[NTP Snippets] Fill space below the last snippet if necessary

chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java
index 4048be5cddb9a19c98e00fda7e0cfad87b7b5782..ac9e2a5eb7878ba3a124f1a7202a25a1396ba541 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java
@@ -15,6 +15,7 @@
 import android.view.animation.Interpolator;
 
 import org.chromium.base.Log;
+import org.chromium.base.annotations.SuppressFBWarnings;
 import org.chromium.chrome.browser.ntp.NewTabPageLayout;
 import org.chromium.chrome.browser.ntp.NewTabPageView.NewTabPageManager;
 import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
@@ -33,19 +34,37 @@
  */
 public class NewTabPageAdapter extends Adapter<NewTabPageViewHolder> implements SnippetsObserver {
     private static final String TAG = "Ntp";
+    private static final Interpolator FADE_INTERPOLATOR = new FastOutLinearInInterpolator();
 
     private final NewTabPageManager mNewTabPageManager;
     private final NewTabPageLayout mNewTabPageLayout;
     private final AboveTheFoldListItem mAboveTheFoldListItem;
     private final List<NewTabPageListItem> mNewTabPageListItems;
     private final ItemTouchCallbacks mItemTouchCallbacks;
-
-    private static final Interpolator FADE_INTERPOLATOR = new FastOutLinearInInterpolator();
+    private NewTabPageRecyclerView mRecyclerView;
 
     private class ItemTouchCallbacks extends ItemTouchHelper.Callback {
         @Override
         public void onSwiped(ViewHolder viewHolder, int direction) {
-            NewTabPageAdapter.this.dismissItem(viewHolder.getAdapterPosition());
+            mRecyclerView.onItemDismissStarted(viewHolder.itemView);
+
+            // This is going to have a effect at the next layout pass, which is going to happen
+            // after the item has been removed from the adapter and the layout.
+            mRecyclerView.refreshBottomSpacing();
+
+            NewTabPageAdapter.this.dismissItem(viewHolder);
+        }
+
+        @Override
+        public void clearView(RecyclerView recyclerView, ViewHolder viewHolder) {
+            // clearView() is called when an interaction with the item is finished, which does
+            // not mean that the user went all the way and dismissed the item before releasing it.
+            // We need to check that the item has been removed.
+            if (viewHolder.getAdapterPosition() == RecyclerView.NO_POSITION) {
+                mRecyclerView.onItemDismissFinished(viewHolder.itemView);
+            }
+
+            super.clearView(recyclerView, viewHolder);
         }
 
         @Override
@@ -123,6 +142,7 @@ public void onSnippetsReceived(List<SnippetArticle> listSnippets) {
         mNewTabPageListItems.add(mAboveTheFoldListItem);
         mNewTabPageListItems.add(new SnippetHeaderListItem());
         mNewTabPageListItems.addAll(listSnippets);
+        mNewTabPageListItems.add(new SpacingListItem());
 
         notifyDataSetChanged();
 
@@ -151,6 +171,10 @@ public NewTabPageViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
                     SnippetArticleViewHolder.createView(parent), mNewTabPageManager);
         }
 
+        if (viewType == NewTabPageListItem.VIEW_TYPE_SPACING) {
+            return new NewTabPageViewHolder(SpacingListItem.createView(parent));
+        }
+
         return null;
     }
 
@@ -164,20 +188,25 @@ public int getItemCount() {
         return mNewTabPageListItems.size();
     }
 
-    private void dismissItem(int position) {
-        assert getItemViewType(position) == NewTabPageListItem.VIEW_TYPE_SNIPPET;
-        mNewTabPageManager.onSnippetDismissed((SnippetArticle) mNewTabPageListItems.get(position));
-        mNewTabPageListItems.remove(position);
+    @SuppressFBWarnings("BC_UNCONFIRMED_CAST")

[gone, 2016/05/16 23:47:29]

Adding a type of FindBugs suppression is uglier than any adjusting the code to
account for the cast.  This will be one of only three places in the entire
codebase that checks for this instead of using instanceof, and I don't want to
have another.

[dgn, 2016/05/17 09:16:53]

Done. Do you know who FindBugs doesn't complain for the many other cases where
we wildly cast things? (findViewById for example)

[gone, 2016/05/17 16:58:19]

Honestly don't have a clue :/  I normally just do whatever is necessary to
appease FindBugs because it's *generally* correct.  Maybe it's configured to
ignore certain Android casts?  We'd have walls of warnings, otherwise.

+    @Override
+    public void onAttachedToRecyclerView(RecyclerView recyclerView) {
+        super.onAttachedToRecyclerView(recyclerView);
 
-        int numRemovedItems = 1;
-        if (mNewTabPageListItems.size() == 2) {
-            // There's only the above-the-fold item and the header left, so we remove the header.
-            position = 1; // When present, the header is always at that position.
-            mNewTabPageListItems.remove(position);
-            ++numRemovedItems;
-        }
+        // We are assuming for now that the adapter is used with a single RecyclerView.
+        // Getting the reference as we are doing here is going to be broken if that changes.
+        assert mRecyclerView == null;
+        mRecyclerView = (NewTabPageRecyclerView) recyclerView;
+    }
+
+    private void dismissItem(ViewHolder itemViewHolder) {
+        assert itemViewHolder.getItemViewType() == NewTabPageListItem.VIEW_TYPE_SNIPPET;
 
-        notifyItemRangeRemoved(position, numRemovedItems);
+        int position = itemViewHolder.getAdapterPosition();
+        mNewTabPageManager.onSnippetDismissed((SnippetArticle) mNewTabPageListItems.get(position));
+
+        mNewTabPageListItems.remove(position);
+        notifyItemRemoved(position);
     }
 
     List<NewTabPageListItem> getItemsForTesting() {