Add a ViewPager in ViewUserDetailActivity to display comments. Fixed searching posts without specifying subreddit will result in no posts. Use another api endpoint for fetching posts in ViewUserDetailActivity.

app/src/main/java/ml/docilealligator/infinityforreddit/AppComponent.java

@@ -24,4 +24,5 @@ interface AppComponent {
     void inject(PostVideoActivity postVideoActivity);
     void inject(FlairBottomSheetFragment flairBottomSheetFragment);
     void inject(RulesActivity rulesActivity);
+    void inject(CommentsListingFragment commentsListingFragment);
 }

app/src/main/java/ml/docilealligator/infinityforreddit/CommentAndPostRecyclerViewAdapter.java

@@ -442,7 +442,7 @@ class CommentAndPostRecyclerViewAdapter extends RecyclerView.Adapter<RecyclerVie
                 ((LoadMoreChildCommentsViewHolder) holder).placeholderTextView.setText(R.string.comment_load_more_comments);
             }
         } else if(holder instanceof LoadMoreCommentsFailedViewHolder) {
-            ((LoadMoreCommentsFailedViewHolder) holder).errorTextView.setText(R.string.post_load_comments_failed);
+            ((LoadMoreCommentsFailedViewHolder) holder).errorTextView.setText(R.string.load_comments_failed);
         }
     }
 

app/src/main/java/ml/docilealligator/infinityforreddit/CommentDataSource.java

@@ -0,0 +1,200 @@
+package ml.docilealligator.infinityforreddit;
+
+import android.os.AsyncTask;
+import android.util.Log;
+
+import androidx.annotation.NonNull;
+import androidx.lifecycle.MutableLiveData;
+import androidx.paging.PageKeyedDataSource;
+
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
+
+import java.util.ArrayList;
+import java.util.Locale;
+
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+import retrofit2.Retrofit;
+
+public class CommentDataSource extends PageKeyedDataSource<String, CommentData> {
+    interface OnCommentFetchedCallback {
+        void hasComment();
+        void noComment();
+    }
+
+    private Retrofit retrofit;
+    private Locale locale;
+    private String username;
+    private OnCommentFetchedCallback onCommentFetchedCallback;
+
+    private MutableLiveData<NetworkState> paginationNetworkStateLiveData;
+    private MutableLiveData<NetworkState> initialLoadStateLiveData;
+
+    private LoadInitialParams<String> initialParams;
+    private LoadInitialCallback<String, CommentData> initialCallback;
+    private LoadParams<String> params;
+    private LoadCallback<String, CommentData> callback;
+
+    CommentDataSource(Retrofit retrofit, Locale locale, String username, OnCommentFetchedCallback onCommentFetchedCallback) {
+        this.retrofit = retrofit;
+        this.locale = locale;
+        this.username = username;
+        paginationNetworkStateLiveData = new MutableLiveData();
+        initialLoadStateLiveData = new MutableLiveData();
+        this.onCommentFetchedCallback = onCommentFetchedCallback;
+    }
+
+    MutableLiveData getPaginationNetworkStateLiveData() {
+        return paginationNetworkStateLiveData;
+    }
+
+    MutableLiveData getInitialLoadStateLiveData() {
+        return initialLoadStateLiveData;
+    }
+
+    void retry() {
+        loadInitial(initialParams, initialCallback);
+    }
+
+    void retryLoadingMore() {
+        loadAfter(params, callback);
+    }
+
+    @Override
+    public void loadInitial(@NonNull LoadInitialParams<String> params, @NonNull LoadInitialCallback<String, CommentData> callback) {
+        initialParams = params;
+        initialCallback = callback;
+
+        RedditAPI api = retrofit.create(RedditAPI.class);
+        Call<String> bestPost = api.getUserComments(username, null);
+        bestPost.enqueue(new Callback<String>() {
+            @Override
+            public void onResponse(@NonNull Call<String> call, @NonNull Response<String> response) {
+                if(response.isSuccessful()) {
+                    new ParseCommentAsyncTask(response.body(), locale, new ParseCommentAsyncTask.ParseCommentAsyncTaskListener() {
+                        @Override
+                        public void parseSuccessful(ArrayList<CommentData> comments, String after) {
+                            if(comments.size() == 0) {
+                                onCommentFetchedCallback.noComment();
+                            } else {
+                                onCommentFetchedCallback.hasComment();
+                            }
+
+                            callback.onResult(comments, null, after);
+                            initialLoadStateLiveData.postValue(NetworkState.LOADED);
+                        }
+
+                        @Override
+                        public void parseFailed() {
+                            Log.i("Comments fetch error", "Error parsing data");
+                            initialLoadStateLiveData.postValue(new NetworkState(NetworkState.Status.FAILED, "Error parsing data"));
+                        }
+                    }).execute();
+                } else {
+                    Log.i("Comments fetch error", "Error parsing data");
+                    initialLoadStateLiveData.postValue(new NetworkState(NetworkState.Status.FAILED, "Error parsing data"));
+                }
+            }
+
+            @Override
+            public void onFailure(@NonNull Call<String> call, @NonNull Throwable t) {
+                Log.i("Comments fetch error", "Error parsing data");
+                initialLoadStateLiveData.postValue(new NetworkState(NetworkState.Status.FAILED, "Error parsing data"));
+            }
+        });
+    }
+
+    @Override
+    public void loadBefore(@NonNull LoadParams<String> params, @NonNull LoadCallback<String, CommentData> callback) {
+
+    }
+
+    @Override
+    public void loadAfter(@NonNull LoadParams<String> params, @NonNull LoadCallback<String, CommentData> callback) {
+        this.params = params;
+        this.callback = callback;
+
+        RedditAPI api = retrofit.create(RedditAPI.class);
+        Call<String> bestPost = api.getUserComments(username, params.key);
+        bestPost.enqueue(new Callback<String>() {
+            @Override
+            public void onResponse(@NonNull Call<String> call, @NonNull Response<String> response) {
+                if(response.isSuccessful()) {
+                    new ParseCommentAsyncTask(response.body(), locale, new ParseCommentAsyncTask.ParseCommentAsyncTaskListener() {
+                        @Override
+                        public void parseSuccessful(ArrayList<CommentData> comments, String after) {
+                            if(after == null || after.equals("") || after.equals("null")) {
+                                callback.onResult(comments, null);
+                            } else {
+                                callback.onResult(comments, after);
+                            }
+                            paginationNetworkStateLiveData.postValue(NetworkState.LOADED);
+                        }
+
+                        @Override
+                        public void parseFailed() {
+                            Log.i("Comments fetch error", "Error parsing data");
+                            paginationNetworkStateLiveData.postValue(new NetworkState(NetworkState.Status.FAILED, "Error parsing data"));
+                        }
+                    }).execute();
+                } else {
+                    paginationNetworkStateLiveData.postValue(new NetworkState(NetworkState.Status.FAILED, "Error parsing data"));
+                }
+            }
+
+            @Override
+            public void onFailure(@NonNull Call<String> call, @NonNull Throwable t) {
+                paginationNetworkStateLiveData.postValue(new NetworkState(NetworkState.Status.FAILED, "Error parsing data"));
+            }
+        });
+    }
+
+    private static class ParseCommentAsyncTask extends AsyncTask<Void, ArrayList<CommentData>, ArrayList<CommentData>> {
+        private String response;
+        private String after;
+        private Locale locale;
+        private ParseCommentAsyncTaskListener parseCommentAsyncTaskListener;
+
+        interface ParseCommentAsyncTaskListener {
+            void parseSuccessful(ArrayList<CommentData> comments, String after);
+            void parseFailed();
+        }
+
+        ParseCommentAsyncTask(String response, Locale locale, ParseCommentAsyncTaskListener parseCommentAsyncTaskListener) {
+            this.response = response;
+            this.locale = locale;
+            this.parseCommentAsyncTaskListener = parseCommentAsyncTaskListener;
+        }
+
+        @Override
+        protected ArrayList<CommentData> doInBackground(Void... voids) {
+            try {
+                JSONObject data = new JSONObject(response).getJSONObject(JSONUtils.DATA_KEY);
+                JSONArray commentsJSONArray = data.getJSONArray(JSONUtils.CHILDREN_KEY);
+                ArrayList<CommentData> comments = new ArrayList<>();
+                for(int i = 0; i < commentsJSONArray.length(); i++) {
+                    JSONObject commentJSON = commentsJSONArray.getJSONObject(i).getJSONObject(JSONUtils.DATA_KEY);
+                    comments.add(ParseComment.parseSingleComment(commentJSON, 0, locale));
+                }
+                after = data.getString(JSONUtils.AFTER_KEY);
+                return comments;
+            } catch (JSONException e) {
+                e.printStackTrace();
+            }
+            return null;
+        }
+
+        @Override
+        protected void onPostExecute(ArrayList<CommentData> commentData) {
+            super.onPostExecute(commentData);
+            if(commentData != null) {
+                parseCommentAsyncTaskListener.parseSuccessful(commentData, after);
+            } else {
+                parseCommentAsyncTaskListener.parseFailed();
+            }
+        }
+    }
+}

