This document provides an overview of networking and web services for Android applications. It discusses connecting to networks, performing network operations on separate threads, using AsyncTask to run tasks asynchronously, checking network connectivity, reading data from web APIs, and calling RESTful web services. It also covers JSON and PHP for building simple RESTful APIs, with examples and workshops for making network requests and consuming REST APIs from an Android app.

1. 6
Network &
Web Services
Anuchit Chalothorn
anoochit@gmail.com
Licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

2. Connecting to Network
Note that to perform the network operations
described in this lesson, your application
manifest must include the following permissions:
<uses-permission android:name="android.permission.INTERNET"
/>
<uses-permission android:name="android.permission.
ACCESS_NETWORK_STATE"/>
Ref: http://developer.android.com/training/basics/network-ops/connecting.html

3. StrictMode
Within an Android application you should avoid
performing long running operations on the user
interface thread. This includes file and network
access. StrictMode allows to setup policies in
your application to avoid doing incorrect things.

4. Turn StrictMode Off
If you are targeting Android 3.0 or higher, you can turn this
check off via the following code at the beginning of your
onCreate() method of your Activity. (Not recommend)
StrictMode.ThreadPolicy policy = new StrictMode.
ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);

5. Manage Network Usage
A device can have various types of network connections.
This lesson focuses on using either a Wi-Fi or a mobile
network connection. To check the network connection, you
typically use the following classes:
● ConnectivityManager: Answers queries about the state of
network connectivity. It also notifies applications when
network connectivity changes.
● NetworkInfo: Describes the status of a network interface of a
given type (currently either Mobile or Wi-Fi).

6. Check the Network Connection
ConnectivityManager connMgr = (ConnectivityManager)
getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo=connMgr.getActiveNetworkInfo();
if (networkInfo != null && networkInfo.isConnected()){
// fetch data
} else {
// display error
}

7. Workshop: Check network connection
Use snippet from previous slide to check
network connection and notify user.
ConnectivityManager connMgr = (ConnectivityManager)
getSystemService(CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connMgr.
getActiveNetworkInfo();

9. Network Operations on a Separate Thread
Network operations can involve unpredictable
delays. To prevent this from causing a poor
user experience, always perform network
operations on a separate thread from the UI.
The AsyncTask class provides one of the
simplest ways to fire off a new task from the UI
thread.

10. AsyncTask
The AsyncTask class provides one of the
simplest ways to fire off a new task from the UI
thread.
private class DownloadWebpageText extends AsyncTask {
protected String doInBackground(String... urls) {
...
}
}

11. Workshop: Read text data from web
Read HTML data from web using
HTTPConnection. See snippet in GitHub.

14. Workshop: Load Image from Web
Read stream binary from web and pass into
ImageView
InputStream in = new URL(url).openStream();
myImage = BitmapFactory.decodeStream(in);
imageView.setImageBitmap(myImage);

16. Web Services
A web service is a method of communication
between two electronic devices over the World
Wide Web. We can identify two major classes
of Web services
● REST-compliant Web services
● arbitrary Web services.

17. SOAP: Old fasion
Yellow Pages WSDL
WSDL
WSDL
Requester Provider
SOAP
Requester ask or search yellow pages which address and how to talk with provider. The yellow pages
'll send the response by using WSDL how to talk which provide by Provider to the requester.
Requester receives the address and methods then communicate with Provider.

18. Web APIs
A web API is a development in web services
where emphasis has been moving to simpler
representational state transfer (REST) based
communications. RESTful APIs do not require
XML-based web service protocols (SOAP and
WSDL) to support their light-weight interfaces.

19. API Protocols
Ref: http://java.dzone.com/articles/streaming-apis-json-vs-xml-and

20. Data Formats
Ref: http://java.dzone.com/articles/streaming-apis-json-vs-xml-and

21. Say "Goodbye" to XML

22. RESTFul / REST API
a style of software architecture for distributed
systems such as the WWW. The REST
language uses nouns and verbs, and has an
emphasis on readability. Unlike SOAP, REST
does not require XML parsing and does not
require a message header to and from a
service provider.

23. Concept
● the base URI for the web service, such as
http://example.com/resources/
● the Internet media type of the data
supported by the web service.
● the set of operations supported by the web
service using HTTP methods (e.g., GET,
PUT, POST, or DELETE).
● The API must be hypertext driven.

