How to add viewholder to this getView?

Question

I'm new to coding. While executing, I get an error related to nullpointerException

public class DrawerItemCustomAdapter extends ArrayAdapter<DataModel> {

    Context mContext;
    int layoutResourceId;
    DataModel data[] = null;

    public DrawerItemCustomAdapter(Context mContext, int layoutResourceId, DataModel[] data) {

        super(mContext, layoutResourceId, data);
        this.layoutResourceId = layoutResourceId;
        this.mContext = mContext;
        this.data = data;
    }

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

        View listItem = convertView;

        if (convertView == null) {

            LayoutInflater inflater = ((Activity) mContext).getLayoutInflater();
            listItem = inflater.inflate(layoutResourceId, parent, false);

            ImageView imageViewIcon = (ImageView) listItem.findViewById(R.id.imageViewIcon);
            TextView textViewName = (TextView) listItem.findViewById(R.id.textViewName);

            DataModel folder = data[position];


            imageViewIcon.setImageResource(folder.icon);
            textViewName.setText(folder.name);


        }
        return listItem;
    }
}

This is the logcat

java.lang.NullPointerException
   at com.example.sandeku7.roadwage.DrawerItemCustomAdapter.getView(DrawerItemCustomAdapter.java:43)
   at android.widget.AbsListView.obtainView(AbsListView.java:2257)
   at android.widget.ListView.makeAndAddView(ListView.java:1790)
   at android.widget.ListView.fillDown(ListView.java:691)
   at android.widget.ListView.fillFromTop(ListView.java:752)
   at android.widget.ListView.layoutChildren(ListView.java:1630)
   at android.widget.AbsListView.onLayout(AbsListView.java:2089)
   at android.view.View.layout(View.java:14828)
   at android.view.ViewGroup.layout(ViewGroup.java:4631)
   at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:1211)
   at android.view.View.layout(View.java:14828)
   at android.view.ViewGroup.layout(ViewGroup.java:4631)
   at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
   at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
   at android.view.View.layout(View.java:14828)
   at android.view.ViewGroup.layout(ViewGroup.java:4631)
   at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)
   at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525)
   at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
   at android.view.View.layout(View.java:14828)
   at android.view.ViewGroup.layout(ViewGroup.java:4631)
   at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
   at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
   at android.view.View.layout(View.java:14828)
   at android.view.ViewGroup.layout(ViewGroup.java:4631)
   at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)
   at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525)
   at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
   at android.view.View.layout(View.java:14828)
   at android.view.ViewGroup.layout(ViewGroup.java:4631)
   at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
   at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
   at android.view.View.layout(View.java:14828)
   at android.view.ViewGroup.layout(ViewGroup.java:4631)
   at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2026)
   at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1783)
   at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1039)
   at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5648)
   at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
   at android.view.Choreographer.doCallbacks(Choreographer.java:574)
   at android.view.Choreographer.doFrame(Choreographer.java:544)
   at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
   at android.os.Handler.handleCallback(Handler.java:733)
   at android.os.Handler.dispatchMessage(Handler.java:95)
   at android.os.Looper.loop(Looper.java:136)
   at android.app.ActivityThread.main(ActivityThread.java:5052)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:515)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
   at dalvik.system.NativeStart.main(Native Method)

thanks for your help

http://stackoverflow.com/questions/3832254/how-can-i-make-my-arrayadapter-follow-the-viewholder-pattern — Charuක, Aug 04 '16 at 11:18
`folder` is entirely possible to be null. And a View holder won't solve the problem — OneCricketeer, Aug 04 '16 at 13:39

Sahana Prabhakar · Answer 1 · 2016-08-04T11:30:29.317

Modify your getView() method,

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

View listItem = convertView;

ViewHolder viewHolder =  null;
LayoutInflater inflater = (LayoutInflater) mContext
            .getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
if (convertView == null) {
    viewHolder = new viewHolder();
    convertView = inflater.inflate(layoutResourceId, parent, false);
    viewHolder.imageViewIcon = (ImageView) convertView.findViewById(R.id.imageViewIcon);
    viewHolder.textViewName = (TextView) convertView.findViewById(R.id.textViewName);
    convertView.setTag(viewHolder);
}else{
 viewholder = (ViewHolder)convertView.getTag();
}

    DataModel folder = data[position];

    viewHolder.imageViewIcon.setImageResource(folder.icon);
    viewHolder.textViewName.setText(folder.name);

return convertView;
}

inside the adapter create a ViewHolderClass example,

class ViewHolder{
 TextView textViewName;
 ImageView imageViewIcon;

}

thanks for your response , but the runtime exception thrown is still the same — MatrixMama, Aug 04 '16 at 12:28
Can you tell me on which line is the exception being thrown? — Sahana Prabhakar, Aug 04 '16 at 12:40

How to add viewholder to this getView?

1 Answers1