Android  Networking  and    XML  Parsing  (SAX)  

Jussi  Pohjolainen  

URLConnec@on  1.  Obtain  a  new  HttpURLConnection  by  calling  

URL.openConnection()  and  cas@ng  the  result  to  HGpURLConnec@on.  

2.  Prepare  the  request.  (URI)  3.  Op@onally  upload  a  request  body  4.  Read  the  response.  Response  headers  typically  include  metadata  

such  as  the  response  body's  content  type  and  length,  modified  dates  and  session  cookies.  The  response  body  may  be  read  from  the  stream  returned  by  getInputStream().    

5.  Disconnect.  Once  the  response  body  has  been  read,  the  HttpURLConnection  should  be  closed  by  calling  disconnect().  Disconnec@ng  frees  all  resources  held  by  a  connec@on.  

Fetching  URL  URL url = new URL("http://www.somesite.fi");

HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

InputStream in = new BufferedInputStream(urlConnection.getInputStream());

String all = "";

int character;

while((character = stream.read()) != -1) {

all += (char) character;

}

urlConnection.disconnect();

Asynchronous  HGp  

•  It’s  wise  to  fetch  data  in  separate  thread  •  Standard  Java  threading  model  can  be  used,  but  touching  the  UI  thread  is  forbidden  in  Android  

•  To  update  UI  from  background  task,  you  need  Android  specific  classes  like  Handler.  

•  AsyncTask  is  a  class  that  wraps  threading  and  handling  UI  thread  in  the  same  class.  (Hold’s  Handler)  

AsyncTask  

AsyncTask  

Generic  Types  •  The  three  types  used  by  an  asynchronous  task  are  the  following:  1.   Params,  the  type  of  the  parameters  sent  to  the  task  

upon  execu@on.  2.   Progress,  the  type  of  the  progress  units  published  

during  the  background  computa@on.  3.   Result,  the  type  of  the  result  of  the  background  

computa@on.      private class MyTask extends AsyncTask<Void, Void, Void> { ... }  

SAX  

•  Standard  Java  SAX  parsing  or  android  api  wrappers  

Standard  Java  SAX  

Standard  Java  SAX