android - NullPointerException when setAdapter ListView in onPostExcute -


i create listview , set action loadmore when scrolling final item. listview works until scroll final item, action loadmore listview running. got error:

07-01 22:48:10.792: e/androidruntime(4691): java.lang.nullpointerexception 07-01 22:48:10.792: e/androidruntime(4691):     @ android.widget.listview.clearrecycledstate(listview.java:516) 07-01 22:48:10.792: e/androidruntime(4691):     @ android.widget.listview.resetlist(listview.java:503) 07-01 22:48:10.792: e/androidruntime(4691):     @ android.widget.listview.setadapter(listview.java:445) 07-01 22:48:10.792: e/androidruntime(4691):     @ com.example.mainactivity$1processdatatask.onpostexecute(mainactivity.java:192) 07-01 22:48:10.792: e/androidruntime(4691):     @ com.example.mainactivity$1processdatatask.onpostexecute(mainactivity.java:1) 07-01 22:48:10.792: e/androidruntime(4691):     @ android.os.asynctask.finish(asynctask.java:631) 07-01 22:48:10.792: e/androidruntime(4691):     @ android.os.asynctask.access$600(asynctask.java:177) 07-01 22:48:10.792: e/androidruntime(4691):     @ android.os.asynctask$internalhandler.handlemessage(asynctask.java:644) 07-01 22:48:10.792: e/androidruntime(4691):     @ android.os.handler.dispatchmessage(handler.java:99) 07-01 22:48:10.792: e/androidruntime(4691):     @ android.os.looper.loop(looper.java:137) 07-01 22:48:10.792: e/androidruntime(4691):     @ android.app.activitythread.main(activitythread.java:5103) 07-01 22:48:10.792: e/androidruntime(4691):     @ java.lang.reflect.method.invokenative(native method) 07-01 22:48:10.792: e/androidruntime(4691):     @ java.lang.reflect.method.invoke(method.java:525) 07-01 22:48:10.792: e/androidruntime(4691):     @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:737) 07-01 22:48:10.792: e/androidruntime(4691):     @ com.android.internal.os.zygoteinit.main(zygoteinit.java:553) 07-01 22:48:10.792: e/androidruntime(4691):     @ dalvik.system.nativestart.main(native method)

nullpointexception got in listview.setadapter(adapter); in onpostexcute method, in asynctask.

this class:

public class mainactivity extends actionbaractivity {      list<person> listdata;     listview listview;     customadapter adapter;      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.person_layout);          listview = (listview) findviewbyid(r.id.list_view_person);         listview.setdivider(null);         listdata = new arraylist<person>();          processdata();          listview.setonscrolllistener(new onscrolllistener() {             @override             public void onscrollstatechanged(abslistview view, int scrollstate) {              }             @override             public void onscroll(abslistview view, int firstvisibleitem, int visibleitemcount,                     int totalitemcount) {                 if(totalitemcount > 0 && firstvisibleitem + visibleitemcount == totalitemcount) {                     processdata();                 }             }         });     }      public void processdata(){         class processdatatask extends asynctask<void, void, string> {              public processdatatask() {                 super();              }              @override                 protected string doinbackground(void... params) {                     .........//add data listdata here                         return null;                 }              @override                 protected void onpostexecute(string result) {                       if(listdata.size() > 0){                          adapter = new customadapter(listdata, mainactivity.this);                          if(listview != null && adapter != null)                             listview.setadapter(adapter);                      }                      super.onpostexecute(result);                 }         }         processdatatask processdata = new processdatatask();         processdata.execute();     }  }

is there suggestion solve error?

you forget arraylist initialization... add code 

listdata = new arraylist<person>(); processdata();

-

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