Android : Image is not displaying when using image loader android

I am using image loader to display image and text from json parsing. text is displaying but image is not displaying. No error but it's displaying default icon. anyone please help me why image is not displaying. My code is as follows:

 public class GridAdapter extends ArrayAdapter<Persons> {
 ArrayList<Persons> personList;
 LayoutInflater layoutInflater;
 int Resource;
 ViewHolder viewHolder;
 ImageLoader imageLoader; // declared image laoder

 public GridAdapter(Context context, int resource, ArrayList<Persons> objects) {
    super(context, resource, objects);
    layoutInflater = (LayoutInflater) context
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    Resource = resource;
    personList = objects;
    }
   @Override
  public int getCount() {
  // TODO Auto-generated method stub
return super.getCount();
  }
 @Override
 public View getView(int position, View convertView, ViewGroup parent) {
View v= convertView;
 imageLoader = new ImageLoader(getContext()); // since thrown null pointer exception when i   declared this, it's not declaring null pointer exception but image is not displaying, default icon   set in ImageLoader is displaying..

if(v==null){
    viewHolder = new ViewHolder();
    v = layoutInflater.inflate(Resource, null);
    viewHolder.tvName=(TextView)v.findViewById(R.id.tvname);
    viewHolder.imageview=(ImageView)v.findViewById(R.id.picture);
    v.setTag(viewHolder);


}
else{
    viewHolder = (ViewHolder) v.getTag();

    }
   viewHolder.tvName.setText(personList.get(position).getName());
  imageLoader.DisplayImage(personList.get(position).getImage(),viewHolder.imageview);// this is not working..
// TODO Auto-generated method stub
  return v;
  }
static class ViewHolder {
public ImageView imageview;
public TextView tvName;


  }

}