Hola soy principiante en anroid. Creé cajones de navegación y fragmentos. Puedo obtener datos de json con url. Funciona mientras está en línea. Pero cuando estoy fuera de línea, recibo el error "no se puede resolver el host". Quiero obtener datos de url con json mientras estoy desconectado. No es cachéingrese la descripción de la imagen aquí

fragmento

private static final String jsonUrl = "http://sunumsitesi.com/json.php";
private ProgressDialog pDialog;
private List<Urun> urunList = new ArrayList<Urun>();
private ListView listView;
private CustomListAdapter adapter;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
    View root = inflater.inflate(R.layout.fragment_yemek, container, false);
    return root;
}
@Override
public void onActivityCreated(Bundle savedInstanceState)
{
    super.onActivityCreated(savedInstanceState);
    View v = getView();
    if(v!=null)
    {
        listView = (ListView) v.findViewById(R.id.yemekList);
        adapter = new CustomListAdapter(getActivity(), urunList);
        listView.setAdapter(adapter);

        pDialog = new ProgressDialog(getActivity());
        pDialog.setMessage("Loading...");
        pDialog.show();
        JsonArrayRequest urunReq = new JsonArrayRequest(jsonUrl, new Response.Listener<JSONArray>()
        {
            @Override
            public void onResponse(JSONArray response)
            {
                hidePDialog();
                for (int i = 0; i < response.length(); i++)
                {
                    try
                    {

                        JSONObject obj = response.getJSONObject(i);
                        Urun urun = new Urun();
                        urun.setUrun_adi(obj.getString("urun_adi"));
                        urun.setUrl("http://www.iremdeveci.com/ornekler/resimler/resim.png");//example
                        urunList.add(urun);
                    } catch (JSONException ex)
                    {
                        ex.printStackTrace();
                    }
                }
                adapter.notifyDataSetChanged();
            }
        }, new Response.ErrorListener()
        {
            @Override
            public void onErrorResponse(VolleyError volleyError)
            {
                Toast.makeText(getActivity(), volleyError.getMessage(), Toast.LENGTH_LONG).show();
            }
        });
        AppController.getmInstance().addToRequestQueue(urunReq);
    }
}

@Override
public void onDestroy()
{
    super.onDestroy();
    hidePDialog();
}
private void hidePDialog()
{
    if(pDialog!=null)
    {
        pDialog.dismiss();
        pDialog=null;
    }
}

y CustomListAdapter (extender BaseAdapter)

private Activity activity;
private LayoutInflater inflater;
private List<Urun> urunItems;
ImageLoader imageLoader = AppController.getmInstance().getmImageLoader();
public CustomListAdapter(Activity activity,List<Urun> urunItems)
{
    this.activity=activity;
    this.urunItems=urunItems;
}

@Override
public int getCount()
{
    return urunItems.size();
}

@Override
public Object getItem(int location)
{
    return urunItems.get(location);
}

@Override
public long getItemId(int position)
{
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent)
{
    if (inflater==null)
    {
        inflater=(LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }
    if (convertView==null)
    {
        convertView=inflater.inflate(R.layout.list_row,null);
    }
    if (imageLoader==null)
    {
        imageLoader=AppController.getmInstance().getmImageLoader();
    }
    NetworkImageView urunResim=(NetworkImageView)convertView.findViewById(R.id.urunResim);
    TextView urun_adi= (TextView)convertView.findViewById(R.id.urun_adi);
    Urun u = urunItems.get(position);

    urunResim.setImageUrl(u.getUrl(),imageLoader);
    urun_adi.setText(u.getUrun_adi());
    return convertView;
}

LruBitmapCache.java

public static int getDefaultLruCacheSize()
{
    final int maxMemory=(int)(Runtime.getRuntime().maxMemory()/1024);
    final int cacheSize= maxMemory/8;
    return cacheSize;
}
public LruBitmapCache()
{
    this(getDefaultLruCacheSize());
}
public LruBitmapCache(int sizeInKiloBytes)
{
    super(sizeInKiloBytes);
}

@Override
protected int sizeOf(String key, Bitmap value)
{
    return value.getRowBytes() * value.getHeight()/1024;
}

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

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