Add a Fab to scroll down parent comments. Use volume up and down keys to navigate parent comments.

app/src/main/java/ml/docilealligator/infinityforreddit/Activity/ViewPostDetailActivity.java

@@ -6,6 +6,7 @@ import android.content.res.Configuration;
 import android.content.res.Resources;
 import android.os.Build;
 import android.os.Bundle;
+import android.view.KeyEvent;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
@@ -23,6 +24,7 @@ import androidx.annotation.Nullable;
 import androidx.appcompat.widget.Toolbar;
 import androidx.coordinatorlayout.widget.CoordinatorLayout;
 import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.LinearSmoothScroller;
 import androidx.recyclerview.widget.RecyclerView;
 
 import com.bumptech.glide.Glide;
@@ -30,6 +32,7 @@ import com.bumptech.glide.RequestManager;
 import com.evernote.android.state.State;
 import com.google.android.material.appbar.AppBarLayout;
 import com.google.android.material.dialog.MaterialAlertDialogBuilder;
+import com.google.android.material.floatingactionbutton.FloatingActionButton;
 import com.google.android.material.snackbar.Snackbar;
 import com.livefront.bridge.Bridge;
 import com.r0adkll.slidr.Slidr;
@@ -142,6 +145,8 @@ public class ViewPostDetailActivity extends BaseActivity implements FlairBottomS
     ImageView mFetchPostInfoImageView;
     @BindView(R.id.fetch_post_info_text_view_view_post_detail_activity)
     TextView mFetchPostInfoTextView;
+    @BindView(R.id.fab_view_post_detail_activity)
+    FloatingActionButton fab;
     @Inject
     @Named("no_oauth")
     Retrofit mRetrofit;
@@ -164,8 +169,10 @@ public class ViewPostDetailActivity extends BaseActivity implements FlairBottomS
     private boolean mShowElapsedTime;
     private boolean showToast = false;
     private boolean isSortingComments = false;
+    private boolean mVolumeKeysNavigateComments;
     private LinearLayoutManager mLinearLayoutManager;
     private CommentAndPostRecyclerViewAdapter mAdapter;
+    private RecyclerView.SmoothScroller mSmoothScroller;
     private PostCommentSortTypeBottomSheetFragment postCommentSortTypeBottomSheetFragment;
 
     @Override
@@ -241,12 +248,19 @@ public class ViewPostDetailActivity extends BaseActivity implements FlairBottomS
         mNeedBlurSpoiler = mSharedPreferences.getBoolean(SharedPreferencesUtils.BLUR_SPOILER_KEY, false);
         mVoteButtonsOnTheRight = mSharedPreferences.getBoolean(SharedPreferencesUtils.VOTE_BUTTONS_ON_THE_RIGHT_KEY, false);
         mShowElapsedTime = mSharedPreferences.getBoolean(SharedPreferencesUtils.SHOW_ELAPSED_TIME_KEY, false);
+        mVolumeKeysNavigateComments = mSharedPreferences.getBoolean(SharedPreferencesUtils.VOLUME_KEYS_NAVIGATE_COMMENTS, false);
 
         mGlide = Glide.with(this);
         mLocale = getResources().getConfiguration().locale;
 
         mLinearLayoutManager = new LinearLayoutManager(this);
         mRecyclerView.setLayoutManager(mLinearLayoutManager);
+        mSmoothScroller = new LinearSmoothScroller(this) {
+            @Override
+            protected int getVerticalSnapPreference() {
+                return LinearSmoothScroller.SNAP_TO_START;
+            }
+        };
 
         mSingleCommentId = getIntent().getStringExtra(EXTRA_SINGLE_COMMENT_ID);
         if (savedInstanceState == null) {
@@ -433,6 +447,8 @@ public class ViewPostDetailActivity extends BaseActivity implements FlairBottomS
                 }
             }
         }
+
+        fab.setOnClickListener(view -> scrollToNextParentComment());
     }
 
