java - Async task crashing during doInBackground() -

i having problem android app i'm trying develo,apparently crushes when it's execute doinbackground,my logcat looks this:

08-19 04:40:57.046: d/request!(4766): starting 08-19 04:40:57.125: w/dalvikvm(4766): threadid=9: thread exiting uncaught exception (group=0x40018578) 08-19 04:40:57.132: e/androidruntime(4766): fatal exception: asynctask #1 08-19 04:40:57.132: e/androidruntime(4766): java.lang.runtimeexception: error occured while executing doinbackground() 08-19 04:40:57.132: e/androidruntime(4766):     @ android.os.asynctask$3.done(asynctask.java:200) 08-19 04:40:57.132: e/androidruntime(4766):     @ java.util.concurrent.futuretask$sync.innersetexception(futuretask.java:274) 08-19 04:40:57.132: e/androidruntime(4766):     @ java.util.concurrent.futuretask.setexception(futuretask.java:125) 08-19 04:40:57.132: e/androidruntime(4766):     @ java.util.concurrent.futuretask$sync.innerrun(futuretask.java:308) 08-19 04:40:57.132: e/androidruntime(4766):     @ java.util.concurrent.futuretask.run(futuretask.java:138) 08-19 04:40:57.132: e/androidruntime(4766):     @ java.util.concurrent.threadpoolexecutor.runworker(threadpoolexecutor.java:1088) 08-19 04:40:57.132: e/androidruntime(4766):     @ java.util.concurrent.threadpoolexecutor$worker.run(threadpoolexecutor.java:581) 08-19 04:40:57.132: e/androidruntime(4766):     @ java.lang.thread.run(thread.java:1019) 08-19 04:40:57.132: e/androidruntime(4766): caused by: java.lang.illegalstateexception: target host must not null, or set in parameters. 08-19 04:40:57.132: e/androidruntime(4766):     @ org.apache.http.impl.client.defaultrequestdirector.determineroute(defaultrequestdirector.java:577) 08-19 04:40:57.132: e/androidruntime(4766):     @ org.apache.http.impl.client.defaultrequestdirector.execute(defaultrequestdirector.java:292) 08-19 04:40:57.132: e/androidruntime(4766):     @ org.apache.http.impl.client.abstracthttpclient.execute(abstracthttpclient.java:555) 08-19 04:40:57.132: e/androidruntime(4766):     @ org.apache.http.impl.client.abstracthttpclient.execute(abstracthttpclient.java:487) 08-19 04:40:57.132: e/androidruntime(4766):     @ org.apache.http.impl.client.abstracthttpclient.execute(abstracthttpclient.java:465) 08-19 04:40:57.132: e/androidruntime(4766):     @ com.example.prova1.jsonparser.makehttprequest(jsonparser.java:110) 08-19 04:40:57.132: e/androidruntime(4766):     @ com.example.prova1.login$attemptlogin.doinbackground(login.java:159) 08-19 04:40:57.132: e/androidruntime(4766):     @ com.example.prova1.login$attemptlogin.doinbackground(login.java:1) 08-19 04:40:57.132: e/androidruntime(4766):     @ android.os.asynctask$2.call(asynctask.java:185) 08-19 04:40:57.132: e/androidruntime(4766):     @ java.util.concurrent.futuretask$sync.innerrun(futuretask.java:306) 08-19 04:40:57.132: e/androidruntime(4766):     ... 4 more 08-19 04:41:04.726: e/windowmanager(4766): activity com.example.prova1.login has leaked window com.android.internal.policy.impl.phonewindow$decorview@4054b1a8 added here 08-19 04:41:04.726: e/windowmanager(4766): android.view.windowleaked: activity com.example.prova1.login has leaked window com.android.internal.policy.impl.phonewindow$decorview@4054b1a8 added here 08-19 04:41:04.726: e/windowmanager(4766):  @ android.view.viewroot.<init>(viewroot.java:263) 08-19 04:41:04.726: e/windowmanager(4766):  @ android.view.windowmanagerimpl.addview(windowmanagerimpl.java:171) 08-19 04:41:04.726: e/windowmanager(4766):  @ android.view.windowmanagerimpl.addview(windowmanagerimpl.java:114) 08-19 04:41:04.726: e/windowmanager(4766):  @ android.view.window$localwindowmanager.addview(window.java:424) 08-19 04:41:04.726: e/windowmanager(4766):  @ android.app.dialog.show(dialog.java:241) 08-19 04:41:04.726: e/windowmanager(4766):  @ com.example.prova1.login$attemptlogin.onpreexecute(login.java:126) 08-19 04:41:04.726: e/windowmanager(4766):  @ android.os.asynctask.execute(asynctask.java:391) 08-19 04:41:04.726: e/windowmanager(4766):  @ com.example.prova1.login.onclick(login.java:93) 08-19 04:41:04.726: e/windowmanager(4766):  @ android.view.view.performclick(view.java:2485) 08-19 04:41:04.726: e/windowmanager(4766):  @ android.view.view$performclick.run(view.java:9080) 08-19 04:41:04.726: e/windowmanager(4766):  @ android.os.handler.handlecallback(handler.java:587) 08-19 04:41:04.726: e/windowmanager(4766):  @ android.os.handler.dispatchmessage(handler.java:92) 08-19 04:41:04.726: e/windowmanager(4766):  @ android.os.looper.loop(looper.java:130) 08-19 04:41:04.726: e/windowmanager(4766):  @ android.app.activitythread.main(activitythread.java:3687) 08-19 04:41:04.726: e/windowmanager(4766):  @ java.lang.reflect.method.invokenative(native method) 08-19 04:41:04.726: e/windowmanager(4766):  @ java.lang.reflect.method.invoke(method.java:507) 08-19 04:41:04.726: e/windowmanager(4766):  @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:867) 08-19 04:41:04.726: e/windowmanager(4766):  @ com.android.internal.os.zygoteinit.main(zygoteinit.java:625) 08-19 04:41:04.726: e/windowmanager(4766):  @ dalvik.system.nativestart.main(native method) 08-19 04:41:05.070: d/dalvikvm(4766): gc_concurrent freed 235k, 48% free 2955k/5639k, external 507k/517k, paused 3ms+3ms 

