Parse Json Von URL

Question

Ich versuche, JSON von einer URL in einem Listview zu analysieren, aber es zeigt einen Fehler

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'com.android.volley.toolbox.ImageLoader com.example.vijaypremi.acmeoopsfood.util.AppController.getImageLoader()' on a null object reference 
    at com.example.vijaypremi.acmeoopsfood.adapter.CustomListAdapter.<init>(CustomListAdapter.java:26) 
    at com.example.vijaypremi.acmeoopsfood.MainActivity.onCreate(MainActivity.java:44) 
    at android.app.Activity.performCreate(Activity.java:5990) 
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106) 

Meine Haupttätigkeit ist:

public class MainActivity extends Activity { 

    // Log tag 
    private static final String TAG = MainActivity.class.getSimpleName(); 

    // Billionaires json url 
    private static final String url = "http://ibookstay.com/oops/restapi/all-restaurant"; 
    private ProgressDialog pDialog; 
    private List<RestaurentInfo> RestaurentInfoList = new ArrayList<RestaurentInfo>(); 
    private ListView listView; 
    private CustomListAdapter adapter; 
    String in; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     listView = (ListView) findViewById(R.id.list); 
     adapter = new CustomListAdapter(this, RestaurentInfoList); 
     listView.setAdapter(adapter); 

     pDialog = new ProgressDialog(this); 
     // Showing progress dialog before making http request 
     pDialog.setMessage("Loading..."); 
     pDialog.show(); 

     // Creating volley request obj 
     final JsonArrayRequest reqqueue = new JsonArrayRequest(url, 
       new Response.Listener<JSONArray>() { 
        @Override 
        public void onResponse(JSONArray response) { 
         Log.d(TAG, response.toString()); 
         hidePDialog(); 
         // Parsing json 
         try { 
          JSONObject jsonRootObject = new JSONObject(url); 

          //Get the instance of JSONArray that contains JSONObjects 
          JSONArray mainnode =jsonRootObject.getJSONArray("data"); 

          //Iterate the jsonArray and print the info of JSONObjects 
          for(int i=0; i < mainnode.length(); i++){ 
           JSONObject jsonObject = mainnode.getJSONObject(i); 
           JSONObject data = jsonObject.getJSONObject("restaurentInfo"); 

           RestaurentInfo restaurentinfo = new RestaurentInfo(); 
           restaurentinfo.setRestaurent_name(data.getString("restaurent_name")); 
           restaurentinfo.setRestaurent_logo(data.getString("restaurent_logo")); 
           restaurentinfo.setRestaurent_phone_number(data.getString("restaurent_phone_number")); 
           restaurentinfo.setRestaurent_bussiness_owner_name(data.getString("restaurent_bussiness_owner_name")); 
           restaurentinfo.setRestaurent_email(data.getString("restaurent_email")); 



          } 
          Log.d(TAG, "onResponse: "); 
         } catch (JSONException e) {e.printStackTrace();} 


         // notifying list adapter about data changes 
         // so that it renders the list view with updated data 
         adapter.notifyDataSetChanged(); 
        } 
       }, new Response.ErrorListener() { 
      @Override 
      public void onErrorResponse(VolleyError error) { 
       VolleyLog.d(TAG, "Error: " + error.getMessage()); 
       hidePDialog(); 
      } 
     }); 

     // Adding request to request queue 
     AppController.getInstance().addToRequestQueue(reqqueue); 
    } 

    @Override 
    public void onDestroy() { 
     super.onDestroy(); 
     hidePDialog(); 
    } 

    private void hidePDialog() { 
     if (pDialog != null) { 
      pDialog.dismiss(); 
      pDialog = null; 
     } 
    } 

} 

And My CustomListAdapter ist:

public class CustomListAdapter extends BaseAdapter { 

    private Activity activity; 
    private LayoutInflater inflater; 
    private List<RestaurentInfo> restaurentinfo; 
    ImageLoader imageLoader = AppController.getInstance().getImageLoader(); 

    public CustomListAdapter(Activity activity, List<RestaurentInfo> restaurentinfo) { 
     this.activity = activity; 
     this.restaurentinfo = restaurentinfo; 
    } 

