RecyclerView没有显示任何项目

Question

I have a RecyclerView which items I populate from json response.

public class UserProfile extends AppCompatActivity {

private UserData userData;
private ProfileNewsFeedAdapter adapter;
private ArrayList<ProgramModel> list;
private RecyclerView profileNewsFeed;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.user_profile_activity);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    userData = new UserData(this);
    list = new ArrayList<>();
    adapter = new ProfileNewsFeedAdapter(getActivity(), list);

    initializeViews();
}

private void initializeViews() {

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    toolbar.setTitle(userData.getName());

    TextView userEmail = (TextView) findViewById(R.id.emailPrfId);
    TextView birthday = (TextView) findViewById(R.id.birthdayId);
    TextView userClass = (TextView) findViewById(R.id.userClassId);

    userEmail.setText(userData.getEmail());
    birthday.setText("Ditëlindja: " + userData.getBirthday());
    userClass.setText("Klasa: " + userData.getUserClass());
    setFont(userEmail);
    setFont(birthday);
    setFont(userClass);

    profileNewsFeed = (RecyclerView) findViewById(R.id.profileNewsFeed);
    profileNewsFeed.setLayoutManager(new LinearLayoutManager(this));
    profileNewsFeed.setItemAnimator(new DefaultItemAnimator());
    profileNewsFeed.setHasFixedSize(true);
    profileNewsFeed.setAdapter(adapter);


    GetBorrowedBooks getBorrowedBooks = new GetBorrowedBooks();
    getBorrowedBooks.execute();
}

private void setFont(TextView textView) {
    textView.setTypeface(Typeface.createFromAsset(getAssets(), "fonts/Roboto-Light.ttf"));
}

private AppCompatActivity getActivity() {
    return this;
}


private class GetBorrowedBooks extends AsyncTask<Void, Void, Void> {


    @Override
    protected Void doInBackground(Void... voids) {
        String userId = userData.getUserId();

        StringRequest stringRequest = new StringRequest(Request.Method.GET, "http://ec2-52-39-232-168.us-west-2.compute.amazonaws.com/user/" + userId + "/requests", new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                try {
                    JSONArray jsonArray = new JSONArray(response);

                    if (jsonArray.length() > 0) {
                        for (int i = 0; i < jsonArray.length(); i++) {
                            JSONObject jsonObject = jsonArray.getJSONObject(i);
                            String imageName = "http://ec2-52-39-232-168.us-west-2.compute.amazonaws.com/files/books/" + jsonObject.getString("cover");

                            list.add(new ProgramModel(jsonObject.getString("title"), jsonObject.getString("author"), imageName));
                        }
                    }

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

            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                MyDynamicToast.errorMessage(AppController.getInstance(), "Volley did not respond!");
            }
        });

        AppController.getInstance().addToRequestQueue(stringRequest);

        return null;
    }
}

}

This is the adapter code:

public class ProfileNewsFeedAdapter extends RecyclerView.Adapter<ProfileNewsFeedAdapter.MyViewHolder> {

private AppCompatActivity activity;
private ArrayList<ProgramModel> program;
private LayoutInflater inflater;

public ProfileNewsFeedAdapter(AppCompatActivity activity, ArrayList<ProgramModel> program) {
    this.activity = activity;
    inflater = activity.getLayoutInflater();
    this.program = program;
}

class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
    TextView title, author;
    ImageView bookImage;

    MyViewHolder(View v) {
        super(v);
        title = (TextView) v.findViewById(R.id.bookTitleBorrowId);
        author = (TextView) v.findViewById(R.id.bookAuthorBorrowId);
        bookImage = (ImageView) v.findViewById(R.id.bookImageBorrowCardId);
    }

    void setMenuDetail(ProgramModel model, final int position) {
        title.setText(model.getTitle());
        author.setText(model.getMessage());

        // Set text fonts
        title.setTypeface(Typeface.createFromAsset(activity.getAssets(), "fonts/Roboto-Bold.ttf"));
        author.setTypeface(Typeface.createFromAsset(activity.getAssets(), "fonts/Roboto-Light.ttf"));

