如何使用volley在recyclerview內部填充cardview - 它沒有獲取JSON？

Question

我正在使用以下類，它們與靜態數據工作正常。

這裏是我的JSON響應

[{"place_name":"Udon House"},{"place_name":"Casa Biance"},{"place_name":"Pizza hut"},{"place_name":"Pearl Continental "},{"place_name":"Lahore Meuseum"},{"place_name":"Shalimar Gardens"}] 

這是我的POJO類

public class places { 

    //Variable in json 

    public String place_name; 

    //Getters and setters 

    public String getPlace_name() { 
     return place_name; 
    } 

    public void setPlace_name(String name) { 
     this.place_name = name; 
    } 

} 

這是我CustomAdapter類

public class placesAdapter extends 
RecyclerView.Adapter<placesAdapter.ViewHolder> { 

     places places; 
    private Context context; 
     private List<places> places_list; 
    placesAPI p; 

     public placesAdapter(List<places> places) 
     { 
      this. places_list = places; 
     } 

     @Override 
     public placesAdapter.ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) { 
      View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.card_item, viewGroup, false); 
      return new ViewHolder(view); 
     } 

     @Override 
     public void onBindViewHolder(placesAdapter.ViewHolder viewHolder, int i) { 

      places_list.get(i); 

      viewHolder.place_name.setText(places_list.get(i).getPlace_name());    
     } 

     @Override 
     public int getItemCount() { 
      if (places_list != null) { 
       return places_list.size(); 
      } 
      return 0; 
     } 

     public class ViewHolder extends RecyclerView.ViewHolder{ 
      private TextView place_name; 

      public ViewHolder(View view) { 
       super(view); 

       place_name = (TextView)view.findViewById(R.id.tv_blah); 
      } 
     } 

    } 

這是我的片段類

public class BlankFragment extends Fragment { 
    List<places> placesData; 
    //placesAdapter adapter; 
    RecyclerView rv; 

    public BlankFragment() { 
     // 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 rootView = inflater.inflate(R.layout.fragment_blank, container, false); 

     rv = (RecyclerView) rootView.findViewById(R.id.rv_recycler_view); 
     rv.setHasFixedSize(true); 
     //RecyclerView.Adapter<String> adapter = new Adapter<>(getActivity(), R.layout.custom_tab); 


     LinearLayoutManager llm = new LinearLayoutManager(getActivity()); 
     rv.setLayoutManager(llm); 


    final placesAdapter rvAdapter = new placesAdapter(getActivity(), placesData); 
     rv.setAdapter(rvAdapter); 
     RequestQueue requestQueue = Volley.newRequestQueue(getActivity()); 
     String url = "http://192.168.10.5/tourist/placeTest.php"; 

     JsonArrayRequest req = new JsonArrayRequest(url, 
       new Response.Listener<JSONArray>() { 
        @Override 
        public void onResponse(JSONArray response) { 
         Log.d(TAG, response.toString()); 

         try { 

          List<places> placesArray = new ArrayList<places>(); 

          JSONArray jsonArray = response.getJSONArray(response.toString()); 

          for (int i = 0; i < response.length(); i++) { 

           JSONObject placeObject = jsonArray.getJSONObject(i); 
           places p = new places(); 
           p.place_name = placeObject.getString("place_name"); 
           placesArray.add(p); 
          } 

          rvAdapter.notifyDataSetChanged(); 

         } 
         catch (JSONException e) { 
          e.printStackTrace(); 
         } 


        } 
       }, new Response.ErrorListener() { 
      @Override 
      public void onErrorResponse(VolleyError error) { 
       VolleyLog.d(TAG, "Error: " + error.getMessage()); 
      } 
     }); 
     requestQueue.add(req); 
     // Adding request to request queue 
     return rootView; 
    } 
} 

