Question

我使用php语言在我自己的网站上Volley（Tablayout经理）请求Fragment。我正在检查网址，网络没有问题。但是当我在Volley内拨打Fragment时，它无法正常工作并在我打电话时显示错误 adapter.notifyDataSetChanged（）;

这是 TabOneFragment.java

public class TabOneFragment extends Fragment implements SearchView.OnQueryTextListener {

public RecyclerView recyclerView;
public static AlbumsAdapter adapter;
public static List<Album> albumList;

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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        db = new Db(getActivity());

        View view = inflater.inflate(R.layout.tab_one_fragment, container, false);


final RecyclerView.LayoutManager mLayoutManager = new GridLayoutManager(getActivity(), 2);
        recyclerView.setLayoutManager(mLayoutManager);
        recyclerView.addItemDecoration(new GridSpacingItemDecoration(2, dpToPx(5), true));
        recyclerView.setItemAnimator(new DefaultItemAnimator());
        recyclerView.setAdapter(adapter);

        RequestQueue requestQueue = Volley.newRequestQueue(getActivity().getApplicationContext());

        StringRequest stringRequest = new StringRequest(Request.Method.POST, booking,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {

                        if (response.equals("{\"DSMON\":null}")) {

                        } else

                            try {


                                JSONObject jsonRootObject = new JSONObject(response);
                                JSONArray jsonArray = jsonRootObject.optJSONArray("DSMON");

                                for (int i = 0; i < jsonArray.length(); i++) {
                                    JSONObject jsonObject = jsonArray.getJSONObject(i);
                                    boolean check = false;
                                    IDmon = jsonObject.optString("ID");
                                    IDcuahang = jsonObject.optString("IDCH");
                                    Tenmon = jsonObject.optString("TenMon");
                                    Gia = jsonObject.optString("Gia");
                                    Imgurl = jsonObject.optString("ImgUrl");
                                    String imgname = Imgurl.substring(Imgurl.lastIndexOf("/") + 1);
                                    Album a = new Album(IDmon, Tenmon, Gia, imgname, Imgurl);

// Error at line bellow, because volley respone empty

                                    albumList.add(a);
                                    adapter.notifyDataSetChanged();

                                    ds.close();
                                    tt = true;

                                }


                            } catch (JSONException e) {
                                e.printStackTrace();
                            }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Log.d("Lỗi", "Lỗi" + "\n" + error.toString());
                    }


                }) {

        };
        requestQueue.add(stringRequest);

        return view;


    }

这是 logcat 文件：

  E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.example.hieul.hismartversearch, PID: 13281
                  java.lang.NullPointerException: Attempt to invoke virtual method 'void com.example.hieul.hismartversearch.AlbumsAdapter.notifyDataSetChanged()' on a null object reference
                      at com.example.hieul.hismartversearch.TabOneFragment$1.onResponse(TabOneFragment.java:169)
                      at com.example.hieul.hismartversearch.TabOneFragment$1.onResponse(TabOneFragment.java:143)
                      at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:60)
                      at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:30)
                      at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99)
                      at android.os.Handler.handleCallback(Handler.java:739)
                      at android.os.Handler.dispatchMessage(Handler.java:95)
                      at android.os.Looper.loop(Looper.java:158)
                      at android.app.ActivityThread.main(ActivityThread.java:7225)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Application terminated.

Answer 1

首先在调用API之前初始化albumList，如下所示。

albumList=new ArrayList<Album>;

在片段错误中调用Volley

1 个答案: