java - TextView giving NulllPointerException in AsyncTask -

that should trivial , wondering whats happening, copied code online course, worked , , giving me nullpointer exception.everything seems right far

here mainactivity class

public class mainactivity extends activity {   button button1; textview textview2; progressbar progressbar; @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);       setcontentview(r.layout.activity_main);      textview textview2=(textview)findviewbyid(r.id.textview2);      button button1=(button)findviewbyid(r.id.button1);        progressbar progressbar1=(progressbar)findviewbyid(r.id.progressbar1);          button1.setonclicklistener(new button.onclicklistener() {             public void onclick(view v) {                asy task=new asy(mainactivity.this);             task.execute("process me","process me too");                  }           }); } 

}

then thats sniplet async

public class asy extends asynctask<string,integer,long> {   public mainactivity host;  public asy (mainactivity host) {     this.host=host;  } @override protected void onpreexecute() {     // todo auto-generated method stub        super.onpreexecute();   host.textview2.settext("processing..");  ; } 

and in logcat see

e/androidruntime(28044): fatal exception: main e/androidruntime(28044): java.lang.nullpointerexception e/androidruntime(28044):    @ com.example.async.asy.onpreexecute(asy.java:25) e/androidruntime(28044):    @ android.os.asynctask.execute(asynctask.java:391) 

i mean looks right me , initialize textview after setcontentview, use constructors, why not initialized in asynctask ?

declare textview instance global , use in asynctask.

like..

textview textview2;     @override     protected void oncreate(bundle savedinstancestate) {         super.oncreate(savedinstancestate);           setcontentview(r.layout.activity_main);          textview2=(textview)findviewbyid(r.id.textview2); 

and use :

textview2.settext("processing..");