Update look and feel of fast-scroll-to-bottom

Closes #6086
// FREEBIE

res/layout/conversation_fragment.xml

@@ -2,7 +2,8 @@
 
 <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="fill_parent"
-             android:layout_height="match_parent">
+             android:layout_height="match_parent"
+             xmlns:app="http://schemas.android.com/apk/res-auto">
 
     <android.support.v7.widget.RecyclerView
             android:id="@android:id/list"
@@ -11,26 +12,29 @@
             android:scrollbars="vertical"
             android:cacheColorHint="?conversation_background" />
 
-
-    <!--suppress AndroidLintUnusedAttribute-->
     <View android:id="@+id/compose_divider"
           android:layout_width="match_parent"
           android:layout_height="2dp"
           android:layout_gravity="bottom"
           android:background="@drawable/compose_divider_background"
-          android:alpha="0"
+          android:alpha="1"
           android:visibility="invisible" />
 
-    <android.support.design.widget.FloatingActionButton
-        android:id="@+id/scroll_to_bottom_button"
-        android:visibility="invisible"
-        android:layout_width="wrap_content"
-        android:layout_height="wrap_content"
-        android:layout_marginEnd="@dimen/scroll_to_bottom_button_margin_end"
-        android:layout_marginRight="@dimen/scroll_to_bottom_button_margin_end"
-        android:layout_marginBottom="@dimen/scroll_to_bottom_button_margin_bottom"
-        android:layout_gravity="bottom|end"
-        android:contentDescription="@string/conversation_fragment__scroll_to_the_bottom_content_description"
-        android:src="@drawable/ic_keyboard_arrow_down_white_36dp" />
+    <ImageButton
+            android:id="@+id/scroll_to_bottom_button"
+            android:visibility="gone"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginEnd="10dp"
+            android:layout_marginRight="10dp"
+            android:layout_marginBottom="10dp"
+            android:padding="5dp"
+            android:layout_gravity="bottom|end"
+            android:background="@drawable/circle_tintable"
+            android:tint="@color/grey_600"
+            android:elevation="1dp"
+            android:alpha="0.9"
+            android:contentDescription="@string/conversation_fragment__scroll_to_the_bottom_content_description"
+            android:src="@drawable/ic_scroll_down"/>
 
 </FrameLayout>

res/values/dimens.xml

@@ -66,7 +66,4 @@
     <dimen name="onboarding_subtitle_size">20sp</dimen>
 
     <dimen name="scribble_stroke_size">3dp</dimen>
-
-    <dimen name="scroll_to_bottom_button_margin_end">10dp</dimen>
-    <dimen name="scroll_to_bottom_button_margin_bottom">10dp</dimen>
 </resources>

src/org/thoughtcrime/securesms/ConversationFragment.java

@@ -24,6 +24,7 @@ import android.database.Cursor;
 import android.os.AsyncTask;
 import android.os.Build;
 import android.os.Bundle;
+import android.support.annotation.NonNull;
 import android.support.v4.app.Fragment;
 import android.support.v4.app.LoaderManager;
 import android.support.v4.content.Loader;
@@ -44,6 +45,8 @@ import android.view.View;
 import android.view.View.OnClickListener;
 import android.view.ViewGroup;
 import android.view.Window;
+import android.view.animation.Animation;
+import android.view.animation.AnimationUtils;
 import android.widget.Toast;
 
 import org.thoughtcrime.securesms.ConversationAdapter.ItemClickListener;
@@ -79,7 +82,6 @@ public class ConversationFragment extends Fragment
 
   private final ActionModeCallback actionModeCallback     = new ActionModeCallback();
   private final ItemClickListener  selectionClickListener = new ConversationFragmentItemClickListener();
-  private final OnScrollListener   scrollListener         = new ConversationScrollListener();
 
   private ConversationFragmentListener listener;
 
