CodeLearn Twitter Tutorial nullpointer error on TweetAdapter.java

Question

I'm currently doing the Codelearn Twitter tutorial but I'm getting a null pointer in my code below - can someone please help me?

public class TweetAdapter extends ArrayAdapter<Tweet> {

private LayoutInflater inflater;
private ArrayList<Tweet> tweetsList;

 public TweetAdapter(Activity activity, List<Tweet> tweets) {
     super(activity, R.layout.row_tweet, tweets);
     tweetsList = (ArrayList<Tweet>) tweets;
     inflater = activity.getWindow().getLayoutInflater();
}

@Override
 public View getView(int position, View convertView, ViewGroup parent){

    Tweet t = tweetsList.get(position);

    ***TextView title = (TextView) convertView.findViewById(R.id.tweetTitle);***
    TextView body = (TextView) convertView.findViewById(R.id.tweetBody);

    title.setText(t.getTitle());
    body.setText(t.getBody());

    return inflater.inflate(R.layout.row_tweet, parent, false);
    }

}

Where are you getting the `NullPointerException`? Where the stars are? — Ross Drew, Aug 01 '14 at 11:57
On the Line TextView title = (TextView) convertView.findViewById(R.id.tweetTitle); — Barry the Beginner, Aug 01 '14 at 13:53
Just to be sure, can you also put your XML file so that it can be confirmed there is a field with id tweetTitle. Also, any link to the tutorial where instruction can be checked ? — Pocha, Aug 01 '14 at 14:02

score 1 · Accepted Answer · answered Aug 01 '14 at 12:00

Your convertView can be null. There is no guarantee that it will be non null. If there is no old view to reuse it will be null

Change

public View getView(int position, View convertView, ViewGroup parent)
{

Tweet t = tweetsList.get(position);

***TextView title = (TextView) convertView.findViewById(R.id.tweetTitle);***
TextView body = (TextView) convertView.findViewById(R.id.tweetBody);

title.setText(t.getTitle());
body.setText(t.getBody());

return inflater.inflate(R.layout.row_tweet, parent, false);
}

to

public View getView(int position, View convertView, ViewGroup parent)
{
  if(convertView==null)
    convertView = inflater.inflate(R.layout.row_tweet, parent, false);

  Tweet t = tweetsList.get(position);

  ***TextView title = (TextView) convertView.findViewById(R.id.tweetTitle);***
  TextView body = (TextView) convertView.findViewById(R.id.tweetBody);

  title.setText(t.getTitle());
  body.setText(t.getBody());

  return convertView;
}

You have to check whether convertView is non null or not and if it is null you need to inflate your layout in it.

You should also take a look at ViewHolder pattern

Thanks Apoorv - I'll give that a whirl – Barry the Beginner Aug 01 '14 at 13:54 — Barry the Beginner, Aug 01 '14 at 13:54

CodeLearn Twitter Tutorial nullpointer error on TweetAdapter.java

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