest
ApiMethodsSupport
(Helper for communication with service)
3. registerListener
2. bind 5. performRequest
(using binder)
Service
6. HTTP GET/POST/…

16. Services: our first implementation
• Main problem: rotations :)
– we register listener in onStart and remove it in
onStop
– what if response is received while we are rotating
the screen?

17. Current implementation
• Loaders!
– are awesome since they are not recreated in case
of configuration changes (at least in most cases)
• Custom loader
– binds to the service
– registers listener
– performs request
– gets the result
– unbinds

18. How we perform requests now
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
getLoaderManager().initLoader(1, null, this);
}

19. How we perform requests now
@Override
public Loader<ResponseData<Profile>>
onCreateLoader(int id, Bundle args) {
return
new SimpleRequestBuilder<Profile>(getActivity()) { }
.setUrl("https://api.twitter.com/1/users/show.json")
.addParam("screen_name", "TwitterAPI")
.getLoader();
}

20. How we perform requests now
@Override
public void
onLoadFinished(Loader<ResponseData<Profile>> loader,
ResponseData<Profile> data) {
if (data.isSuccessful()) {
Profile profile = data.getModel();
text1.setText(profile.getName());
text2.setText(profile.getDescription());
}
}

21. How we perform requests now
@Override
public void
onLoadFinished(Loader<ResponseData<Profile>> loader,
ResponseData<Profile> data) {
if (data.isSuccessful()) {
Profile profile = data.getModel();
text1.setText(profile.getName());
text2.setText(profile.getDescription());
}
}

22. ResponseData
• Result code
• Status message
• User visible message
• Data

23. Activity Side
• Request builder creates a request description
• Description is passed to a service
– a) as an Intent
– b) with a service binder method
performRequest

24. Service Side
• Either enqueues description processing or
performs it in the worker thread using
AsyncTask
• Request description builds URLConnection
• Input thread is read, parsed; result is analyzed
and then delivered to listeners

25. Service Side: Response Pipeline
URLConnection
ContentHandler
Parsed object
ResponseDataConverter
ResponseData
ContentAnalyzer Listeners
Analyzed
ResponseData

26. Conclusions
• Power
– requests processing can be easily managed
– requests can triggered by notifications and
AlarmManager
• Simplicity
– not much to learn if you are familiar with Android
loaders
• Caveats
– currently not everything is easy to customize

27. It’s open source
But we lack documentation :)
http://code.google.com/p/enroscar/
and we are preparing to release it on GitHub

28. Thanks!
Roman Mazur
Head of Android Unit at Stanfy
Kyiv GDD co-organizer
mazur.roman@gmail.com
+Roman Mazur
@roman_mazur