app/src/main/java/ml/docilealligator/infinityforreddit/CommentDataSourceFactory.java

@@ -0,0 +1,43 @@
+package ml.docilealligator.infinityforreddit;
+
+import androidx.annotation.NonNull;
+import androidx.lifecycle.MutableLiveData;
+import androidx.paging.DataSource;
+
+import java.util.Locale;
+
+import retrofit2.Retrofit;
+
+class CommentDataSourceFactory extends DataSource.Factory {
+    private Retrofit retrofit;
+    private Locale locale;
+    private String username;
+    private CommentDataSource.OnCommentFetchedCallback onCommentFetchedCallback;
+
+    private CommentDataSource commentDataSource;
+    private MutableLiveData<CommentDataSource> commentDataSourceLiveData;
+
+    CommentDataSourceFactory(Retrofit retrofit, Locale locale, String username, CommentDataSource.OnCommentFetchedCallback onCommentFetchedCallback) {
+        this.retrofit = retrofit;
+        this.locale = locale;
+        this.username = username;
+        commentDataSourceLiveData = new MutableLiveData<>();
+        this.onCommentFetchedCallback = onCommentFetchedCallback;
+    }
+
+    @NonNull
+    @Override
+    public DataSource create() {
+        commentDataSource = new CommentDataSource(retrofit, locale, username, onCommentFetchedCallback);
+        commentDataSourceLiveData.postValue(commentDataSource);
+        return commentDataSource;
+    }
+
+    public MutableLiveData<CommentDataSource> getCommentDataSourceLiveData() {
+        return commentDataSourceLiveData;
+    }
+
+    CommentDataSource getCommentDataSource() {
+        return commentDataSource;
+    }
+}

app/src/main/java/ml/docilealligator/infinityforreddit/CommentViewModel.java

@@ -0,0 +1,83 @@
+package ml.docilealligator.infinityforreddit;
+
+import androidx.annotation.NonNull;
+import androidx.arch.core.util.Function;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.Transformations;
+import androidx.lifecycle.ViewModel;
+import androidx.lifecycle.ViewModelProvider;
+import androidx.paging.LivePagedListBuilder;
+import androidx.paging.PagedList;
+
+import java.util.Locale;
+
+import retrofit2.Retrofit;
+
+public class CommentViewModel extends ViewModel {
+    private CommentDataSourceFactory commentDataSourceFactory;
+    private LiveData<NetworkState> paginationNetworkState;
+    private LiveData<NetworkState> initialLoadingState;
+    private LiveData<PagedList<CommentData>> comments;
+
+    public CommentViewModel(Retrofit retrofit, Locale locale, String username,
+                         CommentDataSource.OnCommentFetchedCallback onCommentFetchedCallback) {
+        commentDataSourceFactory = new CommentDataSourceFactory(retrofit, locale, username, onCommentFetchedCallback);
+
+        initialLoadingState = Transformations.switchMap(commentDataSourceFactory.getCommentDataSourceLiveData(),
+                (Function<CommentDataSource, LiveData<NetworkState>>) CommentDataSource::getInitialLoadStateLiveData);
+        paginationNetworkState = Transformations.switchMap(commentDataSourceFactory.getCommentDataSourceLiveData(),
+                (Function<CommentDataSource, LiveData<NetworkState>>) CommentDataSource::getPaginationNetworkStateLiveData);
+        PagedList.Config pagedListConfig =
+                (new PagedList.Config.Builder())
+                        .setEnablePlaceholders(false)
+                        .setPageSize(25)
+                        .build();
+
+        comments = (new LivePagedListBuilder(commentDataSourceFactory, pagedListConfig)).build();
+    }
+
+    LiveData<PagedList<CommentData>> getComments() {
+        return comments;
+    }
+
+    LiveData<NetworkState> getPaginationNetworkState() {
+        return paginationNetworkState;
+    }
+
+    LiveData<NetworkState> getInitialLoadingState() {
+        return initialLoadingState;
+    }
+
+    void refresh() {
+        commentDataSourceFactory.getCommentDataSource().invalidate();
+    }
+
+    void retry() {
+        commentDataSourceFactory.getCommentDataSource().retry();
+    }
+
+    void retryLoadingMore() {
+        commentDataSourceFactory.getCommentDataSource().retryLoadingMore();
+    }
+
+    public static class Factory extends ViewModelProvider.NewInstanceFactory {
+        private Retrofit retrofit;
+        private Locale locale;
+        private String username;
+        private CommentDataSource.OnCommentFetchedCallback onCommentFetchedCallback;
+
+        public Factory(Retrofit retrofit, Locale locale, String username,
+                       CommentDataSource.OnCommentFetchedCallback onCommentFetchedCallback) {
+            this.retrofit = retrofit;
+            this.locale = locale;
+            this.username = username;
+            this.onCommentFetchedCallback = onCommentFetchedCallback;
+        }
+
+        @NonNull
+        @Override
+        public <T extends ViewModel> T create(@NonNull Class<T> modelClass) {
+            return (T) new CommentViewModel(retrofit, locale, username, onCommentFetchedCallback);
+        }
+    }
+}

app/src/main/java/ml/docilealligator/infinityforreddit/CommentsListingFragment.java

