Programming with Android Network Operations Luca Bedogni Marco

Programming with Android: Network Operations Luca Bedogni Marco Di Felice Dipartimento di Scienze dell’Informazione Università di Bologna

Outline Network operations: Web. View and Web. Settings Network operations: HTTP Client Network operations: HTTP Requests Network operations: HTTP Responses Network operations: Download Manager Network operations: TCP/UDP Sockets Luca Bedogni, Marco Di Felice – Network programming with Android 2

Android: Web. View Usage Web. View A View that displays web pages, including simple browsing methods (history, zoom in/out/ search, etc). Implemented by the Web. View class public Web. View(Context contex) Main methods: Ø public void load. Url(String url) load the HTML page at url Ø public void load. Data(String data, String mime. Type, string encoding) load the HTML page contained in data Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 3

Android: Web. View Usage Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 4

Android: Web. View Usage By default, the Web. View UI does not include any navigation button …However, callbacks methods are defined: Ø public void go. Back() Ø public void go. Forward() Ø public void reload() Ø public void clear. History() Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 5

Android: Web. View Usage It is possible to modify the visualization options of a Web. View through the Web. Settings class. public Web. Settings get. Settings() Some options: Ø void set. Java. Script. Enabled(boolean) Ø void set. Build. In. Zoom. Controls(boolean) Ø void set. Default. Font. Size(int) Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 6

Android: Download Manager Download. Manager System service that handles long-run HTTP downloads. Ø The client can specify the file to be downloaded through an URI (path). Ø Download is conducted in background (with retries) Ø Broadcast Intent action is sent to notify when the download completes. Download. Manager dm=(Download. Manager) get. System. Service(DOWNLOAD_SERVICE); Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 7

Android: Download Manager Ø The Request class is used to specify a download request to the Download Manager. Request request=new Download. Manager. Request(Uri. parse(address)); Main methods of the Download. Manager Ø long enqueue(Download. Manager. Request) Ø Cursor query(Download. Manager. Query) Ø Parcel. File. Descriptor open. Downloaded. File(long) Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 8

Android: HTTP Classes HTTP (Hyper. Text Tranfer Protocol): Network protocol for exchange/transfer data (hypertext) Request/Resonse Communication Model MAIN COMMANDS Ø Ø Ø Ø HEAD GET POST PUT DELETE TRACE CONNECT Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 9

Android: HTTP (Abstract) Classes Ø Http. Client Interface for an HTTP client Ø Http. Request Interface for an HTTP request Ø Http. Response Interface for an HTTP response Ø Response. Handler<T> Handler that creates an object <T> from an HTTP Response Ø Http. Context of the HTTP Request (request+response+data) Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 10

Android: HTTP Classes Ø Http. Client Interface for an HTTP client (Default. Http. Client implementation of an Http. Client) Http. Client client=new Default. Http. Client(); Main method: The public method execute(…) performs an HTTP request, and allows to process an HTTP reply from the HTTP server. One of the signature of execute() abstract<T> T execute(Http. Uri. Request request, Response. Handler <T> response. Handler) Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 11

Android: HTTP Classes Ø Http. Request Interface for an HTTP request Two implementations: Http. Get implements the GET HTTP method Http. Get request=new Http. Get(String address); Http. Get request=new Http. Get(URI address); Http. Post Implements the POST HTTP method Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 12

Android: HTTP Classes Ø Response. Handler <T> Interface for creating an object <T> from an Http. Response, obtained after having executed an Http. Request. Method to override public abstract T handle. Response (Http. Response res) Generally, <T> is a String (HTML code) … Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 13

Android: HTTP Classes Ø Http. Post Implements the POST HTTP method Http. Post request=new Http. Post(String address); Http. Post request=new Http. Post(URI address); Encapsulating a parameter … List<Nome. Value. Pair> par=new Array. List<Nome. Value. Pair>() par. add(new Basic. Name. Value. Pair(“name”, ”Marco”); Http. Entity post. Entity=new Url. Encoded. Form. Entity(par); request. set. Entity(post. Entity); Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 14

Android: HTTP Classes Basic HTTPClient Request-Response Application … Http. Client client=new Default. Http. Client(); Http. Get request=new Http. Get(); request. set. URI(“http//www. cs. unibo. it”); try { client. execute(request, response. Handler); } catch (Client. Protocol. Exception e) { e. print. Stack. Trace(); } catch (IOException e) { e. print. Stack. Trace(); } Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 15

Android: HTTP Classes Basic HTTPClient Request-Response Application … class My. Response. Handler implements Response. Handler<String> { @Override public String handle. Response(Http. Response response) { Input. Stream content=response. get. Entity(). get. Content(); byte[] buffer=new byte[1024]; int num. Read=0; Byte. Array. Output. Stream stream=new Byte. Array. Output. Stream(); while ((num. Read=content. read(buffer))!=-1) stream. write(buffer, 0, num. Read); content. close(); String result=new String(stream. to. Byte. Array()); return result; } } Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 16

Android: TCP/IP Communication TCP/UDP Communication Android applications can use java. net. Socket facilities. Ø Use socket-based programming like in Java … Class Datagram. Socket UDP Socket Classes Socket/Server. Socket TCP socket Read/Write on Sockets through Input. Stream/Output. Stream Luca Bedogni, Marco Di Felice – Luca Bedogni 2012 Network programming with(c) Android 17