的Android箴言報是給我這樣的：

07-25 12:59:00.048 830-830/? E/NetworkScheduler.SR: Invalid package name : Perhaps you didn't include a PendingIntent in the extras? 
07-25 12:59:00.923 513-572/? E/KeyguardUpdateMonitor: Object tried to add another callback 
                 java.lang.Exception: Called by 
                  at com.android.internal.policy.impl.keyguard.KeyguardUpdateMonitor.registerCallback(KeyguardUpdateMonitor.java:1107) 
                  at com.android.internal.policy.impl.keyguard.KeyguardSelectorView.onResume(KeyguardSelectorView.java:331) 
                  at com.android.internal.policy.impl.keyguard.KeyguardHostView.onScreenTurnedOn(KeyguardHostView.java:1118) 
                  at com.android.internal.policy.impl.keyguard.KeyguardViewManager.onScreenTurnedOn(KeyguardViewManager.java:404) 
                  at com.android.internal.policy.impl.keyguard.KeyguardViewMediator.handleNotifyScreenOn(KeyguardViewMediator.java:1767) 
                  at com.android.internal.policy.impl.keyguard.KeyguardViewMediator.access$2300(KeyguardViewMediator.java:106) 
                  at com.android.internal.policy.impl.keyguard.KeyguardViewMediator$4.handleMessage(KeyguardViewMediator.java:1413) 
                  at android.os.Handler.dispatchMessage(Handler.java:107) 
                  at android.os.Looper.loop(Looper.java:194) 
                  at android.os.HandlerThread.run(HandlerThread.java:60) 
07-25 12:59:00.935 135-9746/? E/AudioMTKHardware: setParameters() still have param.size() = 1, remain param = "screen_state=on" 
07-25 12:59:05.455 22623-22623/? E/dalvikvm: Could not find class 'android.app.AppOpsManager', referenced from method com.google.android.gms.common.GooglePlayServicesUtil.a 
07-25 12:59:06.122 20191-21273/? E/dalvikvm: Could not find class 'android.telephony.CellInfoWcdma', referenced from method nqp.a 
07-25 12:59:06.196 22623-22623/? E/dalvikvm: Could not find class 'com.facebook.common.jobscheduler.compat.JobServiceCompat', referenced from method com.facebook.common.jobscheduler.compat.ServiceInfoParser.<init> 
07-25 12:59:06.846 22603-22603/? E/dalvikvm: Could not find class 'android.content.pm.LauncherApps', referenced from method com.google.android.apps.gsa.search.shared.multiuser.l.connect 
07-25 12:59:06.993 20191-21273/? E/dalvikvm: Could not find class 'android.telephony.CellInfoWcdma', referenced from method nqp.c 
07-25 12:59:07.369 20191-21273/? E/dalvikvm: Could not find class 'android.telephony.CellInfoWcdma', referenced from method nqq.a 
07-25 12:59:10.201 22674-22674/com.nuku.mc.populate_recyclerview E/AndroidRuntime: FATAL EXCEPTION: main 
                        java.lang.NullPointerException 
                         at com.nuku.mc.populate_recyclerview.BlankFragment$1.onResponse(BlankFragment.java:79) 
                         at com.nuku.mc.populate_recyclerview.BlankFragment$1.onResponse(BlankFragment.java:64) 
                         at com.android.volley.toolbox.JsonRequest.deliverResponse(JsonRequest.java:65) 
                         at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99) 
                         at android.os.Handler.handleCallback(Handler.java:800) 
                         at android.os.Handler.dispatchMessage(Handler.java:100) 
                         at android.os.Looper.loop(Looper.java:194) 
                         at android.app.ActivityThread.main(ActivityThread.java:5371) 
                         at java.lang.reflect.Method.invokeNative(Native Method) 
                         at java.lang.reflect.Method.invoke(Method.java:525) 
                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833) 
                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600) 
                         at dalvik.system.NativeStart.main(Native Method) 
07-25 12:59:10.348 513-574/? E/AppErrorDialog: Failed to get ILowStorageHandle instance 
07-25 12:59:11.632 513-811/? E/CellLocation: create GsmCellLocation 
07-25 12:59:11.651 513-571/? E/CellLocation: create GsmCellLocation 
07-25 12:59:11.663 843-1303/? E/CellLocation: create GsmCellLocation 
07-25 12:59:11.704 513-571/? E/CellLocation: create GsmCellLocation 

Answer 1

你必須事先和使用初始化placesData名單它用於稍後添加來自json數組的對象。注意標有// IMPORTANT!!!行：

public class BlankFragment extends Fragment { 
    List<places> placesData = new ArrayList<>(); // IMPORTANT!!! 

    //... 
     JsonArrayRequest req = new JsonArrayRequest(url, 
       new Response.Listener<JSONArray>() { 
        @Override 
        public void onResponse(JSONArray response) { 
         Log.d(TAG, response.toString()); 

         try { 
          for (int i = 0; i < response.length(); i++) { 
           JSONObject placeObject = jsonArray.getJSONObject(i); 
           places p = new places(); 
           p.place_name = placeObject.getString("place_name"); 
           placesData.add(p); // IMPORTANT!!! 
          } 

          rvAdapter.notifyDataSetChanged(); 

         } 
         catch (JSONException e) { 
          e.printStackTrace(); 
         } 


        } 
       }, new Response.ErrorListener() { 
      @Override 
      public void onErrorResponse(VolleyError error) { 
       VolleyLog.d(TAG, "Error: " + error.getMessage()); 
      } 
     }); 
     requestQueue.add(req); 
     return rootView; 
    } 
} 

而且你不需要在onResponse方法

Answer 2

試試這個方法，並檢查是否你得到你的JsonArray正確的日誌：

 public void getJsonArray() 
       { 
        String url = "http://192.168.10.5/tourist/placeTest.php"; 

        JsonArrayRequest req = new JsonArrayRequest(url, 
          new Response.Listener<JSONArray>() { 
           @Override 
           public void onResponse(JSONArray response) { 
            Log.d(TAG, response.toString()); 

            List<String> placesArray= new ArrayList<String>(); 

            JSONArray jsonArray = response.getJSONArray(response.toString()); 

            for (int i=0; i<cast.length(); i++) { 

            JSONObject placeObject = jsonArray.getJSONObject(i); 
            String name = placeObject.getString("place_name"); 
            placesArray.add(name); 
            } 

           } 
          }, new Response.ErrorListener() { 
         @Override 
         public void onErrorResponse(VolleyError error) { 
          VolleyLog.d(TAG, "Error: " + error.getMessage()); 
          pDialog.hide(); 
         } 
        }); 

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