        Picasso.with(activity).load(model.getImageUrl()).into(bookImage);

        bookImage.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.bookImageCardId:
                new GetBookInfo(activity, title.getText().toString()).execute();
                break;
        }
    }
}

@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View v = inflater.inflate(R.layout.profile_cardview_item, parent, false);
    return new MyViewHolder(v);
}

@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
    ProgramModel menuModel = program.get(position);
    holder.setMenuDetail(menuModel, position);
}

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

private class GetBookInfo extends AsyncTask<Void, Void, Void> {

    private String bookTitle, bookAuthor, bookDescription, requestedBook, bookUrl, bookId;
    private int copies;
    private Context c;

    GetBookInfo(Context c, String requestedBook) {
        this.c = c;
        this.requestedBook = requestedBook;
    }

    @Override
    protected void onPreExecute() {
    }

    @Override
    protected Void doInBackground(Void... voids) {
        fetchBookInfo();
        return null;
    }

    private void fetchBookInfo() {
        StringRequest stringRequest = new StringRequest(Request.Method.GET, AppConfig.URL_FETCH_BOOKS, 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);
                        if (jsonObject.getString("title").equals(requestedBook)) {
                            bookId = "" + jsonObject.getInt("id");
                            bookTitle = jsonObject.getString("title");
                            bookAuthor = jsonObject.getString("author");
                            bookDescription = jsonObject.getString("description");
                            copies = jsonObject.getInt("quantity");
                            setBookUrl("http://ec2-52-39-232-168.us-west-2.compute.amazonaws.com/files/books/" + jsonObject.getString("cover"));
                            Intent intent = new Intent(c, BookActivity.class);
                            intent.putExtra("title", getBookTitle());
                            intent.putExtra("author", getBookAuthor());
                            intent.putExtra("bookId", getBookId());
                            intent.putExtra("description", getBookDescription());
                            intent.putExtra("copies", getCopies());
                            intent.putExtra("description", getBookDescription());
                            intent.putExtra("bookUrl", getBookUrl());
                            intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                            c.startActivity(intent);
                        }
                    }

                } catch (JSONException e) {
                    e.printStackTrace();
                    Log.e("JSON Error: ", "" + e.getMessage());
                }

            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                MyDynamicToast.errorMessage(AppController.getInstance(), "Volley Error!");
            }
        });

        // Adding request to request queue
        AppController.getInstance().addToRequestQueue(stringRequest);
    }

    String getBookTitle() {
        return bookTitle;
    }

    String getBookAuthor() {
        return bookAuthor;
    }

    String getBookDescription() {
        return bookDescription;
    }

    String getBookId() {
        return bookId;
    }

    int getCopies() {
        return copies;
    }

    private void setBookUrl(String url) {
        bookUrl = url;
    }

    String getBookUrl() {
        return bookUrl;
    }

}

}

This is the ProgramModel class from which I get item's datas:

public class ProgramModel {

private String title;
private String message;
private int image;
private String imageUrl;

public ProgramModel(String title, String message, int image) {
    this.title = title;
    this.message = message;
    this.image = image;
}

public ProgramModel(String title, String message) {
    this.title = title;
    this.message = message;

}

public ProgramModel(String title, String message, String imageUrl) {
    this.title = title;
    this.message = message;
    this.imageUrl = imageUrl;

}

public String getTitle() {
    return title;
}

public void setTitle(String title) {
    this.title = title;
}

public String getMessage() {
    return message;
}

int getImage() {
    return image;
}

public void setImage(int image) {
    this.image = image;
}

public String getImageUrl() {
    return this.imageUrl;
}
}

This is the main layout code:

