java - Android Attempt to read on a null object reference -


i looking create list json content. here adapter code :

public class answersadapter extends arrayadapter<answer> {      static context context;     static int layoutresourceid;     answer data[] = null;      public answersadapter(context context, int layoutresourceid, answer[] data) {         super(context, layoutresourceid, data);         this.layoutresourceid = layoutresourceid;         this.context = context;         this.data = data;     }      public long getitemid(int position) {         return position;     }      public view getview(int position, view convertview, viewgroup parent) {         view row = convertview;         answerholder holder = null;         if(row == null)         {             layoutinflater inflater = ((activity)context).getlayoutinflater();             row = inflater.inflate(layoutresourceid, parent, false);             holder = new answerholder();             holder.txttitle = (textview)row.findviewbyid(r.id.answertext);             holder.txttitle2 = (textview)row.findviewbyid(r.id.answerauthor);             holder.txttitle3 = (textview)row.findviewbyid(r.id.answervotes);             row.settag(holder);         }         else         {             holder = (answerholder)row.gettag();         }         answer hold = data[position];             holder.txttitle.settext(html.fromhtml(hold.text));             holder.txttitle2.settext(hold.author);             holder.txttitle3.settext(hold.votes);          return row;     }      static class answerholder     {         textview txttitle;         textview txttitle2;         textview txttitle3;     } }

and facing error :

java.lang.nullpointerexception: attempt read field 'java.lang.string com.example.shivam.stackoverflow.answer.text' on null object reference

on line 

holder.txttitle.settext(html.fromhtml(hold.text));

your data array has null values. immediate cause of npe, because hold ends null positions. avoid npe if test that, (as point out in comment) adapter won't behave quite properly. cannot ignore rows have null data values.

as aside, should eliminate data member field. array reference being kept arrayadapter superclass. use getitem(position) whenever have used data[position]. while won't address npe problem, simplify things bit, seen below.

you have several options:

  1. find out why entries of data null begin , eliminate root problem. however, may normal (outside context of adapter) data have null entries.
  2. revise getview method set views in holder specific values indicate "data missing"—perhaps blank, perhaps "no data" message. (in other words, don't skip processing. causing combination of blank , duplicate rows.)

  3. revise constructor eliminate null entries data. result in shorter list. code accomplish might be:

    public answersadapter(context context, int layoutresourceid, answer[] data) {     super(context, layoutresourceid, trimmeddata(data));     this.layoutresourceid = layoutresourceid;     this.context = context; }  /**  * copy data new array has no nulls.  */ private static answer[] trimmeddata(answer[] data) {     answer[] result = new answer[data.length];     int n = 0;     (answer : data) {         if (a != null) {             result[n++] = a;         }     }     if (n < data.length) {         result = arrays.copyof(result, n, answer.class);     }     return result; }

    however, might cause problems elsewhere in code if need maintain correspondence between listview position , original data array.

another aside: can eliminate getitemid() method; default implementation in arrayadapterdoes same thing.


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