 
@@ -965,6 +981,38 @@ public class ViewPostDetailActivity extends BaseActivity implements FlairBottomS
         refresh(false, true);
     }
 
+    public void scrollToNextParentComment() {
+        if (mLinearLayoutManager != null) {
+            int currentPosition = mLinearLayoutManager.findFirstVisibleItemPosition();
+            if (mAdapter != null) {
+                int nextParentPosition = mAdapter.getNextParentCommentPosition(currentPosition);
+                if (nextParentPosition < 0) {
+                    return;
+                }
+                mSmoothScroller.setTargetPosition(nextParentPosition);
+                if (mLinearLayoutManager != null) {
+                    mLinearLayoutManager.startSmoothScroll(mSmoothScroller);
+                }
+            }
+        }
+    }
+
+    public void scrollToPreviousParentComment() {
+        if (mLinearLayoutManager != null) {
+            int currentPosition = mLinearLayoutManager.findFirstVisibleItemPosition();
+            if (mAdapter != null) {
+                int nextParentPosition = mAdapter.getPreviousParentCommentPosition(currentPosition);
+                if (nextParentPosition < 0) {
+                    return;
+                }
+                mSmoothScroller.setTargetPosition(nextParentPosition);
+                if (mLinearLayoutManager != null) {
+                    mLinearLayoutManager.startSmoothScroll(mSmoothScroller);
+                }
+            }
+        }
+    }
+
     @Subscribe
     public void onPostUpdateEvent(PostUpdateEventToDetailActivity event) {
         if (mPost.getId().equals(event.post.getId())) {
@@ -1294,7 +1342,7 @@ public class ViewPostDetailActivity extends BaseActivity implements FlairBottomS
                 refresh(true, false);
             }
         } else if (requestCode == EDIT_COMMENT_REQUEST_CODE) {
-            if (resultCode == RESULT_OK) {
+            if (data != null && resultCode == RESULT_OK) {
                 mAdapter.editComment(data.getStringExtra(EditCommentActivity.EXTRA_EDITED_COMMENT_CONTENT),
                         data.getExtras().getInt(EditCommentActivity.EXTRA_EDITED_COMMENT_POSITION));
             }
@@ -1324,6 +1372,21 @@ public class ViewPostDetailActivity extends BaseActivity implements FlairBottomS
         Bridge.clear(this);
     }
 
+    @Override
+    public boolean onKeyDown(int keyCode, KeyEvent event) {
+        if (mVolumeKeysNavigateComments) {
+            switch (keyCode) {
+                case KeyEvent.KEYCODE_VOLUME_UP:
+                    scrollToPreviousParentComment();
+                    return true;
+                case KeyEvent.KEYCODE_VOLUME_DOWN:
+                    scrollToNextParentComment();
+                    return true;
+            }
+        }
+        return super.onKeyDown(keyCode, event);
+    }
+
     @Override
     public void flairSelected(Flair flair) {
         Map<String, String> params = new HashMap<>();

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

@@ -1437,6 +1437,44 @@ public class CommentAndPostRecyclerViewAdapter extends RecyclerView.Adapter<Recy
         mNeedBlurSpoiler = needBlurSpoiler;
     }
 
+    public int getNextParentCommentPosition(int currentPosition) {
+        if (mVisibleComments != null && !mVisibleComments.isEmpty()) {
+            if (mIsSingleCommentThreadMode) {
+                for (int i = currentPosition + 1; i - 2 < mVisibleComments.size(); i++) {
+                    if (mVisibleComments.get(i - 2).getDepth() == 0) {
+                        return i;
+                    }
+                }
+            } else {
+                for (int i = currentPosition + 1; i - 1 < mVisibleComments.size(); i++) {
+                    if (mVisibleComments.get(i - 1).getDepth() == 0) {
+                        return i;
+                    }
+                }
+            }
+        }
+        return -1;
+    }
+
+    public int getPreviousParentCommentPosition(int currentPosition) {
+        if (mVisibleComments != null && !mVisibleComments.isEmpty()) {
+            if (mIsSingleCommentThreadMode) {
+                for (int i = currentPosition + 1; i - 2 >= 0; i--) {
+                    if (mVisibleComments.get(i - 2).getDepth() == 0) {
+                        return i;
+                    }
+                }
+            } else {
+                for (int i = currentPosition - 1; i - 1 >= 0; i--) {
+                    if (mVisibleComments.get(i - 1).getDepth() == 0) {
+                        return i;
+                    }
+                }
+            }
+        }
+        return -1;
+    }
+
     @Override
     public void onViewRecycled(@NonNull RecyclerView.ViewHolder holder) {
         if (holder instanceof CommentViewHolder) {

