Android Cardview 和 Recycler 与 Volley 发生错误

我有一些代码可以使用 Volley 将 JSON 数据解析为cardview 和recycler。我想将 json 数据显示到我的片段中。我收到错误，但我不知道是什么原因造成的。也许任何人都可以帮助我。

这是我的片段。

public class HomeFragment extends android.support.v4.app.Fragment {
  private static final String TAG = HomeActivity.class.getSimpleName();
  private ArrayList<ListItem> listItems;

  @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_home, container, false);

    ParseData();

    RecyclerView recyclerView = (RecyclerView) getActivity().findViewById(R.id.recycler_list);
    recyclerView.setHasFixedSize(true);
    recyclerView.setAdapter(new ListCardAdapter(listItems, R.layout.report_list_item));

    recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
    recyclerView.setLayoutManager(new GridLayoutManager(getActivity(),2));
    recyclerView.setItemAnimator(new DefaultItemAnimator());


    // Inflate the layout for this fragment
    return rootView;
}

private void ParseData(){
    JsonArrayRequest listReq = new JsonArrayRequest(AppConfig.URL_LIST,
            new Response.Listener<JSONArray>() {
                @Override
                public void onResponse(JSONArray response) {
                    Log.d(TAG, response.toString());

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

                            JSONObject obj = response.getJSONObject(i);
                            ListItem listItem = new ListItem();
                            listItem.setDesc(obj.getString("desc"));

                            String image = obj.isNull("image") ? null : obj.getString("image");
                            listItem.setImge(image);

                            // adding movie to movies array
                            listItems.add(listItem);

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

                    }


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

    // Adding request to request queue
    VolleyController.getInstance().addToRequestQueue(listReq);
}

这是我的适配器。

public class ListCardAdapter extends RecyclerView.Adapter<ListCardAdapter.ViewHolder> {
private final String TAG = this.getClass().getSimpleName();
private List<TerbaruItem> terbaruItems;
private int itemLayout;
ImageLoader imageLoader = VolleyController.getInstance().getImageLoader();

public ListCardAdapter(List<ListItem> data, int itemLayout){
    listItems = data;
    this.itemLayout = itemLayout;
}

public static class ViewHolder extends RecyclerView.ViewHolder implements AdapterView.OnClickListener {

    public ReportImageView image;
    public TextView desc;

    public ViewHolder(View itemView) {

        super(itemView);

        itemView.setOnClickListener(this);
        image = (ReportImageView) itemView.findViewById(R.id.image);
        desc = (TextView) itemView.findViewById(R.id.desc);
    }

    @Override
    public void onClick(View view) {
        Toast.makeText(view.getContext(), "OnItemClick :D", Toast.LENGTH_SHORT).show();
    }

}

@Override
public ViewHolder onCreateViewHolder(ViewGroup  parent, int i) {

    View itemLayoutView = LayoutInflater.from(parent.getContext()).inflate(itemLayout, parent, false);
    ViewHolder viewHolder = new ViewHolder(itemLayoutView);
    return viewHolder;

}

@Override
public void onBindViewHolder(ViewHolder viewHolder, int position) {

    ListItem listItem = listItems.get(position);
    viewHolder.desc.setText(listItem.getDesc());


    // Feed image
    if (listItem.getImge() != null) {
        viewHolder.image.setImageUrl(listItem.getImge(), imageLoader);
        viewHolder.image.setVisibility(View.VISIBLE);
        viewHolder.image
                .setResponseObserver(new LaporanImageView.ResponseObserver() {
                    @Override
                    public void onError() {

                    }

                    @Override
                    public void onSuccess() {

                    }
                });
    } else {
        viewHolder.image.setVisibility(View.GONE);
    }


    viewHolder.itemView.setTag(terbaruItem);
}


@Override
public int getItemCount() {
    return listItems.size();
}
}

当我运行应用程序时出现此错误。

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.company.report/com.company.report.activity.HomeActivity}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
        at android.app.ActivityThread.access$600(ActivityThread.java:123)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4424)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
        at id.co.aascenter.suarawarga.activity.HomeFragment.onCreateView(HomeFragment.java:126)
        at android.support.v4.app.Fragment.performCreateView(Fragment.java:1789)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:955)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1138)
        at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:740)
        at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1501)
        at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:551)
        at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1133)
        at android.app.Activity.performStart(Activity.java:4475)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1929)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
        at android.app.ActivityThread.access$600(ActivityThread.java:123)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4424)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
        at dalvik.system.NativeStart.main(Native Method)

你可以参考我下面的示例代码。我已经测试过。

public class RecycleCardActivityFragment extends Fragment {

    private final List<Person> mPersonList = new ArrayList<>();

    public RecycleCardActivityFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_recycle_card, container, false);

        Context context = getActivity();

        RecyclerView recyclerView = (RecyclerView) view.findViewById(R.id.recycleView);
        recyclerView.setHasFixedSize(true);

        LinearLayoutManager layoutManager = new LinearLayoutManager(context);
        recyclerView.setLayoutManager(layoutManager);

        final RVAdapter rvAdapter = new RVAdapter(mPersonList);
        recyclerView.setAdapter(rvAdapter);

        RequestQueue requestQueue = Volley.newRequestQueue(context);
        String url = "http://192.16.1.100/api/persons";

        JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(url, new Response.Listener<JSONArray>() {
            @Override
            public void onResponse(JSONArray response) {
                try {
                    if (response.length() > 0) {
                        mPersonList.clear();
                        for (int i = 0; i < response.length(); i++) {
                            JSONObject jsonObject = response.getJSONObject(i);
                            Person person = new Person();
                            if (!jsonObject.isNull("name")) {
                                person.name = jsonObject.getString("name");
                            }
                            if (!jsonObject.isNull("age")) {
                                person.age = jsonObject.getInt("age");
                            }
                            mPersonList.add(i, person);
                        }
                        rvAdapter.notifyDataSetChanged();
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Log.e("VOLLEY", error.toString());
            }
        });

        requestQueue.add(jsonArrayRequest);

        return view;
    }
}

有关Person类和RVAdapter同学们，请看我对以下问题的回答

如何使用 volley 将数据（json）加载到回收器视图中

希望这可以帮助！