android app development 06 : network & web services

Network & Web ServicesAnuchit Chalothornanoochit@gmail.com

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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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