@@ -0,0 +1,149 @@
+package ml.docilealligator.infinityforreddit;
+
+
+import android.app.Activity;
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.os.Bundle;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.ImageView;
+import android.widget.LinearLayout;
+import android.widget.TextView;
+
+import androidx.annotation.NonNull;
+import androidx.coordinatorlayout.widget.CoordinatorLayout;
+import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProviders;
+import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
+
+import com.bumptech.glide.Glide;
+import com.bumptech.glide.RequestManager;
+import com.lsjwzh.widget.materialloadingprogressbar.CircleProgressBar;
+
+import javax.inject.Inject;
+import javax.inject.Named;
+
+import butterknife.BindView;
+import butterknife.ButterKnife;
+import retrofit2.Retrofit;
+
+
+/**
+ * A simple {@link Fragment} subclass.
+ */
+public class CommentsListingFragment extends Fragment implements FragmentCommunicator {
+
+    static final String EXTRA_USERNAME_KEY = "ENK";
+
+    @BindView(R.id.coordinator_layout_comments_listing_fragment) CoordinatorLayout mCoordinatorLayout;
+    @BindView(R.id.recycler_view_comments_listing_fragment) RecyclerView mCommentRecyclerView;
+    @BindView(R.id.progress_bar_comments_listing_fragment) CircleProgressBar mProgressBar;
+    @BindView(R.id.fetch_comments_info_linear_layout_comments_listing_fragment) LinearLayout mFetchCommentInfoLinearLayout;
+    @BindView(R.id.fetch_comments_info_image_view_comments_listing_fragment) ImageView mFetchCommentInfoImageView;
+    @BindView(R.id.fetch_comments_info_text_view_comments_listing_fragment) TextView mFetchCommentInfoTextView;
+
+    private RequestManager mGlide;
+
+    private Activity activity;
+
+    private CommentsListingRecyclerViewAdapter mAdapter;
+
+    CommentViewModel mCommentViewModel;
+
+    @Inject
+    @Named("no_oauth")
+    Retrofit mRetrofit;
+
+    @Inject @Named("oauth")
+    Retrofit mOauthRetrofit;
+
+    @Inject @Named("auth_info")
+    SharedPreferences mSharedPreferences;
+
+    public CommentsListingFragment() {
+        // Required empty public constructor
+    }
+
+
+    @Override
+    public View onCreateView(LayoutInflater inflater, ViewGroup container,
+                             Bundle savedInstanceState) {
+        View rootView = inflater.inflate(R.layout.fragment_comments_listing, container, false);
+
+        ((Infinity) activity.getApplication()).getmAppComponent().inject(this);
+
+        ButterKnife.bind(this, rootView);
+
+        mGlide = Glide.with(activity);
+
+        mCommentRecyclerView.setLayoutManager(new LinearLayoutManager(activity));
+
+        CommentViewModel.Factory factory;
+        mAdapter = new CommentsListingRecyclerViewAdapter(activity, mOauthRetrofit,
+                mSharedPreferences, () -> mCommentViewModel.retryLoadingMore());
+
+        String username = getArguments().getString(EXTRA_USERNAME_KEY);
+
+        factory = new CommentViewModel.Factory(mRetrofit, getResources().getConfiguration().locale,
+                username, new CommentDataSource.OnCommentFetchedCallback() {
+            @Override
+            public void hasComment() {
+                mFetchCommentInfoLinearLayout.setVisibility(View.GONE);
+            }
+
+            @Override
+            public void noComment() {
+                mFetchCommentInfoLinearLayout.setOnClickListener(view -> {
+                    //Do nothing
+                });
+                showErrorView(R.string.no_posts);
+            }
+        });
+
+        mCommentRecyclerView.setAdapter(mAdapter);
+
+        mCommentViewModel = ViewModelProviders.of(this, factory).get(CommentViewModel.class);
+        mCommentViewModel.getComments().observe(this, comments -> mAdapter.submitList(comments));
+
+        mCommentViewModel.getInitialLoadingState().observe(this, networkState -> {
+            if(networkState.getStatus().equals(NetworkState.Status.SUCCESS)) {
+                mProgressBar.setVisibility(View.GONE);
+            } else if(networkState.getStatus().equals(NetworkState.Status.FAILED)) {
+                mFetchCommentInfoLinearLayout.setOnClickListener(view -> mCommentViewModel.retry());
+                showErrorView(R.string.load_posts_error);
+            } else {
+                mFetchCommentInfoLinearLayout.setVisibility(View.GONE);
+                mProgressBar.setVisibility(View.VISIBLE);
+            }
+        });
+
+        mCommentViewModel.getPaginationNetworkState().observe(this, networkState -> {
+            mAdapter.setNetworkState(networkState);
+        });
+
+        return rootView;
+    }
+
+    @Override
+    public void onAttach(@NonNull Context context) {
+        super.onAttach(context);
+        this.activity = (Activity) context;
+    }
+
+    @Override
+    public void refresh() {
+        mCommentViewModel.refresh();
+    }
+
+    private void showErrorView(int stringResId) {
+        mProgressBar.setVisibility(View.GONE);
+        if(activity != null && isAdded()) {
+            mFetchCommentInfoLinearLayout.setVisibility(View.VISIBLE);
+            mFetchCommentInfoTextView.setText(stringResId);
+            mGlide.load(R.drawable.load_post_error_indicator).into(mFetchCommentInfoImageView);
+        }
+    }
+}

app/src/main/java/ml/docilealligator/infinityforreddit/CommentsListingRecyclerViewAdapter.java