@@ -117,7 +119,6 @@ public class ConversationFragment extends Fragment
     final LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.VERTICAL, true);
     list.setHasFixedSize(false);
     list.setLayoutManager(layoutManager);
-    list.addOnScrollListener(scrollListener);
     list.setItemAnimator(null);
 
     loadMoreView = inflater.inflate(R.layout.load_more_header, container, false);
@@ -173,8 +174,11 @@ public class ConversationFragment extends Fragment
   }
 
   private void initializeResources() {
-    this.recipients = RecipientFactory.getRecipientsForIds(getActivity(), getActivity().getIntent().getLongArrayExtra("recipients"), true);
-    this.threadId   = this.getActivity().getIntent().getLongExtra("thread_id", -1);
+    this.recipients     = RecipientFactory.getRecipientsForIds(getActivity(), getActivity().getIntent().getLongArrayExtra("recipients"), true);
+    this.threadId       = this.getActivity().getIntent().getLongExtra("thread_id", -1);
+
+    OnScrollListener scrollListener = new ConversationScrollListener(getActivity());
+    list.addOnScrollListener(scrollListener);
   }
 
   private void initializeListAdapter() {
@@ -408,26 +412,39 @@ public class ConversationFragment extends Fragment
   }
 
   private class ConversationScrollListener extends OnScrollListener {
-    private boolean wasAtBottom = true;
+
+    private final Animation scrollButtonInAnimation;
+    private final Animation scrollButtonOutAnimation;
+
+    private boolean wasAtBottom           = true;
+    private boolean wasAtZoomScrollHeight = false;
+
+    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.scrollButtonInAnimation.setDuration(100);
+      this.scrollButtonOutAnimation.setDuration(50);
+    }
 
     @Override
     public void onScrolled(final RecyclerView rv, final int dx, final int dy) {
-      boolean currentlyAtBottom = isAtBottom();
+      boolean currentlyAtBottom           = isAtBottom();
+      boolean currentlyAtZoomScrollHeight = isAtZoomScrollHeight();
 
-      if (wasAtBottom != currentlyAtBottom) {
-        composeDivider.setVisibility(currentlyAtBottom ? View.INVISIBLE : View.VISIBLE);
-        scrollToBottomButton.setVisibility(currentlyAtBottom ? View.INVISIBLE : View.VISIBLE);
-
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR1) {
-          composeDivider.animate().alpha(currentlyAtBottom ? 0 : 1);
-          scrollToBottomButton.animate().alpha(currentlyAtBottom ? 0 : 1);
-        } else if (Build.VERSION.SDK_INT > Build.VERSION_CODES.HONEYCOMB) {
-          composeDivider.setAlpha(currentlyAtBottom ? 0 : 1);
-          scrollToBottomButton.setAlpha(currentlyAtBottom ? 0 : 1);
-        }
-
-        wasAtBottom = currentlyAtBottom;
+      if (currentlyAtBottom && !wasAtBottom) {
+        ViewUtil.fadeOut(composeDivider, 50, View.INVISIBLE);
+        ViewUtil.animateOut(scrollToBottomButton, scrollButtonOutAnimation, View.INVISIBLE);
+      } else if (!currentlyAtBottom && wasAtBottom) {
+        ViewUtil.fadeIn(composeDivider, 500);
       }
+
+      if (currentlyAtZoomScrollHeight && !wasAtZoomScrollHeight) {
+        ViewUtil.animateIn(scrollToBottomButton, scrollButtonInAnimation);
+      }
+
+      wasAtBottom           = currentlyAtBottom;
+      wasAtZoomScrollHeight = currentlyAtZoomScrollHeight;
     }
 
     private boolean isAtBottom() {
@@ -439,6 +456,10 @@ public class ConversationFragment extends Fragment
 
       return isAtBottom && bottomView.getBottom() <= list.getHeight();
     }
+
+    private boolean isAtZoomScrollHeight() {
+      return ((LinearLayoutManager) list.getLayoutManager()).findFirstCompletelyVisibleItemPosition() > 4;
+    }
   }
 
   private class ConversationFragmentItemClickListener implements ItemClickListener {