Fragment，RecyclerView：没有附加适配器；跳过布局

Question

我正在使用 Fragment 来查看 RecyclerView。但我总是得到这个错误

E/RecyclerView：没有附加适配器；跳过布局

我为我的 recyclerview 创建了一个适配器，但布局没有显示。 php后端工作正常。有人可以帮忙吗？这是我的片段和适配器代码

Tips.java

public class Tips extends Fragment {

Configuration config = new Configuration();
String HttpUrl = config.viewtips_url;
List<TipModel> tipList;
RecyclerView recyclerView;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.fragment_tips, container, false);
    recyclerView = view.findViewById(R.id.recyclerView);
    recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
    tipList = new ArrayList<>();
    loadTips();
    return view;
}

private void loadTips() {
    StringRequest stringRequest = new StringRequest(Request.Method.GET, HttpUrl,
            new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    try {
                        JSONArray jsonArray = new JSONArray(response);
                        for (int i = 0; i < jsonArray.length(); i++) {
                            JSONObject jsonObject = jsonArray.getJSONObject(i);
                            tipList.add(new TipModel(
                                    jsonObject.getInt("id"),
                            jsonObject.getString("tip")

                            ));
                        }
                        TipAdapter tipAdapter = new TipAdapter(getActivity(), tipList);
                        recyclerView.setAdapter(tipAdapter);
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {

                }
            });
    Volley.newRequestQueue(getActivity()).add(stringRequest);
}

TipAdapter.java

public class TipAdapter extends RecyclerView.Adapter<TipAdapter.TipViewHolder> {

private Context context;
private List<TipModel> tipList;

public TipAdapter(Context context, List<TipModel> tipList) {
    this.context = context;
    this.tipList = tipList;
}

@Override
public TipViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    LayoutInflater inflater = LayoutInflater.from(context);
    View view = inflater.inflate(R.layout.itemlayout, null);
    return new TipViewHolder(view);
}

@Override
public void onBindViewHolder(TipViewHolder holder, int position) {
    TipModel tipModel = tipList.get(position);


    holder.textViewTip.setText(tipModel.getTip());

}

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

class TipViewHolder extends RecyclerView.ViewHolder {
    TextView textViewTip;

    public TipViewHolder(View view) {
        super(view);
        textViewTip = view.findViewById(R.id.textViewTip);
    }
}

Answer 1

这是因为RecyclerView在创建视图时调度布局时需要一个适配器，所以如果创建视图时没有适配器也没关系，它会跳过布局部分。

如果您担心错误，那么您可以在创建视图时设置一个空适配器：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    return inflater.inflate(R.layout.fragment_tips, container, false);
}

@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
    recyclerView = view.findViewById(R.id.recyclerView);
    recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
    tipList = new ArrayList<>();
    recyclerView.setAdapter(new TipAdapter(getActivity(), tipList));
}

然后在响应回调中调整你的代码：

@Override
public void onResponse(String response) {

    // Instead of setting adapter here...
    // TipAdapter tipAdapter = new TipAdapter(getActivity(), tipList);
    // recyclerView.setAdapter(tipAdapter);

    // Just notify the adapter that tipList has changed.
    recyclerView.getAdapter().notifyDataSetChanged();

    // ...
}

Answer 2

TipList是Adapter的datastore，属于Adapter，不属于Fragment

我已经编辑了你的代码（无权访问 Android Studio，在文本编辑器中进行，请检查语法错误）

片段

public class Tips extends Fragment {

Configuration config = new Configuration();
String HttpUrl = config.viewtips_url;

RecyclerView recyclerView;
TipAdapter tipAdapter;

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

    // Initialize the Tip Adapter
    tipAdapter = new TipAdapter(getActivity());

    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.fragment_tips, container, false);
    recyclerView = view.findViewById(R.id.recyclerView);
    recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
    // Assign the Adapter to recyclerView
    recyclerView.setAdapter(tipAdapter);
    
    return view;
}

private void loadTips() {
    StringRequest stringRequest = new StringRequest(Request.Method.GET, HttpUrl,
            new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    try {
                        JSONArray jsonArray = new JSONArray(response);
                        // Create a new TipList
                        List<TipModel> tipList = new ArrayList<>();
                        