my java code this;

public class login extends activity implements onclicklistener{     private edittext user, pass;      private button msubmit, mregister;       // progress dialog     private progressdialog pdialog;      // json parser class      jsonparser jsonparser = new jsonparser();      //php login script location:      //localhost :     //testing on device      //put local ip instead,  on windows, run cmd > ipconfig     //or in mac's terminal type ifconfig , ip under en0 or en1        //testing on emulator:   private static final string login_url = "login_url";     //testing real server:       //json element ids repsonse of php script:      private static final string tag_success = "success";      private static final string tag_message = "message";        @override      protected void oncreate(bundle savedinstancestate) {          // todo auto-generated method stub         super.oncreate(savedinstancestate);          setcontentview(r.layout.activity_login);       //setup input fields          user = (edittext)findviewbyid(r.id.username);          pass = (edittext)findviewbyid(r.id.password);          //setup buttons          msubmit = (button)findviewbyid(r.id.button1);          mregister = (button)findviewbyid(r.id.button2);       //register listeners          msubmit.setonclicklistener(this);          mregister.setonclicklistener(this);   }      @override      public void onclick(view v) {          // todo auto-generated method stub         switch (v.getid()) {         case r.id.button1:                 new attemptlogin().execute();             break;         case r.id.button2:              intent = new intent(this, register.class);                  startactivity(i);             break;          default:             break;      }      }      class attemptlogin extends asynctask<string, string, string> {       /**            * */          boolean failure = false;          @override          protected void onpreexecute() {              super.onpreexecute();              pdialog = new progressdialog(login.this);              pdialog.setmessage("attempting login...");          pdialog.setindeterminate(false);          pdialog.setcancelable(true);         pdialog.show();          }     @override          protected string doinbackground(string... args) {              // todo auto-generated method stub               // check success tag              int success;               string username = user.gettext().tostring();//my app seems crushing here               string password = pass.gettext().tostring();              try {                  // building parameters                  list<namevaluepair> params = new arraylist<namevaluepair>();                  params.add(new basicnamevaluepair("username", username));                  params.add(new basicnamevaluepair("password", password));                  log.d("request!", "starting");                  // getting product details making http request                  jsonobject json = jsonparser.makehttprequest(                         login_url, "post", params);                    // check log json response                  log.d("login attempt", json.tostring());                    // json success tag                  success = json.getint(tag_success);                  if (success == 1) {                      log.d("login successful!", json.tostring());               intent = new intent(login.this, readcomments.class);                      finish();                      startactivity(i);                      return json.getstring(tag_message);                  }else{                      log.d("login failure!", json.getstring(tag_message));                      return json.getstring(tag_message);                  }              } catch (jsonexception e) {                  e.printstacktrace();              }              return null;          }          /**           * after completing background task dismiss progress dialog           * **/          protected void onpostexecute(string file_url) {              // dismiss dialog once product deleted              pdialog.dismiss();              if (file_url != null){                  toast.maketext(login.this, file_url, toast.length_long).show();              }          }      }  } 

any assistance highly appreciated!!

your log says:

target host must not null, or set in parameters.    

as has been pointed out, login_url may malformed. suggest log.v() , see yourself.