@@ -0,0 +1,284 @@
+package ml.docilealligator.infinityforreddit;
+
+import android.content.Context;
+import android.content.Intent;
+import android.content.SharedPreferences;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+import android.widget.ImageView;
+import android.widget.RelativeLayout;
+import android.widget.TextView;
+
+import androidx.annotation.NonNull;
+import androidx.cardview.widget.CardView;
+import androidx.core.content.ContextCompat;
+import androidx.paging.PagedListAdapter;
+import androidx.recyclerview.widget.DiffUtil;
+import androidx.recyclerview.widget.RecyclerView;
+
+import CustomView.CustomMarkwonView;
+import butterknife.BindView;
+import butterknife.ButterKnife;
+import retrofit2.Retrofit;
+
+class CommentsListingRecyclerViewAdapter extends PagedListAdapter<CommentData, RecyclerView.ViewHolder> {
+    private Context mContext;
+    private Retrofit mOauthRetrofit;
+    private SharedPreferences mSharedPreferences;
+
+    private static final int VIEW_TYPE_DATA = 0;
+    private static final int VIEW_TYPE_ERROR = 1;
+    private static final int VIEW_TYPE_LOADING = 2;
+
+    private NetworkState networkState;
+    private RetryLoadingMoreCallback mRetryLoadingMoreCallback;
+
+    interface RetryLoadingMoreCallback {
+        void retryLoadingMore();
+    }
+
+    protected CommentsListingRecyclerViewAdapter(Context context, Retrofit oauthRetrofit, SharedPreferences sharedPreferences,
+                                                 RetryLoadingMoreCallback retryLoadingMoreCallback) {
+        super(DIFF_CALLBACK);
+        mContext = context;
+        mOauthRetrofit = oauthRetrofit;
+        mSharedPreferences = sharedPreferences;
+        mRetryLoadingMoreCallback = retryLoadingMoreCallback;
+    }
+
+    private static final DiffUtil.ItemCallback<CommentData> DIFF_CALLBACK = new DiffUtil.ItemCallback<CommentData>() {
+        @Override
+        public boolean areItemsTheSame(@NonNull CommentData CommentData, @NonNull CommentData t1) {
+            return CommentData.getId().equals(t1.getId());
+        }
+
+        @Override
+        public boolean areContentsTheSame(@NonNull CommentData CommentData, @NonNull CommentData t1) {
+            return CommentData.getCommentContent().equals(t1.getCommentContent());
+        }
+    };
+
+    @NonNull
+    @Override
+    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
+        if(viewType == VIEW_TYPE_DATA) {
+            CardView cardView = (CardView) LayoutInflater.from(parent.getContext()).inflate(R.layout.item_comment, parent, false);
+            return new DataViewHolder(cardView);
+        } else if(viewType == VIEW_TYPE_ERROR) {
+            RelativeLayout relativeLayout = (RelativeLayout) LayoutInflater.from(parent.getContext()).inflate(R.layout.item_footer_error, parent, false);
+            return new ErrorViewHolder(relativeLayout);
+        } else {
+            RelativeLayout relativeLayout = (RelativeLayout) LayoutInflater.from(parent.getContext()).inflate(R.layout.item_footer_loading, parent, false);
+            return new LoadingViewHolder(relativeLayout);
+        }
+    }
+
+    @Override
+    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
+        if(holder instanceof DataViewHolder) {
+            CommentData comment = getItem(holder.getAdapterPosition());
+
+            String authorPrefixed = "u/" + comment.getAuthor();
+            ((DataViewHolder) holder).authorTextView.setText(authorPrefixed);
+
+            ((DataViewHolder) holder).commentTimeTextView.setText(comment.getCommentTime());
+
+            ((DataViewHolder) holder).commentMarkdownView.setMarkdown(comment.getCommentContent(), mContext);
+            ((DataViewHolder) holder).scoreTextView.setText(Integer.toString(comment.getScore()));
+
+            switch (comment.getVoteType()) {
+                case 1:
+                    ((DataViewHolder) holder).upvoteButton
+                            .setColorFilter(ContextCompat.getColor(mContext, R.color.colorPrimary), android.graphics.PorterDuff.Mode.SRC_IN);
+                    break;
+                case 2:
+                    ((DataViewHolder) holder).downvoteButton
+                            .setColorFilter(ContextCompat.getColor(mContext, R.color.minusButtonColor), android.graphics.PorterDuff.Mode.SRC_IN);
+                    break;
+            }
+        }
+    }
+
+    @Override
+    public int getItemViewType(int position) {
+        // Reached at the end
+        if (hasExtraRow() && position == getItemCount() - 1) {
+            if (networkState.getStatus() == NetworkState.Status.LOADING) {
+                return VIEW_TYPE_LOADING;
+            } else {
+                return VIEW_TYPE_ERROR;
+            }
+        } else {
+            return VIEW_TYPE_DATA;
+        }
+    }
+
+    @Override
+    public int getItemCount() {
+        if(hasExtraRow()) {
+            return super.getItemCount() + 1;
+        }
+        return super.getItemCount();
+    }
+
+    private boolean hasExtraRow() {
+        return networkState != null && networkState.getStatus() != NetworkState.Status.SUCCESS;
+    }
+
+    void setNetworkState(NetworkState newNetworkState) {
+        NetworkState previousState = this.networkState;
+        boolean previousExtraRow = hasExtraRow();
+        this.networkState = newNetworkState;
+        boolean newExtraRow = hasExtraRow();
+        if (previousExtraRow != newExtraRow) {
+            if (previousExtraRow) {
+                notifyItemRemoved(super.getItemCount());
+            } else {
+                notifyItemInserted(super.getItemCount());
+            }
+        } else if (newExtraRow && !previousState.equals(newNetworkState)) {
+            notifyItemChanged(getItemCount() - 1);
+        }
+    }
+
+    class DataViewHolder extends RecyclerView.ViewHolder {
+        @BindView(R.id.vertical_block_item_post_comment) View verticalBlock;
+        @BindView(R.id.author_text_view_item_post_comment) TextView authorTextView;
+        @BindView(R.id.comment_time_text_view_item_post_comment) TextView commentTimeTextView;
+        @BindView(R.id.comment_markdown_view_item_post_comment) CustomMarkwonView commentMarkdownView;
+        @BindView(R.id.plus_button_item_post_comment) ImageView upvoteButton;
+        @BindView(R.id.score_text_view_item_post_comment) TextView scoreTextView;
+        @BindView(R.id.minus_button_item_post_comment) ImageView downvoteButton;
+        @BindView(R.id.share_button_item_post_comment) ImageView shareButton;
+        @BindView(R.id.reply_button_item_post_comment) ImageView replyButton;
+
+        DataViewHolder(View itemView) {
+            super(itemView);
+            ButterKnife.bind(this, itemView);
+
+            verticalBlock.setVisibility(View.GONE);
+
+            authorTextView.setOnClickListener(view -> {
+                Intent intent = new Intent(mContext, ViewUserDetailActivity.class);
+                intent.putExtra(ViewUserDetailActivity.EXTRA_USER_NAME_KEY, getItem(getAdapterPosition()).getAuthor());
+                mContext.startActivity(intent);
+            });
+
+            RelativeLayout.LayoutParams lp = (RelativeLayout.LayoutParams) shareButton.getLayoutParams();
+            lp.addRule(RelativeLayout.ALIGN_PARENT_END);
+            lp.setMarginEnd(0);
+            shareButton.setLayoutParams(lp);
+
+            shareButton.setOnClickListener(view -> {
+                Intent intent = new Intent(Intent.ACTION_SEND);
+                intent.setType("text/plain");
+                String extraText = getItem(getAdapterPosition()).getPermalink();
+                intent.putExtra(Intent.EXTRA_TEXT, extraText);
+                mContext.startActivity(Intent.createChooser(intent, "Share"));
+            });
+
+            replyButton.setVisibility(View.GONE);
+
+            upvoteButton.setOnClickListener(view -> {
+                int previousVoteType = getItem(getAdapterPosition()).getVoteType();
+                String newVoteType;
+
+                downvoteButton.clearColorFilter();
+
+                if(previousVoteType != CommentData.VOTE_TYPE_UPVOTE) {
+                    //Not upvoted before
+                    getItem(getAdapterPosition()).setVoteType(CommentData.VOTE_TYPE_UPVOTE);
+                    newVoteType = RedditUtils.DIR_UPVOTE;
+                    upvoteButton.setColorFilter(ContextCompat.getColor(mContext, R.color.backgroundColorPrimaryDark), android.graphics.PorterDuff.Mode.SRC_IN);
+                } else {
+                    //Upvoted before
+                    getItem(getAdapterPosition()).setVoteType(CommentData.VOTE_TYPE_NO_VOTE);
+                    newVoteType = RedditUtils.DIR_UNVOTE;
+                    upvoteButton.clearColorFilter();
+                }
+
+                scoreTextView.setText(Integer.toString(getItem(getAdapterPosition()).getScore() + getItem(getAdapterPosition()).getVoteType()));
+
+                VoteThing.voteThing(mOauthRetrofit, mSharedPreferences, new VoteThing.VoteThingListener() {
+                    @Override
+                    public void onVoteThingSuccess(int position) {
+                        if(newVoteType.equals(RedditUtils.DIR_UPVOTE)) {
+                            getItem(getAdapterPosition()).setVoteType(CommentData.VOTE_TYPE_UPVOTE);
+                            upvoteButton.setColorFilter(ContextCompat.getColor(mContext, R.color.backgroundColorPrimaryDark), android.graphics.PorterDuff.Mode.SRC_IN);
+                        } else {
+                            getItem(getAdapterPosition()).setVoteType(CommentData.VOTE_TYPE_NO_VOTE);
+                            upvoteButton.clearColorFilter();
+                        }
+
+                        downvoteButton.clearColorFilter();
+                        scoreTextView.setText(Integer.toString(getItem(getAdapterPosition()).getScore() + getItem(getAdapterPosition()).getVoteType()));
+                    }
+
+                    @Override
+                    public void onVoteThingFail(int position) { }
+                }, getItem(getAdapterPosition()).getFullName(), newVoteType, getAdapterPosition());
+            });
+
+            downvoteButton.setOnClickListener(view -> {
+                int previousVoteType = getItem(getAdapterPosition()).getVoteType();
+                String newVoteType;
+
+                upvoteButton.clearColorFilter();
+
+                if(previousVoteType != CommentData.VOTE_TYPE_DOWNVOTE) {
+                    //Not downvoted before
+                    getItem(getAdapterPosition()).setVoteType(CommentData.VOTE_TYPE_DOWNVOTE);
+                    newVoteType = RedditUtils.DIR_DOWNVOTE;
+                    downvoteButton.setColorFilter(ContextCompat.getColor(mContext, R.color.colorAccent), android.graphics.PorterDuff.Mode.SRC_IN);
+                } else {
+                    //Downvoted before
+                    getItem(getAdapterPosition()).setVoteType(CommentData.VOTE_TYPE_NO_VOTE);
+                    newVoteType = RedditUtils.DIR_UNVOTE;
+                    downvoteButton.clearColorFilter();
+                }
+
+                scoreTextView.setText(Integer.toString(getItem(getAdapterPosition()).getScore() + getItem(getAdapterPosition()).getVoteType()));
+
+                VoteThing.voteThing(mOauthRetrofit, mSharedPreferences, new VoteThing.VoteThingListener() {
+                    @Override
+                    public void onVoteThingSuccess(int position1) {
+                        if(newVoteType.equals(RedditUtils.DIR_DOWNVOTE)) {
+                            getItem(getAdapterPosition()).setVoteType(CommentData.VOTE_TYPE_DOWNVOTE);
+                            downvoteButton.setColorFilter(ContextCompat.getColor(mContext, R.color.colorAccent), android.graphics.PorterDuff.Mode.SRC_IN);
+                        } else {
+                            getItem(getAdapterPosition()).setVoteType(CommentData.VOTE_TYPE_NO_VOTE);
+                            downvoteButton.clearColorFilter();
+                        }
+
+                        upvoteButton.clearColorFilter();
+                        scoreTextView.setText(Integer.toString(getItem(getAdapterPosition()).getScore() + getItem(getAdapterPosition()).getVoteType()));
+                    }
+
+                    @Override
+                    public void onVoteThingFail(int position1) { }
+                }, getItem(getAdapterPosition()).getFullName(), newVoteType, getAdapterPosition());
+            });
+        }
+    }
+
+    class ErrorViewHolder extends RecyclerView.ViewHolder {
+        @BindView(R.id.error_text_view_item_footer_error) TextView errorTextView;
+        @BindView(R.id.retry_button_item_footer_error) Button retryButton;
+
+        ErrorViewHolder(View itemView) {
+            super(itemView);
+            ButterKnife.bind(this, itemView);
+            errorTextView.setText(R.string.load_comments_failed);
+            retryButton.setOnClickListener(view -> mRetryLoadingMoreCallback.retryLoadingMore());
+        }
+    }
+
+    class LoadingViewHolder extends RecyclerView.ViewHolder {
+        LoadingViewHolder(@NonNull View itemView) {
+            super(itemView);
+            ButterKnife.bind(this, itemView);
+        }
+    }
+}

