Null pointer exception in volley singleton

I've copied the volleySingleton code from developer.android.com and tried to get an image from a URL in a recycler view, but at the time of loading data app crashes. I've tried some fixes but they haven't worked

Here is the volleySingleton class copied from developer.android.com

public class MyApplication extends Application {
    private static MyApplication mInstance;
    private RequestQueue mRequestQueue;
    private ImageLoader mImageLoader;
    private static Context mCtx;

    private MyApplication(Context context) {
        mCtx = context;
        mRequestQueue = getRequestQueue();

        mImageLoader = new ImageLoader(mRequestQueue,
                new ImageLoader.ImageCache() {
                    private final LruCache<String, Bitmap>
                            cache = new LruCache<String, Bitmap>(20);

                    @Override
                    public Bitmap getBitmap(String url) {
                        return cache.get(url);
                    }

                    @Override
                    public void putBitmap(String url, Bitmap bitmap) {
                        cache.put(url, bitmap);
                    }
                });
    }

    public static synchronized MyApplication getInstance(Context context) {
        if (mInstance == null) {
            mInstance = new MyApplication(context);
        }
        return mInstance;
    }

    public RequestQueue getRequestQueue() {
        if (mRequestQueue == null) {
            // getApplicationContext() is key, it keeps you from leaking the
            // Activity or BroadcastReceiver if someone passes one in.
            mRequestQueue = Volley.newRequestQueue(mCtx.getApplicationContext());
        }
        return mRequestQueue;
    }

    public <T> void addToRequestQueue(Request<T> req) {
        getRequestQueue().add(req);
    }

    public ImageLoader getImageLoader() {
        return mImageLoader;
    }
}

Here is the logcat report

java.lang.NullPointerException
at com.aninesoft.meltwishbeta.MyApplication.getRequestQueue(MyApplication.java:61)
at com.aninesoft.meltwishbeta.MyApplication.(MyApplication.java:31)
at com.aninesoft.meltwishbeta.MyApplication.getInstance(MyApplication.java:52)
at com.aninesoft.meltwishbeta.RecyclerViewDataAdapter.onBindViewHolder(RecyclerViewDataAdapter.java:45)
at com.aninesoft.meltwishbeta.RecyclerViewDataAdapter.onBindViewHolder(RecyclerViewDataAdapter.java:19)
at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:5277)
at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:5310)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4568)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4461)
at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:1962)
at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1371)
at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1334)
at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:563)
at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:2847)
at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3145)
at android.view.View.layout(View.java:14832)
at android.view.ViewGroup.layout(ViewGroup.java:4640)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
at android.view.View.layout(View.java:14832)
at android.view.ViewGroup.layout(ViewGroup.java:4640)
at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1627)
at android.view.View.layout(View.java:14832)
at android.view.ViewGroup.layout(ViewGroup.java:4640)
at android.support.design.widget.CoordinatorLayout.layoutChild(CoordinatorLayout.java:1034)
at android.support.design.widget.CoordinatorLayout.onLayoutChild(CoordinatorLayout.java:744)
at android.support.design.widget.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:42)
at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1180)
at android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:757)
at android.view.View.layout(View.java:14832)
at android.view.ViewGroup.layout(ViewGroup.java:4640)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
at android.view.View.layout(View.java:14832)
at android.view.ViewGroup.layout(ViewGroup.java:4640)
at android.support.v7.internal.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:437)
at android.view.View.layout(View.java:14832)
at android.view.ViewGroup.layout(ViewGroup.java:4640)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
at android.view.View.layout(View.java:14832)
at android.view.ViewGroup.layout(ViewGroup.java:4640)
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:14832)
at android.view.ViewGroup.layout(ViewGroup.java:4640)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
at android.view.View.layout(View.java:14832)
at android.view.ViewGroup.layout(ViewGroup.java:4640)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1996)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1753)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1004)
at android.view.ViewRootImpl$

Here is the adapter class

public class RecyclerViewDataAdapter extends RecyclerView.Adapter<RecyclerViewDataAdapter.ViewHolder> {
    private Context context;
    public ImageLoader mImageLoader;

    //List of superHeroes
    List<ListOfData> superHeroes;

    public RecyclerViewDataAdapter(List<ListOfData> superHeroes, Context context){
        super();
        //Getting all the superheroes
        this.superHeroes = superHeroes;
        this.context=context;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.recyclerview_row, parent, false);
        ViewHolder viewHolder = new ViewHolder(v);
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        ListOfData superHero =  superHeroes.get(position);

        mImageLoader = MyApplication.getInstance(context).getImageLoader();
        mImageLoader.get(superHero.getImageUrl(), ImageLoader.getImageListener(holder.imageView1, R.mipmap.ic_launcher, android.R.drawable.ic_dialog_alert));

        holder.imageView1.setImageUrl(superHero.getImageUrl(), mImageLoader);
        holder.textViewName1.setText(superHero.getName());
        //holder.textViewRank.setText(String.valueOf(superHero.getRank()));
        //holder.textViewRealName.setText(superHero.getRealName());
        //holder.textViewCreatedBy.setText(superHero.getCreatedBy());
        //holder.textViewFirstAppearance.setText(superHero.getFirstAppearance());

