Google Drive on android error: java.lang.IllegalArgumentException: the name must not be empty: null -

i got stuck "java.lang.illegalargumentexception: name must not empty: null" exception on google drive android app.

i have been googling several day without getting clue. code (an easy example) file list on google drive: (it taken here: google drive sdk exception)

import java.io.ioexception; import java.util.arraylist;  import android.accounts.account; import android.accounts.accountmanager; import android.app.activity; import android.app.progressdialog; import android.content.context; import android.content.dialoginterface; import android.content.intent; import android.os.asynctask; import android.os.bundle; import android.util.log; import android.view.view; import android.widget.button;  import com.google.android.gms.auth.googleauthexception; import com.google.android.gms.auth.googleauthutil; import com.google.android.gms.auth.userrecoverableauthexception; import com.google.android.gms.common.accountpicker; import com.google.api.client.auth.oauth2.bearertoken; import com.google.api.client.auth.oauth2.credential; import com.google.api.client.extensions.android.http.androidhttp; import     com.google.api.client.googleapis.extensions.android.accounts.googleaccountmanager; import com.google.api.client.googleapis.extensions.android.gms.auth.googleaccountcredential; import com.google.api.client.http.httprequestfactory; import com.google.api.client.http.httptransport; import com.google.api.client.http.json.jsonhttprequest; import com.google.api.client.http.json.jsonhttprequestinitializer; import com.google.api.client.json.jackson.jacksonfactory; import com.google.api.services.drive.drive; import com.google.api.services.drive.drive.files; import com.google.api.services.drive.driverequest; import com.google.api.services.drive.drivescopes; import com.google.api.services.drive.model.file; import com.google.api.services.drive.model.filelist; import com.maiko.xscanpet.r; import com.maiko.xscanpet.cloud.gdrivehelper;  public class fool_5 extends activity { private static final int choose_account=0; private static string accountname; private static int request_token=0; private button btn_drive; private context ctx = this; private activity = this;  googleaccountcredential mcredential= null;  public void oncreate(bundle savedinstancestate) {      super.oncreate(savedinstancestate);     // set gui layout     setcontentview(r.layout.fool_5);     // set variables access gui controls     btn_drive = (button) findviewbyid(r.id.btn_drive);         btn_drive.setonclicklistener(new view.onclicklistener() {         public void onclick(view v) {             chooseaccount();         }         }); }  public void chooseaccount() {     intent intent = accountpicker.newchooseaccountintent(null, null, new string[]{"com.google"}, false, null, null, null, null);     startactivityforresult(intent, choose_account); }  // fetch access token asynchronously. void getanduseauthtokeninasynctask(account account) {     asynctask<account, string, string> task = new asynctask<account, string, string>() {         progressdialog progressdlg;         asynctask<account, string, string> me = this;          @override         protected void onpreexecute() {             progressdlg = new progressdialog(ctx, progressdialog.style_spinner);             progressdlg.setmax(100);             progressdlg.settitle("validating...");             progressdlg.setmessage("verifying login data entered...\n\nthis action time out after 10 seconds.");             progressdlg.setcancelable(false);             progressdlg.setindeterminate(false);             progressdlg.setoncancellistener(new android.content.dialoginterface.oncancellistener() {                 public void oncancel(dialoginterface d) {                     progressdlg.dismiss();                     me.cancel(true);                 }             });             progressdlg.show();         }          @override         protected string doinbackground(account... params) {             return getaccesstoken(params[0]);         }          @override         protected void onpostexecute(string s) {             if (s == null) {                 // wait intent             } else {                 accountname = s;                 getdrivefiles();             }             progressdlg.dismiss();         }     };     task.execute(account); }  /**  * fetches token particular google account chosen user.  not run directly.  must run asynchronously inside asynctask.  * @param activity  * @param account  * @return  */ private string getaccesstoken(account account) {     try {         return googleauthutil.gettoken(ctx, account.name, "oauth2:" + drivescopes.drive);  // important: drivescopes must changed depending on level of access want     } catch (userrecoverableauthexception e) {         // start approval screen intent, if not run activity, add intent.flag_activity_new_task flag.         a.startactivityforresult(e.getintent(), request_token);         e.printstacktrace();         return null;     } catch (googleauthexception e) {         e.printstacktrace();         return null;     } catch (ioexception e) {         e.printstacktrace();         return null;     } }  private drive getdriveservice() {     mcredential = googleaccountcredential.usingoauth2(this, drivescopes.drive);     mcredential.setselectedaccountname(accountname);     return gdrivehelper.getdriveservice(mcredential,getresources().getstring(r.string.app_name));  }  /**  * obtains list of files on signed-in user's google drive account.  */ private void getdrivefiles() {     thread t = new thread(new runnable() {         @override         public void run() {             drive service = getdriveservice();             log.d("sitetrack", "function getdrivefiles()");             files.list request;             try {                 request = service.files().list(); // .setq("mimetype=\"text/plain\"");             } catch (ioexception e) {                   e.printstacktrace();                 return;             }             {                 filelist files;                 try {                     system.out.println("got here");                     log.d("sitetrack", request.tostring());                     //mcredential.setselectedaccountname(accountname);                     files = request.execute();                  } catch (ioexception e) {                     e.printstacktrace();                     log.d("sitetrack", "exception");                     return;                 }                 arraylist<file> filelist = (arraylist<file>) files.getitems();                 log.d("sitetrack", "files found: " + files.getitems().size());                 (file f : filelist) {                     string fileid = f.getid();                     string title = f.gettitle();                     log.d("sitetrack", "file " + fileid + ": " + title);                 }                 request.setpagetoken(files.getnextpagetoken());             } while (request.getpagetoken() != null && request.getpagetoken().length() >= 0);         }     });     t.start();  }  protected void onactivityresult(final int requestcode, final int resultcode, final intent data) {     if (requestcode == choose_account && resultcode == result_ok) {         accountname = data.getstringextra(accountmanager.key_account_name);         googleaccountmanager gam = new googleaccountmanager(this);         getanduseauthtokeninasynctask(gam.getaccountbyname(accountname));         log.d("sitetrack", "choose_account");     } else if (requestcode == request_token && resultcode == result_ok) {         accountname = data.getstringextra(accountmanager.key_account_name);         log.d("sitetrack", "request_token");     } }    } 

