checkbox - How to sum checkboxes value in android? -

i have problem in java.

package apa.y;  import android.app.activity; import android.os.bundle; import android.view.view; import android.widget.checkbox; import android.widget.textview;    public class myprice extends activity  {     /** called when activity first created. */       checkbox book,pencil;     textview total;     int sum=0;      public void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);      setcontentview(r.layout.mymain);     pencil = (checkbox) findviewbyid(r.id.pencil);     book = (checkbox) findviewbyid(r.id.book);     total = (textview) findviewbyid(r.id.total);      }      public void onclick(view v) {          sum = 0;         if (pencil.ischecked()) {sum += 10;}else{sum +=0;}         if (book.ischecked())   {sum += 5;}else{sum +=0;}          total.settext("total: "+sum);      } } 

if book , pencil checkbox , 1 textview, how sum it? existing code didn't work.

what clicking on? checkboxes? need kind of listener views. 2 options provided here: android: checkbox listener

if want use onclick method have now, change this:

public class myprice extends activity implements onclicklistener  { 

and make sure set onclicklistener both checkboxes:

pencil = (checkbox) findviewbyid(r.id.pencil); pencil.setonclicklistener(this); book = (checkbox) findviewbyid(r.id.book); book.setonclicklistener(this);