android app development 06 : network & web services
TRANSCRIPT
Network & Web ServicesAnuchit [email protected]
6
Licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
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
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.
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);
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).
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}
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();
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.
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) {
... }}
Workshop: Read text data from web
Read HTML data from web using HTTPConnection. See snippet in GitHub.
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);
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.
SOAP: Old fasion
Requester Provider
Yellow Pages
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.
WSDL
WSDL
WSDL
SOAP
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.
API Protocols
Ref: http://java.dzone.com/articles/streaming-apis-json-vs-xml-and
Data Formats
Ref: http://java.dzone.com/articles/streaming-apis-json-vs-xml-and
Say "Goodbye" to XML
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.
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.
HTTP Request
Client Server
HTTP Request
HTTP Response + Data
200 OK403 Forbidden404 Not found500 Internal Error
HTTP Request
Requester Provider
GET /users/anoochit HTTP/1.1
200 OK + Data
Example URI
● http://example.org/user/● http://example.org/user/anuchit● http://search.twitter.com/search.json?q=xxx
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
Mobile App with Web Services
Provider
Data Req
(2)Data
(1)Parse Res Data
http request
response
* This is your destiny you cannot change your future, accept using vendor sdk's
Call Web Services
Android RESTServer
200 OK with XML or JSON string
GET /user/anoochit
● Check request method● Parse data from URI● Process● Return XML or JSON string
● HTTP request● Method GET, POST, PUT or DELETE● Get BufferReader and pack into
"String" <= JSON String● Parse "String Key"● Get your value
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.
RESTful API Design
But you should follow design guideline● RESTful API Design● Learn REST
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
JSON Example
{ "firstname": "Anuchit", "lastname": "Chalothorn"}
JSON Example[ { "firstname" : "Anuchit", "lastname" : "Chalothorn" }, { "firstname" : "Sira", "lastname" : "Nokyongthong" }]
Android & JSON
JSON is a very condense data exchange format. Android includes the json.org libraries which allow to work easily with JSON files.
JSON Object Parsing
JSONObject c = new JSONObject(json);String firstname=c.get("firstname").toString();String lastname=c.get("lastname").toString();
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");}
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
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);
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"));
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; ...}
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
Call RESTful API
Android RESTServer
200 OK with XML or JSON string
GET /user/anoochit
● Check request method● Parse data from URI● Process● Return XML or JSON string
● HTTP request● Method GET, POST, PUT or DELETE● Get BufferReader and pack into
"String" <= JSON String● Parse "String Key"● Get your value
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
Workshop: RESTful Echo
$data = array("result"=> "Hello, ".$_POST["name"]);echo json_encode($data);
Workshop: RESTful Date Time
$data = array("result"=> date("d M Y H:i:s"));echo json_encode($data);
Workshop: RESTful Temperatureif ($_POST["type"]=="c") { $result=(($_POST["degree"]-32)*5)/9;} else { $result=(($_POST["degree"]*9)/5)+32;}$data = array("result"=>$result));echo json_encode($data);
Workshop: App REST Echo
Make a mobile app call REST Echo API using Http Post method to send value.
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.
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.
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