android - 如何使用 volley 在 recyclerview 中填充 cardview - 它没有获取 JSON？

Question

我正在使用以下类，它们可以很好地处理静态数据。

这是我的 JSON 响应

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

这是我的 POJO 类

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;
    }

}

这是我的 CustomAdapter 类

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);
            }
        }

    }

这是我的 fragment 类

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;
    }
}

android moniter 给我这个:

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

您必须预先初始化您的 placesData 列表，然后使用它从您的 json 数组中添加对象。注意标有 //IMPORTANT!!! 的行:

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;
    }
}

此外，您不需要 onResponse 方法中的局部变量 placesArray