app/src/main/java/ml/docilealligator/infinityforreddit/JSONUtils.java

@@ -5,25 +5,20 @@ package ml.docilealligator.infinityforreddit;
  */
 
 public class JSONUtils {
-    public static final String DATA_KEY = "data";
+    static final String DATA_KEY = "data";
     static final String AFTER_KEY = "after";
-    static final String MODHASH_KEY = "modhash";
     static final String CHILDREN_KEY = "children";
     static final String COUNT_KEY = "count";
     static final String TITLE_KEY = "title";
-    public static final String NAME_KEY = "name";
+    static final String NAME_KEY = "name";
     static final String SUBREDDIT_NAME_PREFIX_KEY = "subreddit_name_prefixed";
     static final String SELFTEXT_HTML_KEY = "selftext_html";
     static final String AUTHOR_KEY = "author";
-    static final String DOMAIN_KEY = "domain";
     static final String LINK_FLAIR_TEXT_KEY = "link_flair_text";
-    static final String NUM_CROSSPOST_KEY = "num_crossposts";
-    static final String CAN_MOD_POST_KEY = "can_mod_post";
     static final String SCORE_KEY = "score";
     static final String LIKES_KEY = "likes";
     static final String NSFW_KEY = "over_18";
     static final String GILDED_KEY = "gilded";
-    static final String POST_HINT_KEY = "post_hint";
     static final String PERMALINK_KEY = "permalink";
     static final String CREATED_UTC_KEY = "created_utc";
     static final String PREVIEW_KEY = "preview";
@@ -37,12 +32,10 @@ public class JSONUtils {
     static final String URL_KEY = "url";
     static final String MEDIA_KEY = "media";
     static final String REDDIT_VIDEO_KEY = "reddit_video";
-    static final String FALLBACK_URL_KEY = "fallback_url";
     static final String DASH_URL_KEY = "dash_url";
     static final String IS_VIDEO_KEY = "is_video";
     static final String CROSSPOST_PARENT_LIST = "crosspost_parent_list";
     static final String REDDIT_VIDEO_PREVIEW_KEY = "reddit_video_preview";
-    static final String IS_REDDIT_MEDIA_DOMAIN = "is_reddit_media_domain";
     static final String STICKIED_KEY = "stickied";
     static final String BODY_HTML_KEY = "body_html";
     static final String COLLAPSED_KEY = "collapsed";
@@ -51,24 +44,22 @@ public class JSONUtils {
     static final String DEPTH_KEY = "depth";
     static final String ID_KEY = "id";
     static final String SCORE_HIDDEN_KEY = "score_hidden";
-    public static final String SUBREDDIT_KEY = "subreddit";
-    public static final String BANNER_IMG_KEY = "banner_img";
+    static final String SUBREDDIT_KEY = "subreddit";
+    static final String BANNER_IMG_KEY = "banner_img";
     static final String BANNER_BACKGROUND_IMAGE_KEY = "banner_background_image";
-    public static final String ICON_IMG_KEY = "icon_img";
+    static final String ICON_IMG_KEY = "icon_img";
     static final String COMMUNITY_ICON_KEY = "community_icon";
-    public static final String LINK_KARMA_KEY = "link_karma";
-    public static final String COMMENT_KARMA_KEY = "comment_karma";
+    static final String LINK_KARMA_KEY = "link_karma";
+    static final String COMMENT_KARMA_KEY = "comment_karma";
     static final String DISPLAY_NAME = "display_name";
     static final String SUBREDDIT_TYPE_KEY = "subreddit_type";
     static final String SUBREDDIT_TYPE_VALUE_USER = "user";
     static final String SUBSCRIBERS_KEY = "subscribers";
     static final String PUBLIC_DESCRIPTION_KEY = "public_description";
     static final String ACTIVE_USER_COUNT_KEY = "active_user_count";
-    public static final String IS_GOLD_KEY = "is_gold";
-    public static final String IS_FRIEND_KEY = "is_friend";
-    static final String KIND_KEY = "kind";
+    static final String IS_GOLD_KEY = "is_gold";
+    static final String IS_FRIEND_KEY = "is_friend";
     static final String JSON_KEY = "json";
-    static final String THINGS_KEY = "things";
     static final String PARENT_ID_KEY = "parent_id";
     static final String ERRORS_KEY = "errors";
     static final String ARGS_KEY = "args";

app/src/main/java/ml/docilealligator/infinityforreddit/ParseComment.java

@@ -211,7 +211,7 @@ class ParseComment {
         }
     }
 
-    private static CommentData parseSingleComment(JSONObject singleCommentData, int depth, Locale locale) throws JSONException {
+    static CommentData parseSingleComment(JSONObject singleCommentData, int depth, Locale locale) throws JSONException {
         String id = singleCommentData.getString(JSONUtils.ID_KEY);
         String fullName = singleCommentData.getString(JSONUtils.NAME_KEY);
         String author = singleCommentData.getString(JSONUtils.AUTHOR_KEY);

app/src/main/java/ml/docilealligator/infinityforreddit/ParsePost.java

@@ -90,15 +90,8 @@ class ParsePost {
                         return null;
                     }
 
-                    String kind = allData.getJSONObject(0).getString(JSONUtils.KIND_KEY);
-                    if(kind.equals("t3")) {
-                        //It's a post
-                        JSONObject data = allData.getJSONObject(0).getJSONObject(JSONUtils.DATA_KEY);
-                        post = parseBasicData(data, locale, -1);
-                    } else {
-                        parseFailed = true;
-                        return null;
-                    }
+                    JSONObject data = allData.getJSONObject(0).getJSONObject(JSONUtils.DATA_KEY);
+                    post = parseBasicData(data, locale, -1);
                 } else {
                     //Posts listing
                     int size;
@@ -109,12 +102,8 @@ class ParsePost {
                     }
 
                     for(int i = 0; i < size; i++) {
-                        String kind = allData.getJSONObject(i).getString(JSONUtils.KIND_KEY);
-                        if(kind.equals("t3")) {
-                            //It's a post
-                            JSONObject data = allData.getJSONObject(i).getJSONObject(JSONUtils.DATA_KEY);
-                            newPosts.add(parseBasicData(data, locale, i));
-                        }
+                        JSONObject data = allData.getJSONObject(i).getJSONObject(JSONUtils.DATA_KEY);
+                        newPosts.add(parseBasicData(data, locale, i));
                     }
                 }
             } catch (JSONException e) {

app/src/main/java/ml/docilealligator/infinityforreddit/PostDataSource.java

@@ -190,7 +190,11 @@ class PostDataSource extends PageKeyedDataSource<String, Post> {
                     ParsePost.parsePosts(response.body(), locale, -1, new ParsePost.ParsePostsListingListener() {
                         @Override
                         public void onParsePostsListingSuccess(ArrayList<Post> newPosts, String lastItem) {
-                            callback.onResult(newPosts, lastItem);
+                            if(lastItem == null || lastItem.equals("") || lastItem.equals("null")) {
+                                callback.onResult(newPosts, null);
+                            } else {
+                                callback.onResult(newPosts, lastItem);
+                            }
                             paginationNetworkStateLiveData.postValue(NetworkState.LOADED);
                         }
 
@@ -265,7 +269,11 @@ class PostDataSource extends PageKeyedDataSource<String, Post> {
                     ParsePost.parsePosts(response.body(), locale, -1, new ParsePost.ParsePostsListingListener() {
                         @Override
                         public void onParsePostsListingSuccess(ArrayList<Post> newPosts, String lastItem) {
-                            callback.onResult(newPosts, lastItem);
+                            if(lastItem == null || lastItem.equals("") || lastItem.equals("null")) {
+                                callback.onResult(newPosts, null);
+                            } else {
+                                callback.onResult(newPosts, lastItem);
+                            }
                             paginationNetworkStateLiveData.postValue(NetworkState.LOADED);
                         }
 
@@ -378,7 +386,7 @@ class PostDataSource extends PageKeyedDataSource<String, Post> {
         Call<String> getPost;
 
         if(subredditName == null) {
-            getPost = api.searchPosts(subredditName, null, RedditUtils.getOAuthHeader(accessToken));
+            getPost = api.searchPosts(query, null, RedditUtils.getOAuthHeader(accessToken));
         } else {
             getPost = api.searchPostsInSpecificSubreddit(subredditName, query, null, RedditUtils.getOAuthHeader(accessToken));
         }
@@ -438,7 +446,11 @@ class PostDataSource extends PageKeyedDataSource<String, Post> {
                     ParsePost.parsePosts(response.body(), locale, -1, new ParsePost.ParsePostsListingListener() {
                         @Override
                         public void onParsePostsListingSuccess(ArrayList<Post> newPosts, String lastItem) {
-                            callback.onResult(newPosts, lastItem);
+                            if(lastItem == null || lastItem.equals("") || lastItem.equals("null")) {
+                                callback.onResult(newPosts, null);
+                            } else {
+                                callback.onResult(newPosts, lastItem);
+                            }
                             paginationNetworkStateLiveData.postValue(NetworkState.LOADED);
                         }
 

app/src/main/java/ml/docilealligator/infinityforreddit/RedditAPI.java

@@ -48,13 +48,16 @@ public interface RedditAPI {
     Call<String> getSubredditBestPosts(@Path("subredditName") String subredditName, @Query("after") String lastItem,
                                        @HeaderMap Map<String, String> headers);
 
-    @GET("user/{userName}.json?raw_json=1&limit=25")
-    Call<String> getUserBestPosts(@Path("userName") String userName, @Query("after") String lastItem,
+    @GET("user/{username}/submitted.json?raw_json=1&limit=25")
+    Call<String> getUserBestPosts(@Path("username") String username, @Query("after") String lastItem,
                                   @HeaderMap Map<String, String> headers);
 
     @GET("user/{username}/about.json?raw_json=1")
     Call<String> getUserData(@Path("username") String username);
 
+    @GET("user/{username}/comments.json?raw_json=1")
+    Call<String> getUserComments(@Path("username") String username, @Query("after") String after);
+
     @FormUrlEncoded
     @POST("api/subscribe")
     Call<String> subredditSubscription(@HeaderMap Map<String, String> headers, @FieldMap Map<String, String> params);

app/src/main/java/ml/docilealligator/infinityforreddit/SearchActivity.java

@@ -4,6 +4,7 @@ import android.content.Intent;
 import android.os.Bundle;
 import android.view.Menu;
 import android.view.MenuItem;
+import android.view.WindowManager;
 import android.widget.RelativeLayout;
 import android.widget.TextView;
 
@@ -98,6 +99,14 @@ public class SearchActivity extends AppCompatActivity {
         }
     }
 
+    @Override
+    protected void onStart() {
+        super.onStart();
+        simpleSearchView.showSearch(false);
+        simpleSearchView.getSearchEditText().requestFocus();
+        getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_VISIBLE);
+    }
+
     @Override
     protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
         if (simpleSearchView.onActivityResult(requestCode, resultCode, data)) {

app/src/main/java/ml/docilealligator/infinityforreddit/SubredditListingRecyclerViewAdapter.java

