From 04df196896fa231deae5a1e0554eef843e19882a Mon Sep 17 00:00:00 2001
From: lujun <lujun.byte@gmail.com>
Date: Sun, 27 Dec 2020 17:46:32 +0800
Subject: [PATCH] fix performance lag caused by scrollbar value set invoke

---
 .../Sources/Runtime/Scroller/Scroller.cs      | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/Assets/FancyScrollView/Sources/Runtime/Scroller/Scroller.cs b/Assets/FancyScrollView/Sources/Runtime/Scroller/Scroller.cs
index 27da6fc..39d5cf2 100644
--- a/Assets/FancyScrollView/Sources/Runtime/Scroller/Scroller.cs
+++ b/Assets/FancyScrollView/Sources/Runtime/Scroller/Scroller.cs
@@ -9,6 +9,7 @@
 using UnityEngine.EventSystems;
 using UnityEngine.UI;
 using EasingCore;
+using UnityEngine.Events;
 
 namespace FancyScrollView
 {
@@ -141,6 +142,11 @@ public float Position
                 UpdatePosition(value);
             }
         }
+        
+        /// <summary>
+        /// Scrollbar onValueChangedAction
+        /// </summary>
+        private UnityAction<float> scrollbarOnValueChangedAction;
 
         readonly AutoScrollState autoScrollState = new AutoScrollState();
 
@@ -205,7 +211,7 @@ protected override void Start()
 
             if (scrollbar)
             {
-                scrollbar.onValueChanged.AddListener(x => UpdatePosition(x * (totalCount - 1f), false));
+                scrollbarOnValueChangedAction = x => UpdatePosition(x * (totalCount - 1f), false);
             }
         }
 
@@ -472,9 +478,18 @@ void UpdatePosition(float position, bool updateScrollbar = true)
         {
             onValueChanged?.Invoke(currentPosition = position);
 
-            if (scrollbar && updateScrollbar)
+            if (!scrollbar)
+            {
+                return;
+            }
+            
+            // If 'updateScrollbar' equals 'true' means this method is called by 'Scroller', otherwise from the
+            // scrollbar drag invoke
+            if (updateScrollbar)
             {
+                scrollbar.onValueChanged.RemoveListener(scrollbarOnValueChangedAction);
                 scrollbar.value = Mathf.Clamp01(position / Mathf.Max(totalCount - 1f, 1e-4f));
+                scrollbar.onValueChanged.AddListener(scrollbarOnValueChangedAction);
             }
         }