android - NullPointerException: Google Spreadsheet, doInBackground -
i nullpointerexception , can't figure out what's wrong. i've tried bring necessary code. have 3 classes: mainactivity, googlecommunicator , customadapter. error caused following in customadapter:
mactivity.updatebought(position, "1"); the errors line 283 , 277 are:
283: url listfeedurl = mworksheet.getlistfeedurl(); 277: private class updatebought extends asynctask<void, void, string> the logcat:
3011-3026/com.example.andb.apop_l6_google_communicator_app e/androidruntime﹕ fatal exception: asynctask #1 process: com.example.andb.apop_l6_google_communicator_app, pid: 3011 java.lang.runtimeexception: error occured while executing doinbackground() @ android.os.asynctask$3.done(asynctask.java:300) @ java.util.concurrent.futuretask.finishcompletion(futuretask.java:355) @ java.util.concurrent.futuretask.setexception(futuretask.java:222) @ java.util.concurrent.futuretask.run(futuretask.java:242) @ android.os.asynctask$serialexecutor$1.run(asynctask.java:231) @ java.util.concurrent.threadpoolexecutor.runworker(threadpoolexecutor.java:1112) @ java.util.concurrent.threadpoolexecutor$worker.run(threadpoolexecutor.java:587) @ java.lang.thread.run(thread.java:818) caused by: java.lang.nullpointerexception: attempt invoke virtual method 'java.net.url com.google.gdata.data.spreadsheet.worksheetentry.getlistfeedurl()' on null object reference @ com.example.andb.apop_l6_google_communicator_app.googlecommunicator$updatebought.doinbackground(googlecommunicator.java:283) @ com.example.andb.apop_l6_google_communicator_app.googlecommunicator$updatebought.doinbackground(googlecommunicator.java:277) @ android.os.asynctask$2.call(asynctask.java:288) @ java.util.concurrent.futuretask.run(futuretask.java:237) @ android.os.asynctask$serialexecutor$1.run(asynctask.java:231) @ java.util.concurrent.threadpoolexecutor.runworker(threadpoolexecutor.java:1112) @ java.util.concurrent.threadpoolexecutor$worker.run(threadpoolexecutor.java:587)
mainactivity
public class mainactivity extends actionbaractivity implements adapterview.onitemclicklistener{ public googlecommunicator mgcom = new googlecommunicator(this,"torprode@gmail.com"); textview tvstatus; edittext etadd; @override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main); tvstatus = (textview) findviewbyid(r.id.tvstatus); dosomegooglestuff(); buttonlistener(); update(); } private void dosomegooglestuff(){ mgcom.setupfeed("mandatoryproject","buyme"); } private void drawlistview() { listadapter listadapter = new customadapter(this, mgcom.listitem, mgcom.listbought); listview listview = (listview) findviewbyid(r.id.lv_items); listview.setadapter(listadapter); } public void updatebought(int name, string bought) { mgcom.updatebought(name, bought); } @override public void onitemclick(adapterview<?> parent, view view, int position, long id) { } } googlecommunicator
public class googlecommunicator { //spreadsheet communication private static final string mscope = "oauth2:https://www.googleapis.com/auth/userinfo.profile https://spreadsheets.google.com/feeds https://docs.google.com/feeds"; private mainactivity mactivity; private spreadsheetservice mspreadsheetservice; private spreadsheetfeed mfeed; private string mspreadsheetname; private string mworksheetname; private spreadsheetentry mspreadsheet; private worksheetentry mworksheet; private string itemname; private int itemnameindex; private string itembought; //constructor public googlecommunicator(mainactivity activity, string email) { memail = email; mactivity = activity; //possibility callback method in activity class } //method called application. //creates instance of setupfeedtask (an asynctask) , executes public void setupfeed(string spreadsheet_name, string worksheet_name){ mspreadsheetname = spreadsheet_name; mworksheetname = worksheet_name; new setupfeedtask().execute(); } public void updatebought(int name, string bought) { itemnameindex = name; itembought = bought; new updatebought().execute(); } //asynctask handles network comminucation e.t.c. private class setupfeedtask extends asynctask<void, void, string> { //executes in own "worker thread" , doesnt block main ui thread @override protected string doinbackground(void... params) { // work mtoken = fetchtoken(); mspreadsheetservice = new spreadsheetservice("myspreadsheetservice"); mspreadsheetservice.setauthsubtoken(mtoken); url feed_url; try { feed_url = new url("https://spreadsheets.google.com/feeds/spreadsheets/private/full"); mfeed = mspreadsheetservice.getfeed(feed_url, spreadsheetfeed.class); }catch(malformedurlexception