Android ListView not poulating with json datas -
i want populate listview json values. i'm able json values, dont know problem is.
in logcat shows nullpointerexception , unfortunately activity stops.
suggesstion plz......
my java
public class certify_absent_list extends activity { private static listview listview; private static list<string> list; private string teachername,date; @override protected void oncreate(bundle savedinstancestate) { // todo auto-generated method stub super.oncreate(savedinstancestate); //setcontentview(r.layout.); listview=(listview) findviewbyid(r.id.listview1); list=new arraylist<string>(); teachername=getintent().getextras().getstring("teachername"); date=getintent().getextras().getstring("today"); new absent_list_bg_task().execute(); } private class absent_list_bg_task extends asynctask<string,void,string> { protected string doinbackground(string... params) { try{ string link="http://192.168.1.11:81/schoolapp/absent_list.php"; string data = urlencoder.encode("teachername", "utf-8") + "=" + urlencoder.encode("teacher1", "utf-8"); data += "&" + urlencoder.encode("date", "utf-8") + "=" + urlencoder.encode("2013-01-01", "utf-8"); /* string data = urlencoder.encode("teachername ", "utf-8") + "=" + urlencoder.encode("teacher1", "utf-8"); data += "&" + urlencoder.encode("date", "utf-8") + "=" + urlencoder.encode("2013-01-01", "utf-8");*/ url url = new url(link); urlconnection conn = url.openconnection(); conn.setdooutput(true); outputstreamwriter wr = new outputstreamwriter (conn.getoutputstream()); wr.write( data ); wr.flush(); bufferedreader reader = new bufferedreader (new inputstreamreader(conn.getinputstream())); stringbuilder sb = new stringbuilder(); string line = null; // read server response while((line = reader.readline()) != null) { sb.append(line); break; } return sb.tostring(); }catch(exception e){ return new string("exception: " + e.getmessage()); } } @override protected void onpostexecute(string result) { arrayadapter<string> adapter = null; jsonarray arr = null; jsonobject obj = null; toast.maketext(certify_absent_list.this,result, toast.length_long).show(); if(result.equals("wrong")) { toast.maketext(certify_absent_list.this,"invalid username or password.", toast.length_long).show(); } else { toast.maketext(certify_absent_list.this,result, toast.length_long).show(); try { arr=new jsonarray(result); } catch (jsonexception e) { // todo auto-generated catch block e.printstacktrace(); } for(int i=0;i<arr.length();i++) { try { obj=arr.getjsonobject(i); } catch (jsonexception e) { // todo auto-generated catch block e.printstacktrace(); } try { list.add(obj.getstring("childname")); } catch (jsonexception e) { // todo auto-generated catch block e.printstacktrace(); } toast.maketext(certify_absent_list.this,list.get(i).tostring(), toast.length_long).show(); } } adapter=new arrayadapter<string>(certify_absent_list.this, android.r.layout.simple_list_item_1, list); //adapter.notifydatasetchanged(); listview.setadapter(adapter); } } } json output
[{"childname":""},{"childname":"childname1"},{"childname":"childname7"},{"childname":"childname11"},{"childname":"childname11"},{"childname":"childname11"}] logcat:
03-21 07:35:29.128: e/androidruntime(1443): java.lang.nullpointerexception 03-21 07:35:29.128: e/androidruntime(1443): @ com.example.certify_teacher_login.certify_absent_list$absent_list_bg_task.onpostexecute(certify_absent_list.java:121) 03-21 07:35:29.128: e/androidruntime(1443): @ com.example.certify_teacher_login.certify_absent_list$absent_list_bg_task.onpostexecute(certify_absent_list.java:1) 03-21 07:35:29.128: e/androidruntime(1443): @ android.os.asynctask.finish(asynctask.java:632) 03-21 07:35:29.128: e/androidruntime(1443): @ android.os.asynctask.access$600(asynctask.java:177) 03-21 07:35:29.128: e/androidruntime(1443): @ android.os.asynctask$internalhandler.handlemessage(asynctask.java:645) 03-21 07:35:29.128: e/androidruntime(1443): @ android.os.handler.dispatchmessage(handler.java:102) 03-21 07:35:29.128: e/androidruntime(1443): @ android.os.looper.loop(looper.java:137) 03-21 07:35:29.128: e/androidruntime(1443): @ android.app.activitythread.main(activitythread.java:4998) 03-21 07:35:29.128: e/androidruntime(1443): @ java.lang.reflect.method.invokenative(native method) 03-21 07:35:29.128: e/androidruntime(1443): @ java.lang.reflect.method.invoke(method.java:515) 03-21 07:35:29.128: e/androidruntime(1443): @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:777) 03-21 07:35:29.128: e/androidruntime(1443): @ com.android.internal.os.zygoteinit.main(zygoteinit.java:593) 03-21 07:35:29.128: e/androidruntime(1443): @ dalvik.system.nativestart.main(native method)
//setcontentview(r.layout.); why line commented ? don't extend listactivity or use fragments either. unless thats typing mistake not going work !
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