@@ -208,7 +208,7 @@ public class SubredditListingRecyclerViewAdapter extends PagedListAdapter<Subred
             super(itemView);
             ButterKnife.bind(this, itemView);
             retryButton.setOnClickListener(view -> retryLoadingMoreCallback.retryLoadingMore());
-            errorTextView.setText(R.string.post_load_comments_failed);
+            errorTextView.setText(R.string.load_comments_failed);
         }
     }
 

app/src/main/java/ml/docilealligator/infinityforreddit/UserListingRecyclerViewAdapter.java

@@ -208,7 +208,7 @@ public class UserListingRecyclerViewAdapter extends PagedListAdapter<UserData, R
             super(itemView);
             ButterKnife.bind(this, itemView);
             retryButton.setOnClickListener(view -> retryLoadingMoreCallback.retryLoadingMore());
-            errorTextView.setText(R.string.post_load_comments_failed);
+            errorTextView.setText(R.string.load_comments_failed);
         }
     }
 

app/src/main/java/ml/docilealligator/infinityforreddit/ViewUserDetailActivity.java

@@ -15,7 +15,10 @@ import androidx.appcompat.app.AppCompatActivity;
 import androidx.appcompat.widget.Toolbar;
 import androidx.coordinatorlayout.widget.CoordinatorLayout;
 import androidx.fragment.app.Fragment;
+import androidx.fragment.app.FragmentManager;
+import androidx.fragment.app.FragmentPagerAdapter;
 import androidx.lifecycle.ViewModelProviders;
+import androidx.viewpager.widget.ViewPager;
 
 import com.bumptech.glide.Glide;
 import com.bumptech.glide.RequestManager;
@@ -24,6 +27,7 @@ import com.google.android.material.appbar.AppBarLayout;
 import com.google.android.material.appbar.CollapsingToolbarLayout;
 import com.google.android.material.chip.Chip;
 import com.google.android.material.snackbar.Snackbar;
+import com.google.android.material.tabs.TabLayout;
 
 import javax.inject.Inject;
 import javax.inject.Named;
@@ -48,7 +52,9 @@ public class ViewUserDetailActivity extends AppCompatActivity {
     private static final String IS_IN_LAZY_MODE_STATE = "IILMS";
 
     @BindView(R.id.coordinator_layout_view_user_detail_activity) CoordinatorLayout coordinatorLayout;
+    @BindView(R.id.view_pager_view_user_detail_activity) ViewPager viewPager;
     @BindView(R.id.appbar_layout_view_user_detail) AppBarLayout appBarLayout;
+    @BindView(R.id.tab_layout_view_user_detail_activity) TabLayout tabLayout;
     @BindView(R.id.collapsing_toolbar_layout_view_user_detail_activity) CollapsingToolbarLayout collapsingToolbarLayout;
     @BindView(R.id.banner_image_view_view_user_detail_activity) GifImageView bannerImageView;
     @BindView(R.id.icon_gif_image_view_view_user_detail_activity) GifImageView iconGifImageView;
@@ -56,6 +62,8 @@ public class ViewUserDetailActivity extends AppCompatActivity {
     @BindView(R.id.subscribe_user_chip_view_user_detail_activity) Chip subscribeUserChip;
     @BindView(R.id.karma_text_view_view_user_detail_activity) TextView karmaTextView;
 
+    private SectionsPagerAdapter sectionsPagerAdapter;
+
     private Fragment mFragment;
     private SubscribedUserDao subscribedUserDao;
     private RequestManager glide;
@@ -66,6 +74,8 @@ public class ViewUserDetailActivity extends AppCompatActivity {
     private String userName;
     private boolean subscriptionReady = false;
     private boolean isInLazyMode = false;
+    private int colorPrimary;
+    private int white;
 
     @Inject
     @Named("no_oauth")
@@ -108,6 +118,29 @@ public class ViewUserDetailActivity extends AppCompatActivity {
         ViewGroup.MarginLayoutParams params = (ViewGroup.MarginLayoutParams) toolbar.getLayoutParams();
         params.topMargin = statusBarHeight;
 
+        sectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
+        viewPager.setAdapter(sectionsPagerAdapter);
+        viewPager.setOffscreenPageLimit(2);
+        tabLayout.setupWithViewPager(viewPager);
+
+        colorPrimary = getResources().getColor(R.color.colorPrimary);
+        white = getResources().getColor(android.R.color.white);
+
+        appBarLayout.addOnOffsetChangedListener(new AppBarStateChangeListener() {
+            @Override
+            void onStateChanged(AppBarLayout appBarLayout, State state) {
+                if(state == State.EXPANDED) {
+                    tabLayout.setTabTextColors(colorPrimary, colorPrimary);
+                    tabLayout.setSelectedTabIndicatorColor(colorPrimary);
+                    tabLayout.setBackgroundColor(white);
+                } else if(state == State.COLLAPSED) {
+                    tabLayout.setTabTextColors(white, white);
+                    tabLayout.setSelectedTabIndicatorColor(white);
+                    tabLayout.setBackgroundColor(colorPrimary);
+                }
+            }
+        });
+
         subscribedUserDao = SubscribedUserRoomDatabase.getDatabase(this).subscribedUserDao();
         glide = Glide.with(this);
 
@@ -238,23 +271,23 @@ public class ViewUserDetailActivity extends AppCompatActivity {
         });
 
         if(savedInstanceState == null) {
-            mFragment = new PostFragment();
+            /*mFragment = new PostFragment();
             Bundle bundle = new Bundle();
             bundle.putString(PostFragment.EXTRA_SUBREDDIT_NAME_KEY, userName);
             bundle.putInt(PostFragment.EXTRA_POST_TYPE_KEY, PostDataSource.TYPE_USER);
             mFragment.setArguments(bundle);
-            getSupportFragmentManager().beginTransaction().replace(R.id.frame_layout_view_user_detail_activity, mFragment).commit();
+            getSupportFragmentManager().beginTransaction().replace(R.id.frame_layout_view_user_detail_activity, mFragment).commit();*/
         } else {
-            mFragment = getSupportFragmentManager().getFragment(savedInstanceState, FRAGMENT_OUT_STATE_KEY);
+            /*mFragment = getSupportFragmentManager().getFragment(savedInstanceState, FRAGMENT_OUT_STATE_KEY);
             if(mFragment == null) {
                 mFragment = new PostFragment();
                 Bundle bundle = new Bundle();
                 bundle.putString(PostFragment.EXTRA_SUBREDDIT_NAME_KEY, userName);
                 bundle.putInt(PostFragment.EXTRA_POST_TYPE_KEY, PostDataSource.TYPE_USER);
                 mFragment.setArguments(bundle);
-            }
+            }*/
             isInLazyMode = savedInstanceState.getBoolean(IS_IN_LAZY_MODE_STATE);
-            getSupportFragmentManager().beginTransaction().replace(R.id.frame_layout_view_user_detail_activity, mFragment).commit();
+            //getSupportFragmentManager().beginTransaction().replace(R.id.frame_layout_view_user_detail_activity, mFragment).commit();
         }
     }
 
@@ -321,13 +354,51 @@ public class ViewUserDetailActivity extends AppCompatActivity {
     protected void onSaveInstanceState(@NonNull Bundle outState) {
         super.onSaveInstanceState(outState);
         outState.putBoolean(IS_IN_LAZY_MODE_STATE, isInLazyMode);
-        getSupportFragmentManager().putFragment(outState, FRAGMENT_OUT_STATE_KEY, mFragment);
+        //getSupportFragmentManager().putFragment(outState, FRAGMENT_OUT_STATE_KEY, mFragment);
     }
 
     private void makeSnackbar(int resId) {
         Snackbar.make(coordinatorLayout, resId, Snackbar.LENGTH_SHORT).show();
     }
 
