json - Android null pointer exception when using Async task -

-

i have async task in class , is parsing json. when execute code, in logcat see message: fatal exception: asynctask #1

.

.

.

caused by: java.lang.nullpointerexception.

if want @ it, here code:

mainactivity.java

    protected void oncreate(bundle savedinstancestate) {          super.oncreate(savedinstancestate);          setcontentview(r.layout.activity_main);           new readjson().execute(there address here);           textview = (textview) findviewbyid(r.id.textview1);    }     //async task:     inputstream inputstream = null;     string result = null;     httpresponse response;     bufferedreader reader;     jsonobject jobject;     string ajsonstring1;     string ajsonstring2;       public class readjson extends asynctask<string, void, string> {         protected string doinbackground(string... url) {              defaulthttpclient   httpclient = new defaulthttpclient(new basichttpparams());             httppost httppost = new httppost(there same address here);             // depends on web service             httppost.setheader("content-type", "application/json");              try {                 response = httpclient.execute(httppost);             } catch (clientprotocolexception e) {                 // todo auto-generated catch block                     e.printstacktrace();             } catch (ioexception e) {                 // todo auto-generated catch block                 e.printstacktrace();             }                        httpentity entity = response.getentity();              try {                 inputstream = entity.getcontent();             } catch (illegalstateexception e) {                 // todo auto-generated catch block                 e.printstacktrace();             } catch (ioexception e) {                 // todo auto-generated catch block                 e.printstacktrace();             }             // json utf-8 default beleive              try {                 reader = new bufferedreader(new inputstreamreader(inputstream, "utf-8"), 8);             } catch (unsupportedencodingexception e) {                 // todo auto-generated catch block                 e.printstacktrace();             }             stringbuilder sb = new stringbuilder();              string line = null;             try {                 while ((line = reader.readline()) != null)                 {                     sb.append(line + "\n");                 }             } catch (ioexception e) {                 // todo auto-generated catch block                 e.printstacktrace();             }             result = sb.tostring();                try {                 jobject = new jsonobject(result);             } catch (jsonexception e) {                 // todo auto-generated catch block                 e.printstacktrace();             }             try {                 ajsonstring1 = jobject.getstring("value");             } catch (jsonexception e) {                 // todo auto-generated catch block                 e.printstacktrace();             }             try {                 ajsonstring2 = jobject.getstring("timestamp");             } catch (jsonexception e) {                 // todo auto-generated catch block                 e.printstacktrace();             }               return ajsonstring1;          }              protected void onpostexecute(string result) {                 textview.settext(ajsonstring1);               }      }

can see problem here? have idea?

thanks in advance

edit: here logcat:

   04-25 16:27:06.851: w/system.err(4697):  @     android.os.asynctask$2.call(asynctask.java:287)    04-25 16:27:06.861: w/system.err(4697):  @ java.util.concurrent.futuretask.run(futuretask.java:234)    04-25 16:27:06.861: w/system.err(4697):  @ android.os.asynctask$serialexecutor$1.run(asynctask.java:230)    04-25 16:27:06.871: w/system.err(4697):  @ java.util.concurrent.threadpoolexecutor.runworker(threadpoolexecutor.java:1080)    04-25 16:27:06.871: w/system.err(4697):  @ java.util.concurrent.threadpoolexecutor$worker.run(threadpoolexecutor.java:573)    04-25 16:27:06.881: w/system.err(4697):  @ java.lang.thread.run(thread.java:856)    04-25 16:27:06.891: w/dalvikvm(4697): threadid=11: thread exiting uncaught exception (group=0x40a71930)    04-25 16:27:06.911: e/androidruntime(4697): fatal exception: asynctask #1    04-25 16:27:06.911: e/androidruntime(4697): java.lang.runtimeexception: error occured while executing doinbackground()    04-25 16:27:06.911: e/androidruntime(4697):  @ android.os.asynctask$3.done(asynctask.java:299)    04-25 16:27:06.911: e/androidruntime(4697):  @ java.util.concurrent.futuretask.finishcompletion(futuretask.java:352)    04-25 16:27:06.911: e/androidruntime(4697):  @ java.util.concurrent.futuretask.setexception(futuretask.java:219)    04-25 16:27:06.911: e/androidruntime(4697):  @ java.util.concurrent.futuretask.run(futuretask.java:239)    04-25 16:27:06.911: e/androidruntime(4697):  @ android.os.asynctask$serialexecutor$1.run(asynctask.java:230)    04-25 16:27:06.911: e/androidruntime(4697):  @ java.util.concurrent.threadpoolexecutor.runworker(threadpoolexecutor.java:1080)    04-25 16:27:06.911: e/androidruntime(4697):  @ java.util.concurrent.threadpoolexecutor$worker.run(threadpoolexecutor.java:573)    04-25 16:27:06.911: e/androidruntime(4697):  @ java.lang.thread.run(thread.java:856)    04-25 16:27:06.911: e/androidruntime(4697): caused by: java.lang.nullpointerexception    04-25 16:27:06.911: e/androidruntime(4697):  @ com.example.ayasms.mainactivity$readjson.doinbackground(mainactivity.java:189)    04-25 16:27:06.911: e/androidruntime(4697):  @ com.example.ayasms.mainactivity$readjson.doinbackground(mainactivity.java:1)    04-25 16:27:06.911: e/androidruntime(4697):  @ android.os.asynctask$2.call(asynctask.java:287)    04-25 16:27:06.911: e/androidruntime(4697):  @ java.util.concurrent.futuretask.run(futuretask.java:234)    04-25 16:27:06.911: e/androidruntime(4697):  ... 4 more

i assume try catch error handling inside asyncjob problem.

