Make the sticky date header only visible during scroll

// FREEBIE

res/anim/slide_from_top.xml

@@ -1,5 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
 <set xmlns:android="http://schemas.android.com/apk/res/android" >
+    <alpha android:duration="1"
+           android:fromAlpha="0"
+           android:toAlpha="1"/>
+
     <translate
             android:duration="250"
             android:fromYDelta="-100%"

res/layout/conversation_fragment.xml

@@ -3,7 +3,24 @@
 <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="fill_parent"
              android:layout_height="match_parent"
-             xmlns:app="http://schemas.android.com/apk/res-auto">
+             xmlns:app="http://schemas.android.com/apk/res-auto"
+             xmlns:tools="http://schemas.android.com/tools">
+
+    <TextView android:id="@+id/scroll_date_header"
+              android:layout_width="wrap_content"
+              android:layout_height="wrap_content"
+              android:gravity="center"
+              android:layout_gravity="center_horizontal|top"
+              android:paddingLeft="6dp"
+              android:paddingRight="6dp"
+              android:paddingTop="3dp"
+              android:paddingBottom="3dp"
+              android:layout_marginTop="3dp"
+              android:textColor="@color/white"
+              android:background="?conversation_item_header_background"
+              android:textSize="14sp"
+              android:visibility="gone"
+              tools:text="March 1, 2015" />
 
     <android.support.v7.widget.RecyclerView
             android:id="@android:id/list"

src/org/thoughtcrime/securesms/ContactSelectionListFragment.java

@@ -124,7 +124,7 @@ public class ContactSelectionListFragment extends    Fragment
                                                                           isMulti());
     selectedContacts = adapter.getSelectedContacts();
     recyclerView.setAdapter(adapter);
-    recyclerView.addItemDecoration(new StickyHeaderDecoration(adapter, true));
+    recyclerView.addItemDecoration(new StickyHeaderDecoration(adapter, true, true));
     this.getLoaderManager().initLoader(0, null, this);
   }
 

src/org/thoughtcrime/securesms/ConversationAdapter.java

@@ -105,13 +105,18 @@ public class ConversationAdapter <V extends View & BindableConversationItem>
 
 
   protected static class HeaderViewHolder extends RecyclerView.ViewHolder {
-    private TextView textView;
+    protected TextView textView;
 
     public HeaderViewHolder(View itemView) {
       super(itemView);
       textView = ViewUtil.findById(itemView, R.id.text);
     }
 
+    public HeaderViewHolder(TextView textView) {
+      super(textView);
+      this.textView = textView;
+    }
+
     public void setText(CharSequence text) {
       textView.setText(text);
     }
@@ -283,6 +288,8 @@ public class ConversationAdapter <V extends View & BindableConversationItem>
 
   @Override
   public long getHeaderId(int position) {
+    if (!isActiveCursor()) return -1;
+
     Cursor        cursor = getCursorAtPositionOrThrow(position);
     MessageRecord record = getMessageRecord(cursor);
 
@@ -300,10 +307,5 @@ public class ConversationAdapter <V extends View & BindableConversationItem>
     Cursor cursor = getCursorAtPositionOrThrow(position);
     viewHolder.setText(DateUtils.getRelativeDate(getContext(), locale, getMessageRecord(cursor).getDateReceived()));
   }
-
-  @Override
-  public boolean isActive() {
-    return isActiveCursor();
-  }
 }
 

src/org/thoughtcrime/securesms/ConversationFragment.java

@@ -47,8 +47,10 @@ import android.view.ViewGroup;
 import android.view.Window;
 import android.view.animation.Animation;
 import android.view.animation.AnimationUtils;
+import android.widget.TextView;
 import android.widget.Toast;
 
+import org.thoughtcrime.securesms.ConversationAdapter.HeaderViewHolder;
 import org.thoughtcrime.securesms.ConversationAdapter.ItemClickListener;
 import org.thoughtcrime.securesms.crypto.MasterSecret;
 import org.thoughtcrime.securesms.database.DatabaseFactory;
@@ -94,6 +96,7 @@ public class ConversationFragment extends Fragment
   private View         loadMoreView;
   private View         composeDivider;
   private View         scrollToBottomButton;
+  private TextView     scrollDateHeader;
 