+    public abstract static class AppBarStateChangeListener implements AppBarLayout.OnOffsetChangedListener {
+        // State
+        public enum State {
+            EXPANDED,
+            COLLAPSED,
+            IDLE
+        }
+
+        private State mCurrentState = State.IDLE;
+
+        @Override
+        public final void onOffsetChanged(AppBarLayout appBarLayout, int i) {
+            if (i == 0) {
+                if (mCurrentState != State.EXPANDED) {
+                    onStateChanged(appBarLayout, State.EXPANDED);
+                }
+                mCurrentState = State.EXPANDED;
+            } else if (Math.abs(i) >= appBarLayout.getTotalScrollRange()) {
+                if (mCurrentState != State.COLLAPSED) {
+                    onStateChanged(appBarLayout, State.COLLAPSED);
+                }
+                mCurrentState = State.COLLAPSED;
+            } else {
+                if (mCurrentState != State.IDLE) {
+                    onStateChanged(appBarLayout, State.IDLE);
+                }
+                mCurrentState = State.IDLE;
+            }
+        }
+
+        /**
+         * Notifies on state change
+         * @param appBarLayout Layout
+         * @param state Collapse state
+         */
+        abstract void onStateChanged(AppBarLayout appBarLayout, State state);
+    }
+
     private static class InsertUserDataAsyncTask extends AsyncTask<Void, Void, Void> {
 
         private UserDao userDao;
@@ -344,4 +415,71 @@ public class ViewUserDetailActivity extends AppCompatActivity {
             return null;
         }
     }
+
+    private class SectionsPagerAdapter extends FragmentPagerAdapter {
+        private PostFragment postFragment;
+        private CommentsListingFragment commentsListingFragment;
+
+        SectionsPagerAdapter(FragmentManager fm) {
+            super(fm);
+        }
+
+        @NonNull
+        @Override
+        public Fragment getItem(int position) {
+            if (position == 0) {
+                PostFragment fragment = new PostFragment();
+                Bundle bundle = new Bundle();
+                bundle.putInt(PostFragment.EXTRA_POST_TYPE_KEY, PostDataSource.TYPE_USER);
+                bundle.putString(PostFragment.EXTRA_SUBREDDIT_NAME_KEY, userName);
+                fragment.setArguments(bundle);
+                return fragment;
+            }
+            CommentsListingFragment fragment = new CommentsListingFragment();
+            Bundle bundle = new Bundle();
+            bundle.putString(CommentsListingFragment.EXTRA_USERNAME_KEY, userName);
+            fragment.setArguments(bundle);
+            return fragment;
+        }
+
+        @Override
+        public int getCount() {
+            return 2;
+        }
+
+        @Override
+        public CharSequence getPageTitle(int position) {
+            switch (position) {
+                case 0:
+                    return "Posts";
+                case 1:
+                    return "Comments";
+            }
+            return null;
+        }
+
+        @NonNull
+        @Override
+        public Object instantiateItem(@NonNull ViewGroup container, int position) {
+            Fragment fragment = (Fragment) super.instantiateItem(container, position);
+            switch (position) {
+                case 0:
+                    postFragment = (PostFragment) fragment;
+                    break;
+                case 1:
+                    commentsListingFragment = (CommentsListingFragment) fragment;
+                    break;
+            }
+            return fragment;
+        }
+
+        public void refresh() {
+            if(postFragment != null) {
+                ((FragmentCommunicator) postFragment).refresh();
+            }
+            if(commentsListingFragment != null) {
+                ((FragmentCommunicator) commentsListingFragment).refresh();
+            }
+        }
+    }
 }

app/src/main/res/layout/activity_view_user_detail.xml

@@ -7,6 +7,12 @@
     android:id="@+id/coordinator_layout_view_user_detail_activity"
     tools:context=".ViewUserDetailActivity">
 
+    <androidx.viewpager.widget.ViewPager
+        android:id="@+id/view_pager_view_user_detail_activity"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        app:layout_behavior="@string/appbar_scrolling_view_behavior" />
+
     <com.google.android.material.appbar.AppBarLayout
         android:id="@+id/appbar_layout_view_user_detail"
         android:layout_width="match_parent"
@@ -94,8 +100,20 @@
 
         </com.google.android.material.appbar.CollapsingToolbarLayout>
 
+        <com.google.android.material.tabs.TabLayout
+            android:id="@+id/tab_layout_view_user_detail_activity"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_gravity="bottom"
+            app:layout_scrollFlags="scroll|enterAlways"
+            app:tabGravity="fill"
+            app:tabMode="fixed"
+            app:tabIndicatorHeight="3dp"
+            app:tabRippleColor="?attr/colorControlHighlight"
+            app:tabUnboundedRipple="false" />
+
     </com.google.android.material.appbar.AppBarLayout>
 
-    <include layout="@layout/content_view_user_detail" />
+    <!--<include layout="@layout/content_view_user_detail" />-->
 
 </androidx.coordinatorlayout.widget.CoordinatorLayout>

app/src/main/res/layout/fragment_comments_listing.xml

@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:id="@+id/coordinator_layout_comments_listing_fragment"
+    tools:context="ml.docilealligator.infinityforreddit.CommentsListingFragment">
+
+    <com.lsjwzh.widget.materialloadingprogressbar.CircleProgressBar
+        android:id="@+id/progress_bar_comments_listing_fragment"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="16dp"
+        android:layout_marginBottom="16dp"
+        app:mlpb_progress_stoke_width="3dp"
+        app:mlpb_progress_color="@color/colorAccent"
+        app:mlpb_background_color="@color/circularProgressBarBackground"
+        android:layout_gravity="center_horizontal"/>
+
+    <androidx.recyclerview.widget.RecyclerView
+        android:id="@+id/recycler_view_comments_listing_fragment"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent" />
+
+    <LinearLayout
+        android:id="@+id/fetch_comments_info_linear_layout_comments_listing_fragment"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:gravity="center"
+        android:orientation="vertical"
+        android:visibility="gone">
+
+        <ImageView
+            android:id="@+id/fetch_comments_info_image_view_comments_listing_fragment"
+            android:layout_width="150dp"
+            android:layout_height="wrap_content" />
+
+        <TextView
+            android:id="@+id/fetch_comments_info_text_view_comments_listing_fragment"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="16dp"
+            android:gravity="center" />
+
+    </LinearLayout>
+
+</androidx.coordinatorlayout.widget.CoordinatorLayout>

app/src/main/res/layout/item_load_comments_failed_placeholder.xml

@@ -15,6 +15,6 @@
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_gravity="center_horizontal"
-        android:text="@string/post_load_comments_failed"/>
+        android:text="@string/load_comments_failed"/>
 
 </LinearLayout>

app/src/main/res/values/strings.xml

@@ -33,7 +33,7 @@
     <string name="no_storage_permission">No storage permission to save this file</string>
 
     <string name="load_posts_failed">Error loading posts</string>
-    <string name="post_load_comments_failed">Error loading comments</string>
+    <string name="load_comments_failed">Error loading comments</string>
     <string name="retry">Retry</string>
     <string name="comments">Comments</string>
     <string name="no_comments_yet">No comments yet. Write a comment?</string>