interact with custom list adapter on the activity which is embedded in

Question

I have a custom list adapter which is inflated in a fragment, and that fragment is embedded on an activity, i want to implement an interface to handle clicks on an image on that adapter from the activity class.. but im getting null pointer exception .. here are my codes:

this is part of my custom adapter class :

public ActionSelection mCallBack;
public interface ActionSelection {
    public void onActionSelected(int position);
}

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

    View view = convertView;

    LayoutInflater inflater = (LayoutInflater) getContext().
            getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    view = inflater.inflate(R.layout.main_list_item, null);

    // Obtain current mainListItem using position
    MainListItem item = mainListItems.get(position);

    // Set the custom view
    if (item != null) {

        ((SmartImageView) view.findViewById(R.id.imageview_mainlist_profile_picture)).
                setImageUrl(item.getProfile_picture());

        ((TextView) view.findViewById(R.id.textview_mainlist_fullname)).
                setText(item.getFullname());

        ((TextView) view.findViewById(R.id.textview_mainlist_username)).
                setText(item.getUsername());

        ((ImageView) view.findViewById(R.id.imageview_mainlist_action)).
                setImageResource(item.getAction());

        ImageView action = (ImageView) (view.findViewById(R.id.imageview_mainlist_action));
        action.setId(position);

        action.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mCallBack.onActionSelected(5);
            }
        });


    }

and on my MainActivity i implemented the interface with the following code:

@Override
public void onActionSelected(int position) {
    Log.v("test", String.valueOf(position));
}

Answer 1

You never set the mCallBack variable to anything. You could for example pass it in the constructor of your adapter.