24. HTTP Request
HTTP Request
Client Server
HTTP Response + Data
200 OK
403 Forbidden
404 Not found
500 Internal Error

25. HTTP Request
GET /users/anoochit HTTP/1.1
Requester Provider
200 OK + Data

26. Example URI
● http://example.org/user/
● http://example.org/user/anuchit
● http://search.twitter.com/search.json?q=xxx

27. Request & Action
Resource GET PUT POST DELETE
http://example.org/user list collection replace create delete
http://example.org/user/rose list data replace/ create ? / create delete

28. Mobile App with Web Services
http request
Data Req
Provider
(2) (1)
Data Parse Res Data
response
* This is your destiny you cannot change your future, accept using vendor sdk's

29. Call Web Services
GET /user/anoochit
REST
Android
Server
200 OK with XML or JSON string
● HTTP request ● Check request method
● Method GET, POST, PUT or DELETE ● Parse data from URI
● Get BufferReader and pack into ● Process
"String" <= JSON String ● Return XML or JSON string
● Parse "String Key"
● Get your value

30. No "official" standard
There is no "official" standard for RESTful web
services, This is because REST is an
architectural style, unlike SOAP, which is a
protocol. Even though REST is not a standard,
a RESTful implementation such as the Web
can use standards like HTTP, URI, XML, etc.

31. RESTful API Design
But you should follow design guideline
● RESTful API Design
● Learn REST

32. Useful tools
if you want to test your RESTful web service by
sent another method, try this
● Advanced REST Client for Chrome
● JSONView and JSONLint for Chrome
● REST Client for Firefox

33. JSON Example
{
"firstname": "Anuchit",
"lastname": "Chalothorn"
}

34. JSON Example
[
{
"firstname" : "Anuchit",
"lastname" : "Chalothorn"
},
{
"firstname" : "Sira",
"lastname" : "Nokyongthong"
}
]

35. Android & JSON
JSON is a very condense data exchange
format. Android includes the json.org libraries
which allow to work easily with JSON files.

36. JSON Object Parsing
JSONObject c = new JSONObject(json);
String firstname=c.get("firstname").toString();
String lastname=c.get("lastname").toString();

38. JSON Array Parsing
JSONArray data = new JSONArray(json);
for (int i = 0; i < data.length(); i++) {
JSONObject c = data.getJSONObject(i);
String firstname = c.getString("firstname");
String lastname = c.getString("lastname");
}

40. Simple RESTful with PHP
You can make a simple RESTful API with PHP
for routing, process and response JSON data.
The following tools you should have;
● Web Server with PHP support
● PHP Editor
● REST Client plugin for browser

41. Workshop: JSON with PHP
PHP has a function json_encode to generate
JSON data from mix value. Create an App to
read JSON data in a web server.
header('Content-Type: application/json;
charset=utf-8');
$data = array("msg"=>"Hello World JSON");
echo json_encode($data);

43. Workshop: JSON with PHP
Create multi-dimensional array the pass to json
function to make a JSON Array data
$data=array(
array("firstname"=>"Anuchit",
"lastname"=>"Chalothorn"),
array("firstname"=>"Sira",
"lastname"=>"Nokyongthong")
);

45. Workshop: Check request methods
PHP has $_SERVER variable to check HTTP
request methods of each request from client, so
you can check request from this variable.
$method = $_SERVER["REQUEST_METHOD"];
switch($method){
case "GET":
break;
...
}

47. RESTful Design
Now we can check request from client, now we
can follow the RESTful design guideline. You
may use htaccess to make a beautiful URL.
http://hostname/v1/contact/data
service version number resource data

48. Call RESTful API
GET /user/anoochit
REST
Android
Server
200 OK with XML or JSON string
● HTTP request ● Check request method
● Method GET, POST, PUT or DELETE ● Parse data from URI
● Get BufferReader and pack into ● Process
"String" <= JSON String ● Return XML or JSON string
● Parse "String Key"
● Get your value

49. Workshop: Simple RESTful
Make RESTful service of this
● Echo your name
○ sent your name with POST method and response
with JSON result
● Asking for date and time
○ sent GET method response with JSON result
● Temperature unit converter
○ sent a degree number and type of unit with
POST method and response JSON result

50. Workshop: RESTful Echo
$data = array("result"=>
"Hello, ".$_POST["name"]);
echo json_encode($data);

51. Workshop: RESTful Date Time
$data = array("result"=>
date("d M Y H:i:s"));
echo json_encode($data);

52. Workshop: RESTful Temperature
if ($_POST["type"]=="c") {
$result=(($_POST["degree"]-32)*5)/9;
} else {
$result=(($_POST["degree"]*9)/5)+32;
}
$data = array("result"=>$result));
echo json_encode($data);

53. Workshop: App REST Echo
Make a mobile app call REST Echo API using
Http Post method to send value.

55. Workshop: App REST Temperature
Make a mobile app call REST temperature unit
converter API, using Http Post method to send
a degree value and unit type to convert.

57. Workshop: App REST Date Time
Make a mobile app call REST date time, using
Http Get method to get a value of date and
time.

59. End