java - setListAdapter() not working -

import android.app.activity; import android.os.bundle; import android.app.listactivity; import android.database.cursor; import android.net.uri; import android.provider.contactscontract; import android.widget.simplecursoradapter;  public class mainactivity extends activity {      @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);         uri allcontacts = uri.parse("content://contacts/people");             cursor c = managedquery(allcontacts, null, null, null, null);             string[] columns = new string[] {             contactscontract.contacts.display_name,             contactscontract.contacts._id};             int[] views = new int[] {r.id.contactname, r.id.contactid};             simplecursoradapter adapter =             new simplecursoradapter(this, r.layout.activity_main, c, columns,views);                 this.setlistadapter(adapter);     }  } 

it shows error :the method setlistadapter(simplecursoradapter) undefined type mainactivity

in order use setlistadapter class has extends listactivity not activity. change

public class mainactivity extends activity 

with

public class mainactivity extends listactivity