                        for (int i = 0; i < jsonArray.length(); i++) {
                            
                            JSONObject jsonObject = jsonArray.getJSONObject(i);
                            tipList.add(new TipModel(
                                jsonObject.getInt("id"),
                                jsonObject.getString("tip")
                            ));
                        }
                        
                        tipAdapter.updateWith(tipList)
                        
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {

                }
            });
    Volley.newRequestQueue(getActivity()).add(stringRequest);
}

提示适配器

public class TipAdapter extends RecyclerView.Adapter<TipAdapter.TipViewHolder> {

private Context context;
private List<TipModel> tipList = new ArrayList<>();

public TipAdapter(Context context) {
    this.context = context;
}

@Override
public TipViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    LayoutInflater inflater = LayoutInflater.from(context);
    View view = inflater.inflate(R.layout.itemlayout, null);
    return new TipViewHolder(view);
}

@Override
public void onBindViewHolder(TipViewHolder holder, int position) {
    TipModel tipModel = tipList.get(position);


    holder.textViewTip.setText(tipModel.getTip());

}

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

class TipViewHolder extends RecyclerView.ViewHolder {
    TextView textViewTip;

    public TipViewHolder(View view) {
        super(view);
        textViewTip = view.findViewById(R.id.textViewTip);
    }
}

public updateWith(List<TipModel> tipList) {
    this.tipList = tipList;
    notifyDataSetChanged();
}

Answer 3

当我在片段中膨胀回收站视图时遇到类似问题时，我就是这样做的。这段代码非常适合我：

附： - 这是我在应用程序中使用的代码补丁。给您带来的不便，我深表歉意。

首先，在 Display Fragment 的 onCreateView() 中：

public View onCreateView(@NonNull LayoutInflater inflater,
                             ViewGroup container, Bundle savedInstanceState) {
        View root = inflater.inflate(R.layout.fragment_home, container, false);
        Firebase.setAndroidContext(getActivity());
        ((Home_Drawer) getActivity())
                .setActionBarTitle("Home");

        recyclerView = (RecyclerView) root.findViewById(R.id.recycler_view_home_frag);
        progressBar = (ProgressBar) root.findViewById(R.id.mainPageProgressBar);

//        Log.i("inside", "rv initiated" +mLayoutManager.toString());
        // Assign activity this to progress dialog.
        progressDialog = new ProgressDialog(getActivity());

        // Setting up message in Progress dialog.
        progressDialog.setMessage("Loading Images From Firebase.");
        // Showing progress dialog.
        progressDialog.show();
        // The path is already defined in MainActivity.
        databaseReference = FirebaseDatabase.getInstance().getReference().child("productDisplay");
        Log.i("inside", databaseReference.toString());

        return root;
    }

然后，我们调用 onStart()。这是因为回收器视图通常不会膨胀，在 onCreateView() 中设置适配器。

@Override
    public void onStart() {
        super.onStart();

        FirebaseRecyclerOptions<DisplayItemsModel> item_info =
                new FirebaseRecyclerOptions.Builder<DisplayItemsModel>()
                        .setQuery(databaseReference, DisplayItemsModel.class)
                        .build();
        final FirebaseRecyclerAdapter<DisplayItemsModel, ViewHolder> info_adapter =
                new FirebaseRecyclerAdapter<DisplayItemsModel, ViewHolder>(item_info) {
                    @Override
                    protected void onBindViewHolder(final ViewHolder holder, final int position, final DisplayItemsModel model) {
                        mContext = getContext();
                        final DatabaseReference dref = getRef(position).getRef();
                        Log.i("dref", dref.toString());
                        // Adding Add Value Event Listener to databaseReference.
                        dref.addValueEventListener(new ValueEventListener() {
                            @Override
                            public void onDataChange(final DataSnapshot snapshot) {

                                holder.item_name_single_card.setText(snapshot.child("name").getValue().toString());
                                holder.price_single_card.setText(snapshot.child("price").getValue().toString());
                                String image_url = snapshot.child("image").getValue().toString();

                                Picasso.get().load(image_url).into(holder.thumbnail);
                        // Continue with your code.

这对我来说非常有效。希望它能解决你的问题。