Question

当我刷新SwipeRefreshLayout时，我试图在我的布局中设置一些视图。但是，当我试图拨打NullPointerException时，我会继续findViewById。我的代码：

public class LecturerFragment extends Fragment
    implements SwipeRefreshLayout.OnRefreshListener {

    private SwipeRefreshLayout swipeRefreshLayout;
    private View rootView;


    private OnFragmentInteractionListener mListener;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        rootView = inflater.inflate(R.layout.fragment_lecturer, container, false);


        return rootView;
    }


    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {

        if (savedInstanceState == null) {
            swipeRefreshLayout = (SwipeRefreshLayout) rootView.findViewById(R.id.swipe_refresh_lecturer);
            swipeRefreshLayout.post(new Runnable() {
                @Override
                public void run() {
                    swipeRefreshLayout.setRefreshing(true);
                }
            });
            swipeRefreshLayout.setColorSchemeResources(R.color.refresh_1, R.color.refresh_2, R.color.refresh_3, R.color.refresh_4);
            swipeRefreshLayout.setOnRefreshListener(this);

            this.setLecturers();
        }
    }



    private void setLecturers() {
        String apiUrl = this.getResources().getString(R.string.api_url);

        RestAdapter restAdapter = new RestAdapter.Builder().setEndpoint(apiUrl).build();

        LecturerApi api = restAdapter.create(LecturerApi.class);

        api.getLecturers(new Callback<ArrayList<LecturerModel>>() {
            @Override
            public void success(ArrayList<LecturerModel> lecturerModels, Response response) {
                //some setter code

                swipeRefreshLayout = (SwipeRefreshLayout) getView().findViewById(R.id.swipe_refresh_lecturer);
                swipeRefreshLayout.setRefreshing(false);
            }

            @Override
            public void failure(RetrofitError error) {
                Toast.makeText(getActivity(), "Failed to fetch lecturers data", Toast.LENGTH_LONG).show();

                swipeRefreshLayout = (SwipeRefreshLayout) getView().findViewById(R.id.swipe_refresh_lecturer);
                swipeRefreshLayout.setRefreshing(false);
            }
        });

    }

    @Override
    public void onRefresh() {
        this.setLecturers();
    }
}

每次调用findViewById方法时，我都会收到错误。

Answer 1

使用您正在膨胀的视图（rootView）作为参考，而不是getView()。

使用

swipeRefreshLayout = (SwipeRefreshLayout) rootView.findViewById(R.id.swipe_refresh_lecturer);

而不是

swipeRefreshLayout = (SwipeRefreshLayout) getView().findViewById(R.id.swipe_refresh_lecturer);

Answer 2

仅指定swipeRefreshLayout一次：创建片段视图时：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    rootView = inflater.inflate(R.layout.fragment_lecturer, container, false);
    swipeRefreshLayout = rootView.findViewById(R.id.swipe_refresh_lecturer);

    return rootView;
}

从代码中删除所有其他findViewByIds。

用片段调用onRefresh中的findViewById

2 个答案: