public class home extends Fragment{

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        //returning our layout file
        //change R.layout.yourlayoutfilename for each of your fragments

        postlist = (ListView)getView().findViewById(R.id.postList);
        progressDialog = new ProgressDialog(getActivity());
        progressDialog.setMessage("Loading...");
        progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        progressDialog.show();

        StringRequest request = new StringRequest(Request.Method.GET, url, new Response.Listener<String>() {
            @Override
            public void onResponse(String s) {
                gson = new Gson();
                list = (List) gson.fromJson(s, List.class);
                postTitle = new String[list.size()];

                for (int i = 0; i < list.size(); ++i) {
                    mapPost = (Map<String, Object>) list.get(i);
                    mapTitle = (Map<String, Object>) mapPost.get("title");
                    postTitle[i] = (String) mapTitle.get("rendered");
                }
                **postlist.setAdapter(new ArrayAdapter(getActivity(),android.R.layout.simple_list_item_1, postTitle));//R is not Resolved**
                progressDialog.dismiss();

            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError volleyerror) {
                Toast.makeText(getActivity(),"Some error occurred", Toast.LENGTH_LONG).show();

            }
        });

        return inflater.inflate(R.layout.home, container, false);
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        //you can set the title for your toolbar here for different fragments different titles
        getActivity().setTitle("Home");
    }
}

出现错误：无法找到符号变量R。如何解决它。相同的代码在活动中运行良好，但在活动中使用时会产生错误。