e){ //todo: handle exception log.v(tag, "malformedurlexception"); return null; }catch(serviceexception e){ //todo: handle exception log.v(tag, "serviceexception"); return null; }catch(ioexception e){ //todo: handle exception log.v(tag, "ioexception"); return null; } try{ list<spreadsheetentry> spreadsheets = mfeed.getentries(); // iterate through of spreadsheets returned (spreadsheetentry spreadsheet : spreadsheets) { if (spreadsheet.gettitle().getplaintext().equals(mspreadsheetname)) { list<worksheetentry> worksheets = spreadsheet.getworksheets(); //iterate through worksheets (worksheetentry worksheet : worksheets) { if (worksheet.gettitle().getplaintext().equals(mworksheetname)) { mspreadsheet = spreadsheet; mworksheet = worksheet; log.v(tag,"spreadsheet , worksheet setup."); } } } } }catch(serviceexception e){ //todo: handle exception log.v(tag, "service exception"); return null; }catch(ioexception e){ //todo: handle exception log.v(tag, "io exception"); return null; } //just example.. mtoken not important return return mtoken; } //call called when doinbackground has finished. //executes in main ui thread @override protected void onpostexecute(string result) { //todo: notify rest of application, e.g.: // * send broadcast // * send message handler // * call method on activity } //helper method private string fetchtoken(){ try { return googleauthutil.gettoken(mactivity, memail, mscope); } catch (userrecoverableauthexception userrecoverableexception) { // googleplayservices.apk either old, disabled, or not present, // recoverable, need show user ui through activity. //todo: if(mactivity instanceof mainactivity){ ((mainactivity)mactivity).handleexception(userrecoverableexception); if(d) log.e(tag,"userrecoverableauthexception"); } } catch (googleauthexception fatalexception) { //todo: //onerror("unrecoverable error " + fatalexception.getmessage(), fatalexception); if(d) log.e(tag,"googleauthexception"); } catch (ioexception ioexception){ if(d) log.e(tag,"ioexception"); } return null; } } private class updatebought extends asynctask<void, void, string> { @override protected string doinbackground(void... params) { try { url listfeedurl = mworksheet.getlistfeedurl(); listfeed listfeed = mspreadsheetservice.getfeed(listfeedurl, listfeed.class); listentry row = listfeed.getentries().get(itemnameindex); row.getcustomelements().setvaluelocal("bought", itembought); row.update(); } catch (ioexception e) { e.printstacktrace(); } catch (serviceexception e) { e.printstacktrace(); } return null; } } } customadapter
class customadapter extends arrayadapter<string> { arraylist boughtlist; mainactivity mactivity = new mainactivity(); customadapter(context context, arraylist<string> item, arraylist<string> bought) { super(context, r.layout.custom_listview, item); boughtlist = bought; } @override public view getview(final int position, view convertview, final viewgroup parent) { layoutinflater listviewinflater = (layoutinflater.from(getcontext())); final view customview = listviewinflater.inflate(r.layout.custom_listview, parent, false); final string fooditem = getitem(position); textview foodtext = (textview) customview.findviewbyid(r.id.tv_item); final checkbox checkbox = (checkbox) customview.findviewbyid(r.id.cb_checked); foodtext.settext(fooditem); string foodbought = string.valueof(boughtlist.get(position)); int foodboughtint = integer.parseint(foodbought); if (foodboughtint == 1) { checkbox.setchecked(true); } else { checkbox.setchecked(false); } checkbox.setoncheckedchangelistener(new compoundbutton.oncheckedchangelistener() { @override public void oncheckedchanged(compoundbutton buttonview, boolean ischecked) { if (checkbox.ischecked()) { system.out.println("jep"); mactivity.updatebought(position, "1"); } else { system.out.println("nope"); mactivity.updatebought(position, "0"); } } }); return customview; } }
you encountering race condition. have asynchronous tasks execute, , second asynchronous task depends on first task done work correctly. because both tasks done asynchronously, done in background, on separate threads. setupfeed method not done working, , start updatebought method on new thread. happens updatebought begins while mworksheet still null. have reorganize code logic avoid race condition. have done in past when have 2 async tasks put second asynchronous task in onpostexecute() of first async task, because onpostexecute occurs once doinbackground finished.
here execellent article on asynctasks , threads developer guides.
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