Don't calculate date header item for adapter header

Fixes #6098
// FREEBIE

res/layout/conversation_fragment.xml

@@ -6,6 +6,13 @@
              xmlns:app="http://schemas.android.com/apk/res-auto"
              xmlns:tools="http://schemas.android.com/tools">
 
+    <android.support.v7.widget.RecyclerView
+            android:id="@android:id/list"
+            android:layout_width="match_parent"
+            android:layout_height="match_parent"
+            android:scrollbars="vertical"
+            android:cacheColorHint="?conversation_background" />
+
     <TextView android:id="@+id/scroll_date_header"
               android:layout_width="wrap_content"
               android:layout_height="wrap_content"
@@ -22,13 +29,6 @@
               android:visibility="gone"
               tools:text="March 1, 2015" />
 
-    <android.support.v7.widget.RecyclerView
-            android:id="@android:id/list"
-            android:layout_width="match_parent"
-            android:layout_height="match_parent"
-            android:scrollbars="vertical"
-            android:cacheColorHint="?conversation_background" />
-
     <View android:id="@+id/compose_divider"
           android:layout_width="match_parent"
           android:layout_height="2dp"

src/org/thoughtcrime/securesms/ConversationAdapter.java

@@ -288,7 +288,10 @@ public class ConversationAdapter <V extends View & BindableConversationItem>
 
   @Override
   public long getHeaderId(int position) {
-    if (!isActiveCursor()) return -1;
+    if (!isActiveCursor())          return -1;
+    if (isHeaderPosition(position)) return -1;
+    if (isFooterPosition(position)) return -1;
+    if (position >= getItemCount()) return -1;
 
     Cursor        cursor = getCursorAtPositionOrThrow(position);
     MessageRecord record = getMessageRecord(cursor);

src/org/thoughtcrime/securesms/ConversationFragment.java

@@ -488,7 +488,9 @@ public class ConversationFragment extends Fragment
     }
 
     private void bindScrollHeader(HeaderViewHolder headerViewHolder, int positionId) {
-      ((ConversationAdapter)list.getAdapter()).onBindHeaderViewHolder(headerViewHolder, positionId);
+      if (((ConversationAdapter)list.getAdapter()).getHeaderId(positionId) != -1) {
+        ((ConversationAdapter) list.getAdapter()).onBindHeaderViewHolder(headerViewHolder, positionId);
+      }
     }
   }
 

src/org/thoughtcrime/securesms/database/CursorRecyclerViewAdapter.java

@@ -187,11 +187,11 @@ public abstract class CursorRecyclerViewAdapter<VH extends RecyclerView.ViewHold
     return valid && cursor != null;
   }
 
-  private boolean isFooterPosition(int position) {
+  protected boolean isFooterPosition(int position) {
     return hasFooterView() && position == getItemCount() - 1;
   }
 
-  private boolean isHeaderPosition(int position) {
+  protected boolean isHeaderPosition(int position) {
     return hasHeaderView() && position == 0;
   }
 

src/org/thoughtcrime/securesms/util/StickyHeaderDecoration.java

@@ -7,6 +7,7 @@ import android.support.v4.view.ViewCompat;
 import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.RecyclerView;
 import android.support.v7.widget.RecyclerView.ViewHolder;
+import android.util.Log;
 import android.view.View;
 import android.view.ViewGroup;
 
@@ -58,15 +59,19 @@ public class StickyHeaderDecoration extends RecyclerView.ItemDecoration {
 
   private boolean hasHeader(RecyclerView parent, StickyHeaderAdapter adapter, int adapterPos) {
     boolean isReverse = isReverseLayout(parent);
+    int     itemCount = ((RecyclerView.Adapter)adapter).getItemCount();
 
-    if (isReverse && adapterPos == ((RecyclerView.Adapter)adapter).getItemCount() - 1 || !isReverse && adapterPos == 0) {
+    if ((isReverse && adapterPos == itemCount - 1 && adapter.getHeaderId(adapterPos) != -1) ||
+        (!isReverse && adapterPos == 0))
+    {
       return true;
     }
 
-    int  previous = adapterPos + (isReverse ? 1 : -1);
-    long headerId = adapter.getHeaderId(adapterPos);
+    int  previous         = adapterPos + (isReverse ? 1 : -1);
+    long headerId         = adapter.getHeaderId(adapterPos);
+    long previousHeaderId = adapter.getHeaderId(previous);
 
-    return headerId != NO_HEADER_ID && (headerId != adapter.getHeaderId(previous));
+    return headerId != NO_HEADER_ID && previousHeaderId != NO_HEADER_ID && headerId != previousHeaderId;
   }
 
   private ViewHolder getHeader(RecyclerView parent, StickyHeaderAdapter adapter, int position) {