LayoutInflater中的空指针异常

Question

我在LayoutInflator中遇到NullPointerException。我想做导航滑块菜单，但我有一个错误。你能救我吗？

public class CategoryAdapter extends BaseAdapter {

    private FragmentActivity nav_slider_activity;
    private LayoutInflater nav_slider_inflater;
    private List<Movie> nav_slider_movieitems;

    public CategoryAdapter(FragmentActivity nav_slider_activity, List<Movie> items){
        this.nav_slider_activity = nav_slider_activity;
        this.nav_slider_movieitems = items;
    }

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return nav_slider_movieitems.size();
    }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return nav_slider_movieitems.get(position);
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub
        if (nav_slider_inflater == null)
            nav_slider_inflater = (LayoutInflater) nav_slider_activity
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        if(convertView==null)
        convertView = nav_slider_inflater.inflate(R.layout.navigation_slider_list_layout, parent, false);

        if (nav_slider_imageLoader == null)
            nav_slider_imageLoader= AppData.getInstance().getImageLoader();
        NetworkImageView image = (NetworkImageView) convertView
                .findViewById(R.id.nav_slider_view);
        TextView nav_slider_title = (TextView) convertView.findViewById(R.id.nav_slider_header);

        image.buildDrawingCache();
        final Bitmap nav_slider_bitmap = image.getDrawingCache();

        image.setOnTouchListener(new OnTouchListener() {

            public boolean onTouch(View v, MotionEvent event) {
                // TODO Auto-generated method stub
                Bundle nav_slider_bundle = new Bundle();
                nav_slider_bundle.putParcelable("Nav_slider_image", nav_slider_bitmap);
                Movie nav_slider_product = nav_slider_movieitems.get(position);

                nav_slider_bundle.putParcelable("Navslidertitle", nav_slider_product);
                Intent intent = new Intent(nav_slider_activity, Category_Detail.class);
                intent.putExtras(nav_slider_bundle);
                nav_slider_activity.startActivity(intent);
                return false;
            }
        }); 

        Movie m = nav_slider_movieitems.get(position);
        image.setImageUrl(m.getThumbnailUrl(), nav_slider_imageLoader);

        nav_slider_title.setText(m.getTitle());

        return convertView;
    }


}

它抛出了这个错误..

    FATAL EXCEPTION: main
java.lang.NullPointerException
    at com.navslider.category.CategoryAdapter.getView(CategoryAdapter.java:61)
    at android.widget.AbsListView.obtainView(AbsListView.java:2177)
    at android.widget.ListView.makeAndAddView(ListView.java:1840)
...