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Android Android Lists and Adapters (2015) Lists with RecyclerViews Using a Layout Manager

Null Pointer Exception.. App crashes on clicking Hourly Button.

The App Stormy crashes on clicking the Hourly Button. This question is followed by the answer for this problem. The error lies in HourAdapter class where we set mIconImageView.

public class HourAdapter extends RecyclerView.Adapter<HourAdapter.HourViewHolder>{

    private Hour[] mHours;

    public HourAdapter(Hour[] hours){
        mHours = hours;
    }

    @Override
    public HourViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        View view = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.hourly_list_item, parent, false);
        HourViewHolder viewHolder = new HourViewHolder(view);
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(HourViewHolder holder, int position) {

        holder.bindHour(mHours[position]);

    }

    @Override
    public int getItemCount() {
        return mHours.length;
    }

    public class HourViewHolder extends RecyclerView.ViewHolder {

        public TextView mTimeLabel,mSummarylabel,mTemperatureLabel;
        public ImageView mIconImageView;

        public HourViewHolder(View itemView) {
            super(itemView);

            mTimeLabel = (TextView) itemView.findViewById(R.id.timeHourLabel);
            mTemperatureLabel = (TextView) itemView.findViewById(R.id.temperatureHourLabel);
            mSummarylabel = (TextView) itemView.findViewById(R.id.summaryHourLabel);
            mIconImageView = (ImageView) itemView.findViewById(R.id.iconHourImageView);

        }

        public void bindHour(Hour hour){
               mTimeLabel.setText(hour.getHour());
               mTemperatureLabel.setText(hour.getTemperature() + ""); 
               mSummarylabel.setText(hour.getSummary());
               mIconImageView.setImageResource(hour.getIconId()); 
        }
    }
}

2 Answers

The error is caused at mIconImageView.setImageResource which is throwing a Null pointer exception.

The error arises because mIcon is set to null. In the Main Activity, when calling getHourlyForecastActivity, you should set

hour.setIcon(jsonHour.getString("Hour");

which i think many forgot to do because of which mIcon is set to default null and setImageResource is trying to throw an NullPointerException. If you have called setIcon on hour it should work fine.

Seth Kroger
Seth Kroger
56,413 Points

The problem with both solutions is that they are only covering over the problem instead of fixing it. Why is mIconImageView null and is that reason something you can fix?

You forgot a close ) in it should look like this

hour.setIcon(jsonHour.getString("Hour"));

But when you run this your whole app crashes it should be

hour.setIcon(jsonHour.getString("icon"));

Seth Kroger The error arises because mIcon is set to null. In the Main Activity, you should set

hour.setIcon(jsonHour.getString("Hour");

which i think many forgot to do because of which mIcon is set to default null and setImageResource is trying to throw an NullPointerException. If you have called setIcon on hour it should work fine. I'll update the answer soon.