From 65cb0d2def613eeb7e4b3736675d65264e7216c9 Mon Sep 17 00:00:00 2001
From: Lukasz Stanislawski <l.stanislaws@samsung.com>
Date: Mon, 21 Dec 2020 14:36:57 +0100
Subject: [PATCH] Add Appearing/Disappearing events

Handle Disappearing in ExercisePreviewView to stop player.
---
 Fitness/Controls/NavigationStack.cs  |  4 +++
 Fitness/Controls/Page.cs             | 47 ++++++++++++++++++++++++++++++------
 Fitness/Views/ExercisePreviewView.cs | 20 +++++----------
 3 files changed, 49 insertions(+), 22 deletions(-)

diff --git a/Fitness/Controls/NavigationStack.cs b/Fitness/Controls/NavigationStack.cs
index 41b0724..9126ab3 100644
--- a/Fitness/Controls/NavigationStack.cs
+++ b/Fitness/Controls/NavigationStack.cs
@@ -27,11 +27,13 @@ namespace Fitness.Controls
             if (pages.TryPeek(out Page last))
             {
                 last.ConnectedPage = page;
+                last.InvokeDisappearing();
             }
 
             page.ConnectedPage = last;
             Add(page);
             pages.Push(page);
+            page.InvokeAppearing();
         }
 
         public void Pop()
@@ -54,6 +56,7 @@ namespace Fitness.Controls
         {
             if (pages.TryPeek(out Page last))
             {
+                last.InvokeDisappearing();
                 Remove(last);
                 pages.Pop();
             }
@@ -63,6 +66,7 @@ namespace Fitness.Controls
         {
             if (pages.TryPeek(out Page current))
             {
+                current.InvokeAppearing();
                 current.Show();
             }
         }
diff --git a/Fitness/Controls/Page.cs b/Fitness/Controls/Page.cs
index fea2ced..02385d6 100644
--- a/Fitness/Controls/Page.cs
+++ b/Fitness/Controls/Page.cs
@@ -18,6 +18,17 @@ namespace Fitness.Controls
             HeightResizePolicy = ResizePolicyType.FillToParent;
         }
 
+        /// <summary>
+        /// An event triggered when page is brought to foreground.
+        /// </summary>
+        public event EventHandler Appearing;
+
+        /// <summary>
+        /// An event triggered when page is being hidden - eg. removed from
+        /// stack or covered with another page.
+        /// </summary>
+        public event EventHandler Disappearing;
+
         public PageTransitionCollection PageTransitions { get; set; }
 
         internal Page ConnectedPage { get; set; }
@@ -27,14 +38,6 @@ namespace Fitness.Controls
             return ConnectedPage?.BuildConnectedAnimationContext();
         }
 
-        public virtual void OnTransitionStarted()
-        {
-        }
-
-        public virtual void OnTransitionEnded()
-        {
-        }
-
         internal ConnectedAnimationsContext BuildConnectedAnimationContext()
         {
             var context = new ConnectedAnimationsContext();
@@ -67,6 +70,34 @@ namespace Fitness.Controls
             }
         }
 
+        internal void InvokeAppearing()
+        {
+            OnAppearing();
+            Appearing?.Invoke(this, null);
+        }
+
+        internal void InvokeDisappearing()
+        {
+            OnDisappearing();
+            Disappearing?.Invoke(this, null);
+        }
+
+        protected virtual void OnTransitionStarted()
+        {
+        }
+
+        protected virtual void OnTransitionEnded()
+        {
+        }
+
+        protected virtual void OnAppearing()
+        {
+        }
+
+        protected virtual void OnDisappearing()
+        {
+        }
+
         private void TransitionsFinished(object o, EventArgs args)
         {
             PageTransitions.TransitionFinished -= TransitionsFinished;
diff --git a/Fitness/Views/ExercisePreviewView.cs b/Fitness/Views/ExercisePreviewView.cs
index 424c6f8..9cdd297 100644
--- a/Fitness/Views/ExercisePreviewView.cs
+++ b/Fitness/Views/ExercisePreviewView.cs
@@ -18,7 +18,7 @@ namespace Fitness.Views
             InitializeCallbacks();
         }
 
-        public override void OnTransitionEnded()
+        protected override void OnTransitionEnded()
         {
             CreateVideoUrlBinding();
 
@@ -27,9 +27,13 @@ namespace Fitness.Views
             this.temp.Hide();
         }
 
+        protected override void OnDisappearing()
+        {
+            this.player.Stop();
+        }
+
         private void InitializeCallbacks()
         {
-            this.VisibilityChanged += PageVisibilityChanged;
             this.reviewButton.Clicked += ReplyVideo;
             this.nextButton.Clicked += ReplyVideo;
             this.previousButton.Clicked += ReplyVideo;
@@ -54,18 +58,6 @@ namespace Fitness.Views
             this.player.SetBinding(VideoView.ResourceUrlProperty, binding);
         }
 
-        private void PageVisibilityChanged(object sender, VisibilityChangedEventArgs args)
-        {
-            if (args.Visibility == true)
-            {
-                this.player.Play();
-            }
-            else
-            {
-                this.player.Stop();
-            }
-        }
-
         private void ReplyVideo(object sender, EventArgs args)
         {
             this.player.Stop();
-- 
2.7.4