   @Override
   public void onCreate(Bundle icicle) {
@@ -108,6 +111,7 @@ public class ConversationFragment extends Fragment
     list                 = ViewUtil.findById(view, android.R.id.list);
     composeDivider       = ViewUtil.findById(view, R.id.compose_divider);
     scrollToBottomButton = ViewUtil.findById(view, R.id.scroll_to_bottom_button);
+    scrollDateHeader     = ViewUtil.findById(view, R.id.scroll_date_header);
 
     scrollToBottomButton.setOnClickListener(new OnClickListener() {
       @Override
@@ -185,7 +189,7 @@ public class ConversationFragment extends Fragment
     if (this.recipients != null && this.threadId != -1) {
       ConversationAdapter adapter = new ConversationAdapter(getActivity(), masterSecret, locale, selectionClickListener, null, this.recipients);
       list.setAdapter(adapter);
-      list.addItemDecoration(new StickyHeaderDecoration(adapter, false));
+      list.addItemDecoration(new StickyHeaderDecoration(adapter, false, false));
 
       getLoaderManager().restartLoader(0, Bundle.EMPTY, this);
     }
@@ -415,13 +419,16 @@ public class ConversationFragment extends Fragment
 
     private final Animation              scrollButtonInAnimation;
     private final Animation              scrollButtonOutAnimation;
+    private final ConversationDateHeader conversationDateHeader;
 
     private boolean wasAtBottom           = true;
     private boolean wasAtZoomScrollHeight = false;
+    private long    lastPositionId        = -1;
 
     ConversationScrollListener(@NonNull Context context) {
       this.scrollButtonInAnimation  = AnimationUtils.loadAnimation(context, R.anim.fade_scale_in);
       this.scrollButtonOutAnimation = AnimationUtils.loadAnimation(context, R.anim.fade_scale_out);
+      this.conversationDateHeader   = new ConversationDateHeader(context, scrollDateHeader);
 
       this.scrollButtonInAnimation.setDuration(100);
       this.scrollButtonOutAnimation.setDuration(50);
@@ -431,6 +438,7 @@ public class ConversationFragment extends Fragment
     public void onScrolled(final RecyclerView rv, final int dx, final int dy) {
       boolean currentlyAtBottom           = isAtBottom();
       boolean currentlyAtZoomScrollHeight = isAtZoomScrollHeight();
+      int     positionId                  = getHeaderPositionId();
 
       if (currentlyAtBottom && !wasAtBottom) {
         ViewUtil.fadeOut(composeDivider, 50, View.INVISIBLE);
@@ -443,8 +451,22 @@ public class ConversationFragment extends Fragment
         ViewUtil.animateIn(scrollToBottomButton, scrollButtonInAnimation);
       }
 
+      if (positionId != lastPositionId) {
+        bindScrollHeader(conversationDateHeader, positionId);
+      }
+
       wasAtBottom           = currentlyAtBottom;
       wasAtZoomScrollHeight = currentlyAtZoomScrollHeight;
+      lastPositionId        = positionId;
+    }
+
+    @Override
+    public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
+      if (newState == RecyclerView.SCROLL_STATE_DRAGGING) {
+        conversationDateHeader.show();
+      } else if (newState == RecyclerView.SCROLL_STATE_IDLE) {
+        conversationDateHeader.hide();
+      }
     }
 
     private boolean isAtBottom() {
@@ -460,6 +482,14 @@ public class ConversationFragment extends Fragment
     private boolean isAtZoomScrollHeight() {
       return ((LinearLayoutManager) list.getLayoutManager()).findFirstCompletelyVisibleItemPosition() > 4;
     }
+
+    private int getHeaderPositionId() {
+      return ((LinearLayoutManager)list.getLayoutManager()).findLastVisibleItemPosition();
+    }
+
+    private void bindScrollHeader(HeaderViewHolder headerViewHolder, int positionId) {
+      ((ConversationAdapter)list.getAdapter()).onBindHeaderViewHolder(headerViewHolder, positionId);
+    }
   }
 
   private class ConversationFragmentItemClickListener implements ItemClickListener {
@@ -553,4 +583,43 @@ public class ConversationFragment extends Fragment
       return false;
     }
   }
+
+  private static class ConversationDateHeader extends HeaderViewHolder {
+
+    private final Animation animateIn;
+    private final Animation animateOut;
+
+    private boolean pendingHide = false;
+
+    private ConversationDateHeader(Context context, TextView textView) {
+      super(textView);
+      this.animateIn  = AnimationUtils.loadAnimation(context, R.anim.slide_from_top);
+      this.animateOut = AnimationUtils.loadAnimation(context, R.anim.slide_to_top);
+
+      this.animateIn.setDuration(100);
+      this.animateOut.setDuration(100);
+    }
+
+    public void show() {
+      if (pendingHide) {
+        pendingHide = false;
+      } else {
+        ViewUtil.animateIn(textView, animateIn);
+      }
+    }
+
+    public void hide() {
+      pendingHide = true;
+
+      textView.postDelayed(new Runnable() {
+        @Override
+        public void run() {
+          if (pendingHide) {
+            pendingHide = false;
+            ViewUtil.animateOut(textView, animateOut, View.GONE);
+          }
+        }
+      }, 400);
+    }
+  }
 }

src/org/thoughtcrime/securesms/contacts/ContactSelectionListAdapter.java

@@ -103,6 +103,8 @@ public class ContactSelectionListAdapter extends CursorRecyclerViewAdapter<ViewH
 
