java - Android: FATAL EXCEPTION: main -

i new android development. creating app shows list of addresses in list view. has 2 activities. dashboardgridactivity main activity(this activity shows icons in gridview). second displayactivity(this activity reads data xml , displays in list view)called in onitemclick function of dashboardgridactivity. following displayactivity.java file:

public class displayactivity extends activity {  listview listview; private string tag_name;  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     setcontentview(r.layout.activity_display);      listview = (listview) findviewbyid(r.id.list);      intent intent = getintent();     if(intent!= null)     {         //int imageid = intent.getintextra("dashboardimage",r.drawable.apartments);         tag_name = intent.getstringextra("dashitemname");     }      list<nameaddress> nameaddresslist = null;     try {         xmlpullparserhandler parser = new xmlpullparserhandler(tag_name);         nameaddresslist = parser.parse(getassets().open("data.xml"));         arrayadapter<nameaddress> adapter =             new arrayadapter<nameaddress>(this,r.layout.list_item, nameaddresslist);         listview.setadapter(adapter);     } catch (ioexception e) {         e.printstacktrace();     } }  @override public boolean oncreateoptionsmenu(menu menu) {     // inflate menu; adds items action bar if present.     getmenuinflater().inflate(r.menu.display, menu);     return true;   } } 

onitemclick functionn dashboardgridactivity.java file

@override public void onitemclick(adapterview<?> adapterview, view view, int i, long l) {     intent intent = new intent(this, displayactivity.class);     viewholder holder= (viewholder) view.gettag();     dashboarditems temp = (dashboarditems) holder.myitem.gettag();     //intent.putextra("dashboardimage",temp.imageid);     intent.putextra("dashitemname",temp.itemname);     startactivity(intent); } 

when trying run app, shows icons in gridview, when click on icon says "unfortunately app has stopped". gives following logcat

logcat:

    04-11 13:34:20.695: i/choreographer(1155): skipped 183 frames!  application may doing work on main thread. 04-11 13:34:23.085: w/inputeventreceiver(1155): attempted finish input event input event receiver has been disposed. 04-11 13:34:29.995: d/androidruntime(1155): shutting down vm 04-11 13:34:29.995: w/dalvikvm(1155): threadid=1: thread exiting uncaught exception (group=0xb2a2dba8) 04-11 13:34:30.075: e/androidruntime(1155): fatal exception: main 04-11 13:34:30.075: e/androidruntime(1155): process: com.asm.offcampusresources, pid: 1155 04-11 13:34:30.075: e/androidruntime(1155): java.lang.nullpointerexception 04-11 13:34:30.075: e/androidruntime(1155):     @ com.asm.offcampusresources.dashboardgridactivity.onitemclick(dashboardgridactivity.java:55) 04-11 13:34:30.075: e/androidruntime(1155):     @ android.widget.adapterview.performitemclick(adapterview.java:299) 04-11 13:34:30.075: e/androidruntime(1155):     @ android.widget.abslistview.performitemclick(abslistview.java:1113) 04-11 13:34:30.075: e/androidruntime(1155):     @ android.widget.abslistview$performclick.run(abslistview.java:2904) 04-11 13:34:30.075: e/androidruntime(1155):     @ android.widget.abslistview$3.run(abslistview.java:3638) 04-11 13:34:30.075: e/androidruntime(1155):     @ android.os.handler.handlecallback(handler.java:733) 04-11 13:34:30.075: e/androidruntime(1155):     @ android.os.handler.dispatchmessage(handler.java:95) 04-11 13:34:30.075: e/androidruntime(1155):     @ android.os.looper.loop(looper.java:136) 04-11 13:34:30.075: e/androidruntime(1155):     @ android.app.activitythread.main(activitythread.java:5017) 04-11 13:34:30.075: e/androidruntime(1155):     @ java.lang.reflect.method.invokenative(native method) 04-11 13:34:30.075: e/androidruntime(1155):     @ java.lang.reflect.method.invoke(method.java:515) 04-11 13:34:30.075: e/androidruntime(1155):     @ com.android.internal.os.zygoteinit$methodandargscaller.run(zygoteinit.java:779) 04-11 13:34:30.075: e/androidruntime(1155):     @ com.android.internal.os.zygoteinit.main(zygoteinit.java:595) 04-11 13:34:30.075: e/androidruntime(1155):     @ dalvik.system.nativestart.main(native method) 04-11 13:34:33.635: i/process(1155): sending signal. pid: 1155 sig: 9 

please suggest me way resolve problem.

use code onitemclicklistener

@override     public void onitemclick(adapterview<?> adapterview, view view, int i, long l) {         intent intent = new intent(this, displayactivity.class);          dashboarditems temp = (dashboarditems) adapterview.getitematposition(i);         //intent.putextra("dashboardimage",temp.imageid);         intent.putextra("dashitemname",temp.itemname);         startactivity(intent);     }