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

    @Override 
    public Object getItem(int location) { 
     return restaurentinfo.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.getInstance().getImageLoader(); 
     NetworkImageView thumbNail = (NetworkImageView) convertView 
       .findViewById(R.id.thumbnail); 
     TextView name = (TextView) convertView.findViewById(R.id.name); 
     TextView worth = (TextView) convertView.findViewById(R.id.worth); 
     TextView source = (TextView) convertView.findViewById(R.id.source); 
     TextView year = (TextView) convertView.findViewById(R.id.inYear); 

     // getting billionaires data for the row 
     RestaurentInfo m = restaurentinfo.get(position); 

     // thumbnail image 
     thumbNail.setImageUrl(m.getRestaurent_logo(), imageLoader); 

     // name 
     name.setText(m.getRestaurent_name()); 

     // Wealth Source 
     source.setText("Wealth Source: " + String.valueOf(m.getRestaurent_info_id())); 


     worth.setText(String.valueOf(m.getRestaurent_phone_number())); 

     // release year 
     year.setText(String.valueOf(m.getRestaurent_email())); 

     return convertView; 
    } 

} 

Für Anforderungswarteschlange und Bild Loader i AppController erstellt haben:

public class AppController extends Application { 

    public static final String TAG = AppController.class.getSimpleName(); 

     private RequestQueue mRequestQueue; 
     private ImageLoader mImageLoader; 

     private static AppController mInstance; 

     @Override 
     public void onCreate() { 
      super.onCreate(); 
      mInstance = this; 
     } 

     public static synchronized AppController getInstance() { 
      return mInstance; 
     } 

     public RequestQueue getRequestQueue() { 
      if (mRequestQueue == null) { 
       mRequestQueue = Volley.newRequestQueue(getApplicationContext()); 
      } 

      return mRequestQueue; 
     } 

     public ImageLoader getImageLoader() { 
      getRequestQueue(); 
      if (mImageLoader == null) { 
       mImageLoader = new ImageLoader(this.mRequestQueue, 
         new LruBitmapCache()); 
      } 
      return this.mImageLoader; 
     } 

     public <T> void addToRequestQueue(Request<T> req, String tag) { 
      // set the default tag if tag is empty 
      req.setTag(TextUtils.isEmpty(tag) ? TAG : tag); 
      getRequestQueue().add(req); 
     } 

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

     public void cancelPendingRequests(Object tag) { 
      if (mRequestQueue != null) { 
       mRequestQueue.cancelAll(tag); 
      } 
     } 
    } 

Answer 1

Ihre Anfrage Objekt möglicherweise Daten abruft - aber Sie verwenden es nicht in der OnResponse überschreiben.

Dies muss die Antwort verwenden.

// Creating volley request obj 
final JsonArrayRequest reqqueue = new JsonArrayRequest(url, 
     new Response.Listener<JSONArray>() { 
      @Override 
      public void onResponse(JSONArray response) { 
       Log.d(TAG, response.toString()); 
       hidePDialog(); 
       // Parsing json 
       try { 
     /*** you wanna use the response here... ***/ 
        JSONObject jsonRootObject = new JSONObject(url); 

        //Get the instance of JSONArray that contains JSONObjects 
        JSONArray mainnode =jsonRootObject.getJSONArray("data"); 

        //Iterate the jsonArray and print the info of JSONObjects 
        for(int i=0; i < mainnode.length(); i++){ 
         JSONObject jsonObject = mainnode.getJSONObject(i); 
         JSONObject data = jsonObject.getJSONObject("restaurentInfo"); 

         RestaurentInfo restaurentinfo = new RestaurentInfo(); 
         restaurentinfo.setRestaurent_name(data.getString("re 

Answer 2

Zuerst müssen Sie diese Klasse im Manifest

<application 
     android:name=".AppController" 

dann erklären, ob das funktioniert. Sie müssen die Instanz in die andere Instanz bringen.

public class CustomListAdapter extends BaseAdapter { 
    ....... 
    ImageLoader imageLoader; 

    public CustomListAdapter(Activity activity, List<RestaurentInfo> restaurentinfo) { 
     this.activity = activity; 
     this.restaurentinfo = restaurentinfo; 
     this.imageLoader = AppController.getInstance().getImageLoader(); 
    }