NullPointer when dynamically creating TableLayout in Android -

i trying add table view in fragment getting nullpointer when try add row layout. tl.addview(tr_headings); looks causing crash.

thanks looking @ this!

 public class historyfragment extends fragment {  arraylist<workouts> workout_list; tablelayout tablelayout;  public historyfragment() {     // required empty public constructor }  @override public view oncreateview(layoutinflater inflater, viewgroup container,         bundle savedinstancestate) {       string name = "bench press";     string reps = "10";     string weight = "150";     string comment = "good weight. last rep tough";     simpledateformat  df = new simpledateformat("yyyy/mm/dd hh:mm");     date d = new date();     string date = df.format(d);     workout_list = new arraylist<workouts>();      for(int = 0; < 10; i++){          workouts workout = new workouts(name, reps, weight, comment, date);         workout_list.add(workout);     }      view rootview = inflater.inflate(r.layout.fragment_log, container, false);       tablelayout tl = (tablelayout) rootview.findviewbyid(r.id.historytable);      tablerow tr_headings = new tablerow(getactivity());      textview name_heading = new textview(getactivity());     textview reps_heading = new textview(getactivity());     textview weight_heading = new textview(getactivity());     textview date_heading = new textview(getactivity());     textview comment_heading = new textview(getactivity());      name_heading.settext("exercise name");     reps_heading.settext("reps");     weight_heading.settext("weight");     date_heading.settext("date");     comment_heading.settext("comment");      tr_headings.addview(name_heading);     tr_headings.addview(reps_heading);     tr_headings.addview(weight_heading);     tr_headings.addview(date_heading);     tr_headings.addview(comment_heading);      tl.addview(tr_headings); //null pointer here!      for(int j = 0; j < workout_list.size(); j++){          textview tv_name = new textview(getactivity());         textview tv_reps = new textview(getactivity());         textview tv_weight = new textview(getactivity());         textview tv_date = new textview(getactivity());         textview tv_comment = new textview(getactivity());          tv_name.settext(workout_list.get(j).getexercisename());         tv_reps.settext(workout_list.get(j).getnumreps());         tv_weight.settext(workout_list.get(j).getweight());         tv_date.settext(workout_list.get(j).getdate());         tv_comment.settext(workout_list.get(j).getcomment());          tablerow tr = new tablerow(getactivity());          tr.addview(tv_name);         tr.addview(tv_reps);         tr.addview(tv_weight);         tr.addview(tv_date);         tr.addview(tv_comment);          tl.addview(tr);      }      // inflate layout fragment     return rootview; }  }