app/src/main/java/ml/docilealligator/infinityforreddit/Utils/SharedPreferencesUtils.java

@@ -58,4 +58,5 @@ public class SharedPreferencesUtils {
     public static final String PULL_NOTIFICATION_TIME = "pull_notification_time";
     public static final String SHOW_ELAPSED_TIME_KEY = "show_elapsed_time";
     public static final String SWIPE_RIGHT_TO_GO_BACK_FROM_POST_DETAIL = "swipe_to_go_back_from_post_detail";
+    public static final String VOLUME_KEYS_NAVIGATE_COMMENTS = "volume_keys_navigate_comments";
 }

app/src/main/res/drawable/ic_keyboard_arrow_down_24dp.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+  <path
+      android:fillColor="#FFFFFFFF"
+      android:pathData="M7.41,8.59L12,13.17l4.59,-4.58L18,10l-6,6 -6,-6 1.41,-1.41z"/>
+</vector>

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

@@ -70,4 +70,14 @@
 
     </LinearLayout>
 
+    <com.google.android.material.floatingactionbutton.FloatingActionButton
+        android:id="@+id/fab_view_post_detail_activity"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="bottom|end"
+        android:layout_margin="@dimen/fab_margin"
+        app:backgroundTint="@color/backgroundColorPrimary"
+        app:tint="@android:color/white"
+        app:srcCompat="@drawable/ic_keyboard_arrow_down_24dp" />
+
 </androidx.coordinatorlayout.widget.CoordinatorLayout>

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

@@ -289,6 +289,7 @@
     <string name="settings_amoled_dark_title">Amoled Dark</string>
     <string name="settings_immersive_interface_title">Immersive Interface</string>
     <string name="settings_vote_buttons_on_the_right_title">Vote Buttons on the Right</string>
+    <string name="settings_volume_keys_navigate_comments_title">Use Volume Keys to Navigate Comments in Posts</string>
     <string name="settings_show_elapsed_time">Show Elpased Time in Posts and Comments</string>
     <string name="swipe_to_go_back_from_post_detail">Swipe Right to Go Back From Comments</string>
     <string name="settings_lazy_mode_interval_title">Lazy Mode Interval</string>

app/src/main/res/xml/main_preferences.xml

@@ -29,17 +29,22 @@
     <SwitchPreference
         app:defaultValue="false"
         app:key="vote_buttons_on_the_right"
-        app:title="@string/settings_vote_buttons_on_the_right_title"/>
+        app:title="@string/settings_vote_buttons_on_the_right_title" />
 
     <SwitchPreference
         app:defaultValue="false"
         app:key="show_elapsed_time"
-        app:title="@string/settings_show_elapsed_time"/>
+        app:title="@string/settings_show_elapsed_time" />
 
     <SwitchPreference
         app:defaultValue="true"
         app:key="swipe_to_go_back_from_post_detail"
-        app:title="@string/swipe_to_go_back_from_post_detail"/>
+        app:title="@string/swipe_to_go_back_from_post_detail" />
+
+    <SwitchPreference
+        app:defaultValue="false"
+        app:key="volume_keys_navigate_comments"
+        app:title="@string/settings_volume_keys_navigate_comments_title" />
 
     <Preference
         app:title="@string/settings_font_size_title"