From e6aa39659fc1b9060aaf8d74a744e74460c6f831 Mon Sep 17 00:00:00 2001
From: serso <se.solovyev@gmail.com>
Date: Mon, 24 Jul 2017 12:10:47 +0200
Subject: [PATCH] Make FAB appear again after it has been hidden

---
 .../calculator/view/PagerViewFabBehavior.java | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/app/src/main/java/org/solovyev/android/calculator/view/PagerViewFabBehavior.java b/app/src/main/java/org/solovyev/android/calculator/view/PagerViewFabBehavior.java
index ac734aae..d13d0ed9 100644
--- a/app/src/main/java/org/solovyev/android/calculator/view/PagerViewFabBehavior.java
+++ b/app/src/main/java/org/solovyev/android/calculator/view/PagerViewFabBehavior.java
@@ -1,6 +1,7 @@
 package org.solovyev.android.calculator.view;
 
 import android.content.Context;
+import android.support.annotation.NonNull;
 import android.support.design.widget.CoordinatorLayout;
 import android.support.design.widget.FloatingActionButton;
 import android.support.v4.view.ViewCompat;
@@ -11,6 +12,18 @@ import android.view.View;
 
 public class PagerViewFabBehavior extends FloatingActionButton.Behavior {
 
+    @NonNull
+    private final FloatingActionButton.OnVisibilityChangedListener
+            visibilityListener = new FloatingActionButton.OnVisibilityChangedListener() {
+                @Override
+                public void onHidden(FloatingActionButton fab) {
+                    // by default, FloatingActionButton#hide causes FAB to be GONE which blocks any
+                    // consequent scroll updates in CoordinatorLayout#onNestedScroll. Let's make the
+                    // FAB invisible instead
+                    fab.setVisibility(View.INVISIBLE);
+                }
+            };
+
     public PagerViewFabBehavior() {
         super();
     }
@@ -49,13 +62,13 @@ public class PagerViewFabBehavior extends FloatingActionButton.Behavior {
 
     private boolean onScroll(FloatingActionButton child, float scrollX, float scrollY) {
         if (scrollY > 0 && child.getVisibility() == View.VISIBLE) {
-            child.hide();
+            child.hide(visibilityListener);
             return true;
         } else if (scrollY < 0 && child.getVisibility() != View.VISIBLE) {
-            child.show();
+            child.show(visibilityListener);
             return true;
         } else if (scrollX != 0 && child.getVisibility() != View.VISIBLE) {
-            child.show();
+            child.show(visibilityListener);
             return true;
         }
         return false;