java - JSON null Object Reference Error {Android} -
i have made application tutorial http://javatechig.com/android/json-feed-reader-in-android
but when run app in android studio there following errors
caused by: java.lang.nullpointerexception: attempt invoke virtual method 'int java.lang.string.length()' on null object reference @ org.json.jsontokener.nextcleaninternal(jsontokener.java:116) @ org.json.jsontokener.nextvalue(jsontokener.java:94) @ org.json.jsonobject.<init>(jsonobject.java:156) @ org.json.jsonobject.<init>(jsonobject.java:173) @ com.example.administrator.myapplication5.feedlistactivity.getjsonfromurl(feedlistactivity.java:127) @ com.example.administrator.myapplication5.feedlistactivity$downloadfilestask.doinbackground(feedlistactivity.java:85) @ com.example.administrator.myapplication5.feedlistactivity$downloadfilestask.doinbackground(feedlistactivity.java:67) @ android.os.asynctask$2.call(asynctask.java:288) @ java.util.concurrent.futuretask.run(futuretask.java:237) at android.os.asynctask$serialexecutor$1.run(asynctask.java:231) at java.util.concurrent.threadpoolexecutor.runworker(threadpoolexecutor.java:1112) at java.util.concurrent.threadpoolexecutor$worker.run(threadpoolexecutor.java:587) at java.lang.thread.run(thread.java:818) this feedlistactivity class
public class feedlistactivity extends activity { private arraylist<feeditem> feedlist = null; private progressbar progressbar = null; private listview feedlistview = null; @override public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_posts_list); progressbar = (progressbar) findviewbyid(r.id.progressbar); string url = "http://javatechig.com/api/get_category_posts/?dev=1&slug=android"; new downloadfilestask().execute(url); } public void updatelist() { feedlistview= (listview) findviewbyid(r.id.custom_list); feedlistview.setvisibility(view.visible); progressbar.setvisibility(view.gone); feedlistview.setadapter(new customlistadapter(this, feedlist)); feedlistview.setonitemclicklistener(new onitemclicklistener() { @override public void onitemclick(adapterview<?> a, view v, int position, long id) { object o = feedlistview.getitematposition(position); feeditem newsdata = (feeditem) o; intent intent = new intent(feedlistactivity.this, feeddetailsactivity.class); intent.putextra("feed", newsdata); startactivity(intent); } }); } private class downloadfilestask extends asynctask<string, integer, void> { @override protected void onprogressupdate(integer... values) { } @override protected void onpostexecute(void result) { if (null != feedlist) { updatelist(); } } @override protected void doinbackground(string... params) { string url = params[0]; // getting json string url jsonobject json = getjsonfromurl(url); //parsing json data parsejson(json); return null; } } public jsonobject getjsonfromurl(string url) { inputstream = null; jsonobject jobj = null; string json = null; // making http request try { // defaulthttpclient defaulthttpclient httpclient = new defaulthttpclient(); httppost httppost = new httppost(url); httpresponse httpresponse = httpclient.execute(httppost); httpentity httpentity = httpresponse.getentity(); = httpentity.getcontent(); bufferedreader reader = new bufferedreader(new inputstreamreader( is, "iso-8859-1"), 8); stringbuilder sb = new stringbuilder(); string line = null; while ((line = reader.readline()) != null) { sb.append(line + "\n"); } is.close(); json = sb.tostring(); } catch (unsupportedencodingexception e) { e.printstacktrace(); } catch (clientprotocolexception e) { e.printstacktrace(); } catch (ioexception e) { e.printstacktrace(); } try { jobj = new jsonobject(json); } catch (jsonexception e) { log.e("json parser", "error parsing data " + e.tostring()); } // return json string return jobj; } public void parsejson(jsonobject json) { try { // parsing json object if (json.getstring("status").equalsignorecase("ok")) { jsonarray posts = json.getjsonarray("posts"); feedlist = new arraylist<feeditem>(); (int = 0; < posts.length(); i++) { jsonobject post = (jsonobject) posts.getjsonobject(i); feeditem item = new feeditem(); item.settitle(post.getstring("title")); item.setdate(post.getstring("date")); item.setid(post.getstring("id")); item.seturl(post.getstring("url")); item.setcontent(post.getstring("content")); jsonarray attachments = post.getjsonarray("attachments"); if (null != attachments && attachments.length() > 0) { jsonobject attachment = attachments.getjsonobject(0); if (attachment != null) item.setattachmenturl(attachment.getstring("url")); } feedlist.add(item); } } } catch (jsonexception e) { e.printstacktrace(); } } } also, found answer (android strange error) didn't work
i thankful consider error , me solve that.
the exception thrown here:
try { jobj = new jsonobject(json); } catch (jsonexception e) { log.e("json parser", "error parsing data " + e.tostring()); } json null, , jsonobject can't created. please check why json not assigned , remains null in code:
string json = null; // making http request try { // defaulthttpclient defaulthttpclient httpclient = new defaulthttpclient(); httppost httppost = new httppost(url); httpresponse httpresponse = httpclient.execute(httppost); httpentity httpentity = httpresponse.getentity(); = httpentity.getcontent(); bufferedreader reader = new bufferedreader(new inputstreamreader( is, "iso-8859-1"), 8); stringbuilder sb = new stringbuilder(); string line = null; while ((line = reader.readline()) != null) { sb.append(line + "\n"); } is.close(); json = sb.tostring(); } catch (unsupportedencodingexception e) { e.printstacktrace(); } catch (clientprotocolexception e) { e.printstacktrace(); } catch (ioexception e) { e.printstacktrace(); } 
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