android - null pointer exception for custonlistadapter? -

public class listpage extends listactivity {     thelists a[] = new thelists[1];     protected void oncreate(bundle savedinstancestate)     {         super.oncreate(savedinstancestate);         requestwindowfeature(window.feature_no_title);         setcontentview(r.layout.list_page);          setlistadapter(new myadapter());     }      @override     protected void onlistitemclick(listview l, view v, int position, long id)     {          class myadapter extends arrayadapter<thelists>         {             myadapter()             {                 super(listpage.this, r.layout.list_row, r.id.sname, a);             }              @override             public view getview(int position, view convertview, viewgroup parent)             {                 layoutinflater inflater = getlayoutinflater();                 view row = inflater.inflate(r.layout.list_row,parent,false);                  textview name,category,id;                  name=(textview)row.findviewbyid(r.id.sname);                 category=(textview)row.findviewbyid(r.id.scategory);                 id=(textview)row.findviewbyid(r.id.sid);                 name.settext(a[0].schemelist[position]);                 category.settext(a[0].categorylist[position]);                 id.settext(a[0].idlist[position]);                 return(row);             }         }     } } 

i'm getting runtime error says

05-02 18:56:32.224: e/androidruntime(775): fatal exception: main 05-02 18:56:32.224: e/androidruntime(775): java.lang.nullpointerexception 05-02 18:56:32.224: e/androidruntime(775):  @ com.example.listinflator_demo.listpage$myadapter.getview(listpage.java:75) 05-02 18:56:32.224: e/androidruntime(775):  @ android.widget.abslistview.obtainview(abslistview.java:2159) 

what changes needed ?

in constructor, there strange :

you pass parameter super. isn't initialized, never. value ?

anyhow, suggest understand better want null pointer exception means. meet kind of error quite when programming in java, better understanding how find , correct them yourself, it's more interesting getting question answered.