for example if line httpclient.execute(httppost);thrown exception catch , print stderr (which partly visible in logcat) continue!

of course without having executed httpclient.execute(..) have no response , therefore getting nullpointerexception.

conclusion: pack inside asyncjob in 1 try catch environment. furthermore should investigate class fails first , find out why.

try {     response = httpclient.execute(httppost);     httpentity entity = response.getentity();     inputstream = entity.getcontent();     reader = new bufferedreader(new inputstreamreader(inputstream, "utf-8"), 8);     stringbuilder sb = new stringbuilder();      string line = null;     while ((line = reader.readline()) != null) {     sb.append(line + "\n");     }     result = sb.tostring();     jobject = new jsonobject(result);       ajsonstring1 = jobject.getstring("value");     ajsonstring2 = jobject.getstring("timestamp");     return ajsonstring1; } catch (clientprotocolexception e) {     e.printstacktrace(); } catch (ioexception e) {     e.printstacktrace(); } catch (illegalstateexception e) {     e.printstacktrace(); } catch (unsupportedencodingexception e) {     e.printstacktrace();   } catch (jsonexception e) {     e.printstacktrace(); }            return null; // error case

Popular posts from this blog

How to calculate SNR of signals in MATLAB? -

-
i've encountered simple, yet fundamental problem on calculating snr: there several signals : s1 = original , pure clean signal without noise. n1 = white gaussian noise going added s1. s2 = s1 + n1 (the noisy signal before performing noise-reduction algorithm) s3 = noise-reduced signal (after performing noise reduction algorithm) n2 = s3 - s1 (the amount of noise after performing noise-reduction algorithm) now want compare snr before , after performing noise-reduction algorithm. which signals should consider snr_before!? s1/n1 or s2/n1 ? which signals should consider snr_after!? s3/n1 or s3/n2 ? which commands or functions should use in matlab in order compute snr_before , snr_after? thanks billion putting time on helping me. what know calculating snr before : snrbeforenoise = mean( signal .^ 2 ) / mean( noise .^ 2 ); and snr after : residual_noise = signal - noise_reduced_signal; snr_after = mean( signal .^ 2 ) / mean( residual_noise .^ 2
Read more

c# - Attempting to upload to FTP: System.Net.WebException: System error -

-
i have api takes in xml , uploads files based on information in xml. uploads on schedule (also xml), , have tested surrounding , know works. i getting error 40% of time on first file attempt upload in each time cycle (time cycle = 45 minutes files, 30 minutes others). here code upload: try { loggerftp.log("uploading file: " + filename, false); // create request. ftpwebrequest request = (ftpwebrequest)webrequest.create(appsettingsftp.ftpurl + @"/" + filename); request.method = webrequestmethods.ftp.uploadfile; request.timeout = 6000000; //set 100 minutes //request.timeout = -1; //set infinite // add login credentials. request.credentials = new networkcredential(appsettingsftp.ftplogin, appsettingsftp.ftppassword); // grab file contents. streamreader sourcestream = new streamreader(appsettingsftp.uploadfiledirectory + filename); byte[] filecontents = encoding.utf8.getbytes(sourcestream.readtoend()); sourcest
Read more

ios - UISlider customization: how to properly add shadow to custom knob image -

-
Image
i need place custom knob image shadow uislider. far have image of 38x38, of there region defines shadow of knob. now while using image, when slide knob extreme ends actual knob not able cover end points, hence end points visible under transparent region of knob image this code using customize uislider uiimage *slidebtimg = [uiimage imagenamed:sliderknobimg]; [self.ratingslider setthumbimage:slidebtimg forstate:uicontrolstatenormal]; [self.ratingslider setthumbimage:slidebtimg forstate:uicontrolstatehighlighted]; how can implement custom knob shadow beneath it, covering end points?? look inside uislider.h , there methods let customize slider knob , track needed. (ios 2.0 , above) // lets subclass lay out track , thumb needed - (cgrect)minimumvalueimagerectforbounds:(cgrect)bounds; - (cgrect)maximumvalueimagerectforbounds:(cgrect)bounds; - (cgrect)trackrectforbounds:(cgrect)bounds; - (cgrect)thumbrectforbounds:(cgrect)bounds trackrect:(cgrect)rect value:
Read more