        String powers = "";

       /* for(int i = 0; i<superHero.getPowers().size(); i++){
            powers+= superHero.getPowers().get(i);
        }*/

        //holder.textViewPowers.setText(powers);

    }

    @Override
    public int getItemCount() {
        return superHeroes.size();
    }

    class ViewHolder extends RecyclerView.ViewHolder{
        public NetworkImageView imageView1;
        public NetworkImageView imageView2;
        public TextView textViewName1;
        public TextView textViewName2;
        public TextView textViewRank;
        public TextView textViewRealName;
        public TextView textViewCreatedBy;
        public TextView textViewFirstAppearance;
        public TextView textViewPowers;

        public ViewHolder(View itemView) {
            super(itemView);
            imageView1 = (NetworkImageView) itemView.findViewById(R.id.imageViewHero);
            //imageView2 = (NetworkImageView) itemView.findViewById(R.id.thumbnail2);
           textViewName1 = (TextView) itemView.findViewById(R.id.textViewName);//textViewName2 = (TextView) itemView.findViewById(R.id.category_title_two);
            /* textViewRank= (TextView) itemView.findViewById(R.id.textViewRank);
            textViewRealName= (TextView) itemView.findViewById(R.id.textViewRealName);
            textViewCreatedBy= (TextView) itemView.findViewById(R.id.textViewCreatedBy);
            textViewFirstAppearance= (TextView) itemView.findViewById(R.id.textViewFirstAppearance);
            textViewPowers= (TextView) itemView.findViewById(R.id.textViewPowers);
            */
        }
    }
}

and Json part

    public class Pants extends Fragment {

    //Creating a List of superheroes

    public Context context;
    public List<ListOfData> listSuperHeroes;

    //Creating Views
    private RecyclerView recyclerView;
    private RecyclerView.LayoutManager layoutManager;
    private RecyclerView.Adapter adapter;


    public Pants() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.tshirts_pants_shirts, container, false);

        recyclerView = (RecyclerView) view.findViewById(R.id.recycler_view);
        layoutManager = new LinearLayoutManager(getActivity().getApplicationContext());
        recyclerView.setLayoutManager(layoutManager);

        //Calling method to get data
        getData();
        return view;
    }


    private void getData() {
        //Showing a progress dialog
        final ProgressDialog loading = ProgressDialog.show(getActivity(), "Loading Data", "Please wait...", false, false);

        //Creating a json array request
        JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(ProductConfig.DATA_URL,

                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        //Dismissing progress dialog
                        loading.dismiss();

                        //calling method to parse json array
                        parseData(response);
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {

                    }
                });

        //Creating request queue
        RequestQueue requestQueue = Volley.newRequestQueue(getActivity());

        //Adding request to the queue
        requestQueue.add(jsonArrayRequest);
    }

    //This method will parse json data
    private void parseData(JSONArray array) {
        listSuperHeroes = new ArrayList<>();
        for (int i = 0; i < array.length(); i++) {
            ListOfData superHero = new ListOfData();
            JSONObject json = null;
            try {
                json = array.getJSONObject(i);
                superHero.setImageUrl(json.getString(ProductConfig.TAG_IMAGE_URL));
                superHero.setName(json.getString(ProductConfig.TAG_NAME));
                /*superHero.setRank(json.getInt(ProductConfig.TAG_RANK));
                superHero.setRealName(json.getString(ProductConfig.TAG_REAL_NAME));
                superHero.setCreatedBy(json.getString(ProductConfig.TAG_CREATED_BY));
                superHero.setFirstAppearance(json.getString(ProductConfig.TAG_FIRST_APPEARANCE));
                */

                ArrayList<String> powers = new ArrayList<String>();

                JSONArray jsonArray = json.getJSONArray(ProductConfig.TAG_POWERS);

                for (int j = 0; j < jsonArray.length(); j++) {
                    powers.add(((String) jsonArray.get(j)) + "n");
                }
                superHero.setPowers(powers);


            } catch (JSONException e) {
                e.printStackTrace();
            }
            listSuperHeroes.add(superHero);
        }
        adapter = new RecyclerViewDataAdapter(listSuperHeroes, context);

        //Adding adapter to recyclerview
        recyclerView.setAdapter(adapter);
        //Initializing our superheroes list



    }
}

链接地址: http://www.djcxy.com/p/93158.html

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