 <?xml version="1.0" encoding="utf-8"?> <android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@color/white" android:fitsSystemWindows="true" tools:context="com.libraryhf.libraryharryfultz.activity.UserProfile"> <android.support.design.widget.AppBarLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:theme="@style/AppTheme.AppBarOverlay"> <android.support.v7.widget.Toolbar android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="?attr/actionBarSize" android:background="?attr/colorPrimary" app:popupTheme="@style/AppTheme.PopupOverlay" /> </android.support.design.widget.AppBarLayout> <android.support.v4.widget.NestedScrollView xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" app:layout_behavior="@string/appbar_scrolling_view_behavior"> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="horizontal" android:weightSum="4"> <android.support.v7.widget.AppCompatImageView android:id="@+id/userImageId" android:layout_width="0dp" android:layout_height="80dp" android:layout_marginTop="3dp" android:layout_weight="1" android:src="@drawable/prf_image" /> <LinearLayout android:layout_width="0dp" android:layout_height="wrap_content" android:layout_marginTop="3dp" android:layout_weight="3" android:orientation="vertical" android:padding="7dp"> <android.support.v7.widget.AppCompatTextView android:id="@+id/emailPrfId" android:layout_width="wrap_content" android:layout_height="wrap_content" /> <android.support.v7.widget.AppCompatTextView android:id="@+id/birthdayId" android:layout_width="match_parent" android:layout_height="wrap_content" android:background="?attr/selectableItemBackground" android:clickable="true" android:paddingTop="7dp" /> <android.support.v7.widget.AppCompatTextView android:id="@+id/userClassId" android:layout_width="match_parent" android:layout_height="wrap_content" android:background="?attr/selectableItemBackground" android:clickable="true" android:paddingTop="7dp" /> </LinearLayout> </LinearLayout> </android.support.v4.widget.NestedScrollView> <android.support.v7.widget.RecyclerView android:id="@+id/profileNewsFeed" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_marginTop="150dp" android:scrollbars="none" /> </android.support.design.widget.CoordinatorLayout> 

This is the single item layout:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/colorAccent">

    <android.support.v7.widget.CardView xmlns:card_view="http://schemas.android.com/apk/res-auto"
        android:id="@+id/item_cardView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        card_view:cardBackgroundColor="@color/colorAccent"
        card_view:cardCornerRadius="4dp"
        card_view:cardElevation="5dp"
        card_view:contentPadding="7dp">

        <android.support.v7.widget.LinearLayoutCompat
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <TextView
                android:id="@+id/bookTitleBorrowId"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="start"
                android:layout_margin="5dp"
                android:text="@string/dummyText"
                android:textColor="@color/white"
                android:textSize="20sp" />


            <android.support.v7.widget.LinearLayoutCompat
                android:layout_width="wrap_content"
                android:layout_height="0dp"
                android:layout_marginStart="9dp"
                android:layout_weight="7"
                android:orientation="horizontal">

                <android.support.v7.widget.AppCompatImageView
                    android:layout_width="16dp"
                    android:layout_height="16dp"
                    android:layout_marginTop="1dp"
                    android:layout_weight="1"
                    app:srcCompat="@drawable/writer_icon" />

                <TextView
                    android:id="@+id/bookAuthorBorrowId"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginStart="10dp"
                    android:layout_weight="6"
                    android:text="@string/dummyText"
                    android:textColor="@color/white"
                    android:textSize="13sp" />

            </android.support.v7.widget.LinearLayoutCompat>


            <ImageView
                android:id="@+id/bookImageBorrowCardId"
                android:layout_width="match_parent"
                android:layout_height="200dp"
                android:layout_centerHorizontal="true"
                android:layout_marginBottom="10dp"
                tools:ignore="ContentDescription" />

        </android.support.v7.widget.LinearLayoutCompat>




     </android.support.v7.widget.CardView>
    </LinearLayout>

Unfortunately my items are not showing on the screen. I know that recyclerview is shown because I can notice the animations on top and on bottom but the items are not there. Where have I gone wrong here? Thank you.

Answer 1

you are accessing views from doInBackground, doInBackground is called on a different thread. you should access those views from onPostExecute(), an AsyncTask method that is called on the ui thread.

Answer 2

Try adding adapter.notifyDataSetChanged(); after you add new element to the list. If you don't notify the adapter that the list changed, it won't update the recyclerview so that the data is always the empty list that is declared at the start.