Android ExpandableListView -

recently i'm trying use android's expandable list view, googled around , stumbled upon this

http://about-android.blogspot.com/2010/04/steps-to-implement-expandablelistview.html

i followed steps exactly, created file contain implementation of own adapter. on oncreate method of main activity call:

mentries = findviewbyid(r.id.entries);     expandablelistadapter adapter = new myexpandablelistadapter(this); mentries.setadapter(adapter); 

here's code (taken above url , modified):

import android.content.context; import android.view.gravity; import android.view.view; import android.view.viewgroup; import android.widget.abslistview; import android.widget.baseexpandablelistadapter; import android.widget.textview;  public class myexpandablelistadapter extends baseexpandablelistadapter {     private string[] groups = {"vehicle", "baj"};     private string[][] children = {         {"mol", "mor"},         {"in", "ruh"}     };      private context cxt;      public myexpandablelistadapter(context cxt) {         this.cxt = cxt;     }      @override     public object getchild(int grouppos, int childpos) {         return children[grouppos][childpos];     }      @override     public long getchildid(int grouppos, int childpos) {         return childpos;     }      @override     public view getchildview(int grouppos, int childpos,             boolean islastchild, view convertview, viewgroup parent) {         textview tv = getgenericview();         tv.settext(getchild(grouppos, childpos).tostring());         return tv;     }      @override     public int getchildrencount(int grouppos) {         return children[grouppos].length;     }      @override     public object getgroup(int grouppos) {         return groups[grouppos];     }      @override     public int getgroupcount() {         return groups.length;     }      @override     public long getgroupid(int grouppos) {         return grouppos;     }      public textview getgenericview() {         // layout parameters expandablelistview         abslistview.layoutparams lp = new abslistview.layoutparams(             viewgroup.layoutparams.fill_parent, 64);          textview tv = new textview(this.cxt); tv.setlayoutparams(lp);          // center text vertically         tv.setgravity(gravity.center_vertical | gravity.left);         // set text starting position         tv.setpadding(36, 0, 0, 0);         return tv;     }      @override     public view getgroupview(int grouppos, boolean isexpanded, view convertview,             viewgroup parent) {         textview tv = getgenericview();         tv.settext(getgroup(grouppos).tostring());         return null;     }      @override     public boolean hasstableids() {         return true;     }      @override     public boolean ischildselectable(int grouppos, int childpos) {         return true;     }  } 

the logcat spit these:

12-01 22:24:54.883: error/androidruntime(14424): java.lang.nullpointerexception 12-01 22:24:54.883: error/androidruntime(14424):     @ android.widget.abslistview.obtainview(abslistview.java:1276) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.widget.listview.makeandaddview(listview.java:1668) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.widget.listview.filldown(listview.java:637) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.widget.listview.fillfromtop(listview.java:694) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.widget.listview.layoutchildren(listview.java:1521) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.widget.abslistview.onlayout(abslistview.java:1113) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.view.view.layout(view.java:6830) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.widget.relativelayout.onlayout(relativelayout.java:900) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.view.view.layout(view.java:6830) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.widget.framelayout.onlayout(framelayout.java:333) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.view.view.layout(view.java:6830) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.widget.linearlayout.setchildframe(linearlayout.java:1119) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.widget.linearlayout.layoutvertical(linearlayout.java:998) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.widget.linearlayout.onlayout(linearlayout.java:918) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.view.view.layout(view.java:6830) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.widget.framelayout.onlayout(framelayout.java:333) 12-01 22:24:54.883: error/androidruntime(14424):     @ android.view.view.layout(view.java:6830) snip... 

anyone care shed light on this? =/

edit: i've implemented methods required in base class.

edit2: code added

finally got it... it's at:

    @override public view getgroupview(int grouppos, boolean isexpanded, view convertview,         viewgroup parent) {     textview tv = getgenericview();     tv.settext(getgroup(grouppos).tostring());     return null; } 

it's returning null... shouldn't code when i'm sleepy =/