this generates trace on files = request.execute(); or request.execute():

04-20 01:40:26.105: e/androidruntime(27203): fatal exception: thread-39033 04-20 01:40:26.105: e/androidruntime(27203): java.lang.illegalargumentexception: name must not empty: null 04-20 01:40:26.105: e/androidruntime(27203):    @ android.os.parcel.readexception(parcel.java:1429) 04-20 01:40:26.105: e/androidruntime(27203):    @ android.os.parcel.readexception(parcel.java:1379) 04-20 01:40:26.105: e/androidruntime(27203):    @ com.google.android.gms.internal.x$a$a.a(unknown source) 04-20 01:40:26.105: e/androidruntime(27203):    @ com.google.android.gms.auth.googleauthutil.gettoken(unknown source) 04-20 01:40:26.105: e/androidruntime(27203):    @ com.google.android.gms.auth.googleauthutil.gettoken(unknown source) 04-20 01:40:26.105: e/androidruntime(27203):    @ com.google.api.client.googleapis.extensions.android.gms.auth.googleaccountcredential.gettoken(googleaccountcredential.java:192) 04-20 01:40:26.105: e/androidruntime(27203):    @ com.google.api.client.googleapis.extensions.android.gms.auth.googleaccountcredential$requesthandler.intercept(googleaccountcredential.java:217) 04-20 01:40:26.105: e/androidruntime(27203):    @ com.google.api.client.http.httprequest.execute(httprequest.java:888) 04-20 01:40:26.105: e/androidruntime(27203):    @ com.google.api.client.googleapis.services.abstractgoogleclientrequest.executeunparsed(abstractgoogleclientrequest.java:407) 04-20 01:40:26.105: e/androidruntime(27203):    @ com.google.api.client.googleapis.services.abstractgoogleclientrequest.executeunparsed(abstractgoogleclientrequest.java:340) 04-20 01:40:26.105: e/androidruntime(27203):    @ com.google.api.client.googleapis.services.abstractgoogleclientrequest.execute(abstractgoogleclientrequest.java:458) 04-20 01:40:26.105: e/androidruntime(27203):    @ com.maiko.fool.fool_5$3.run(fool_5.java:184) 04-20 01:40:26.105: e/androidruntime(27203):    @ java.lang.thread.run(thread.java:856) 

i feel lost this, without no clue wrong.i have followed tutorial configuring google api services: https://plus.google.com/u/0/114042449736049687152/posts/cd3l8zcjg5z

thank help.

verify var "accountname" passing "mcredential" object. thats reason of errors. greetings.