   @Override
   public long getHeaderId(int i) {
+    if (!isActiveCursor()) return -1;
+
     return Util.hashCode(getHeaderString(i), isPush(i));
   }
 
@@ -145,11 +147,6 @@ public class ContactSelectionListAdapter extends CursorRecyclerViewAdapter<ViewH
     return getHeaderString(position);
   }
 
-  @Override
-  public boolean isActive() {
-    return isActiveCursor();
-  }
-
   public Map<Long, String> getSelectedContacts() {
     return selectedContacts;
   }

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

@@ -7,7 +7,6 @@ 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;
 
@@ -22,17 +21,21 @@ public class StickyHeaderDecoration extends RecyclerView.ItemDecoration {
 
   private static final String TAG = StickyHeaderDecoration.class.getName();
 
+  private static final long NO_HEADER_ID = -1L;
+
   private final Map<Long, ViewHolder> headerCache;
   private final StickyHeaderAdapter   adapter;
   private final boolean               renderInline;
+  private       boolean               sticky;
 
   /**
    * @param adapter the sticky header adapter to use
    */
-  public StickyHeaderDecoration(StickyHeaderAdapter adapter, boolean renderInline) {
+  public StickyHeaderDecoration(StickyHeaderAdapter adapter, boolean renderInline, boolean sticky) {
     this.adapter      = adapter;
     this.headerCache  = new HashMap<>();
     this.renderInline = renderInline;
+    this.sticky       = sticky;
   }
 
   /**
@@ -43,8 +46,8 @@ public class StickyHeaderDecoration extends RecyclerView.ItemDecoration {
                              RecyclerView.State state)
   {
     int position     = parent.getChildAdapterPosition(view);
-
     int headerHeight = 0;
+
     if (position != RecyclerView.NO_POSITION && hasHeader(parent, adapter, position)) {
       View header = getHeader(parent, adapter, position).itemView;
       headerHeight = getHeaderHeightForLayout(header);
@@ -56,16 +59,14 @@ public class StickyHeaderDecoration extends RecyclerView.ItemDecoration {
   private boolean hasHeader(RecyclerView parent, StickyHeaderAdapter adapter, int adapterPos) {
     boolean isReverse = isReverseLayout(parent);
 
-    if (!adapter.isActive()) {
-      return false;
-    }
-
     if (isReverse && adapterPos == ((RecyclerView.Adapter)adapter).getItemCount() - 1 || !isReverse && adapterPos == 0) {
       return true;
     }
 
     int  previous = adapterPos + (isReverse ? 1 : -1);
-    return adapter.getHeaderId(adapterPos) != adapter.getHeaderId(previous);
+    long headerId = adapter.getHeaderId(adapterPos);
+
+    return headerId != NO_HEADER_ID && (headerId != adapter.getHeaderId(previous));
   }
 
   private ViewHolder getHeader(RecyclerView parent, StickyHeaderAdapter adapter, int position) {
@@ -109,7 +110,7 @@ public class StickyHeaderDecoration extends RecyclerView.ItemDecoration {
 
       final int adapterPos = parent.getChildAdapterPosition(child);
 
-      if (adapterPos != RecyclerView.NO_POSITION && ((layoutPos == 0 && adapter.isActive()) || hasHeader(parent, adapter, adapterPos))) {
+      if (adapterPos != RecyclerView.NO_POSITION && ((layoutPos == 0 && sticky) || hasHeader(parent, adapter, adapterPos))) {
         View header = getHeader(parent, adapter, adapterPos).itemView;
         c.save();
         final int left = child.getLeft();
@@ -146,7 +147,7 @@ public class StickyHeaderDecoration extends RecyclerView.ItemDecoration {
         }
       }
 
-      top = Math.max(0, top);
+      if (sticky) top = Math.max(0, top);
     }
 
     return top;
@@ -204,7 +205,5 @@ public class StickyHeaderDecoration extends RecyclerView.ItemDecoration {
      * @param position the header's item position
      */
     void onBindHeaderViewHolder(T viewHolder, int position);
-
-    boolean isActive();
   }
 }