Question

这是我的片段类

public class Frangment_electronics extends Fragment {
    private static final String TAG = "RecyclerViewExample";
    private RecyclerView mRecyclerView;
    private RecyclerAdapter adapter;
    private List<Listdetails> listdetails=new ArrayList<Listdetails>();
    private static final String Url = "http://onam.leah.in/new/item_details.php";
    private ProgressDialog progressDialog;

    public Frangment_electronics(){}



    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_electronics, container, false);
        mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recycler_view);

        final LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
        mRecyclerView.setLayoutManager(linearLayoutManager);
        adapter = new RecyclerAdapter(getActivity(), listdetails);
        mRecyclerView.setAdapter(adapter);

        RequestQueue queue = Volley.newRequestQueue(getActivity());


        showPD();


        JsonArrayRequest movieReq1 = new JsonArrayRequest(Url,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        Log.d(TAG, response.toString());
                        hidePD();

                        // Parsing json
                        for (int i = 0; i < response.length(); i++) {
                            try {

                                JSONObject obj = response.getJSONObject(i);

                                 Listdetails item = new Listdetails();
                                 item.setPhone_name(obj.getString("Phone"));
                                item.setPrice(obj.getString("Price"));
                                item.setThumbnail(obj.getString("Image"));



                                listdetails.add(item);

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

                        }


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

            }
        });


        queue.add(movieReq1);
        return rootView;
    }
    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);


    }






    private void showPD() {
        if(progressDialog == null) {
            progressDialog  = new ProgressDialog(getActivity());
            progressDialog .setMessage("Loading...");
            progressDialog .setCancelable(false);
            progressDialog .setCanceledOnTouchOutside(false);
            progressDialog .show();
        }
    }


    private void hidePD() {
        if (progressDialog  != null) {
            progressDialog .dismiss();
            progressDialog  = null;
        }
    }


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

我收到以下错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.content.Context.getApplicationContext()' on a null object reference at 
info.androidhive.Groupdeal.app.MySingleton.getRequestQueue(MySingleton.java:61) at info.androidhive.Groupdeal.app.MySingleton.<init>(MySingleton.java:26)

Answer 1

final LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
RequestQueue queue = Volley.newRequestQueue(getActivity());

将getActivity（）替换为上面几行中的rootView.getContext（）。您还有许多其他地方使用过getActivity（）。用rootView.getContext（）替换它们。在片段中，您不能直接调用活动，而是必须使用与布局inflater创建的视图关联的任何上下文。

编辑：将showPD（）代码更改为此

private void showPD(Context context) {
    if(progressDialog == null) {
        progressDialog  = new ProgressDialog(context);
        progressDialog .setMessage("Loading...");
        progressDialog .setCancelable(false);
        progressDialog .setCanceledOnTouchOutside(false);
        progressDialog .show();
    }
}

并像这样称呼它

Context context = rootView.getContext;
showPD(context);

嗨。我试图在我的片段旁边实现回收站视图但不幸的是应用程序崩溃了

1 个答案: