android - Implementing Oauth2 with login credentials from native login page -

i trying implement oauth2 based web service. have clientid, clientsecret, authorization endpoint, token endpoint , callback url(custom schema points android native page). when checked other oauth2 based apis, has login url , redirected login web page. in case there not login url, should redirected native login page , on success response should redirected logged in native page. how access token using oauth2? appreciated.

from comments above, let's assume have had asp.net webapi server-side app, , if android client app uses httpurlconnection, can refer following sample code (of course, need modify more make works requirement):

            string address = "http://<ip>:<port>/token";             httpurlconnection urlconnection;             string requestbody;             uri.builder builder = new uri.builder();             map<string, string> stringmap = new hashmap<>();             stringmap.put("grant_type", "password");             stringmap.put("username", "bnk");             stringmap.put("password", "bnk");              iterator entries = stringmap.entryset().iterator();             while (entries.hasnext()) {                 map.entry entry = (map.entry) entries.next();                 builder.appendqueryparameter(entry.getkey().tostring(), entry.getvalue().tostring());                 entries.remove();             }             requestbody = builder.build().getencodedquery();              try {                 url url = new url(address);                 urlconnection = (httpurlconnection) url.openconnection();                 urlconnection.setdoinput(true);                 urlconnection.setdooutput(true);                 urlconnection.setrequestmethod("post");                 urlconnection.setrequestproperty("content-type", "application/x-www-form-urlencoded");                 outputstream outputstream = new bufferedoutputstream(urlconnection.getoutputstream());                 bufferedwriter writer = new bufferedwriter(new outputstreamwriter(outputstream, "utf-8"));                 writer.write(requestbody);                 writer.flush();                 writer.close();                 outputstream.close();                 urlconnection.connect();                 if (urlconnection.getresponsecode() == httpurlconnection.http_ok) {                     // something...                 } else {                     // something...                 }                 // something...             } catch (exception e) {                 e.printstacktrace();             } 

update:

if prefer okhttp, please refer following working code:

    private class accesstokenrequest extends asynctask<void, void, string> {          @override         protected string doinbackground(void... voids) {             string accesstoken = null;             okhttpjsonrequest jsonrequest = new okhttpjsonrequest();             requestbody requestbody = new formencodingbuilder()                     .add("grant_type", "password")                     .add("username", "bnk")                     .add("password", "bnk123")                     .build();             try {                 jsonobject jsonobject = jsonrequest.post("http://192.168.1.100:24780/token", requestbody);                 if (!jsonobject.isnull("access_token")) {                     accesstoken = jsonobject.getstring("access_token");                                         }             } catch (ioexception | jsonexception e) {                 e.printstacktrace();             }             return accesstoken;         }          @override         protected void onpostexecute(string response) {             super.onpostexecute(response);             // such storing token furture requests         }     }      public class okhttpjsonrequest {         okhttpclient client = new okhttpclient();          jsonobject post(string url, requestbody body) throws ioexception, jsonexception {             request request = new request.builder()                     .url(url)                     .post(body)                     .build();             response response = client.newcall(request).execute();             return new jsonobject(response.body().string());         }     } 

hope helps!