From f07267bb2a4c9c7654ffeb3a50c4c7b01494cb83 Mon Sep 17 00:00:00 2001
From: vishtree <vishalnarkhede.iitd@gmail.com>
Date: Fri, 26 Feb 2021 16:56:13 +0100
Subject: [PATCH] Fixed un-necessary calls to resetMvcpIfNeeded

Fixes - https://github.com/GetStream/flat-list-mvcp/issues/6
---
 Example/App.tsx                 |  1 -
 Example/src/FlatListExample.tsx | 30 +++++++++++++++++++++---------
 src/FlatList.tsx                | 17 +++++++++++------
 3 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/Example/App.tsx b/Example/App.tsx
index 554b698..fa6b637 100644
--- a/Example/App.tsx
+++ b/Example/App.tsx
@@ -1,5 +1,4 @@
 import React from 'react';
-// eslint-disable-next-line no-unused-vars
 // eslint-disable-next-line @typescript-eslint/no-unused-vars
 import ScrollViewExample from './src/ScrollViewExample';
 import FlatListExample from './src/FlatListExample';
diff --git a/Example/src/FlatListExample.tsx b/Example/src/FlatListExample.tsx
index aa7b350..b8a0e3a 100644
--- a/Example/src/FlatListExample.tsx
+++ b/Example/src/FlatListExample.tsx
@@ -16,18 +16,28 @@ const AddMoreButton = ({onPress}) => (
 
 const ListItem = ({item}) => (
   <View style={styles.listItem}>
-    <Text>List item: {item}</Text>
+    <Text>List item: {item.value}</Text>
   </View>
 );
 
+// Generate unique key list item.
+export const generateUniqueKey = () =>
+  `_${Math.random().toString(36).substr(2, 9)}`;
+
 export default () => {
-  const [numbers, setNumbers] = useState(Array.from(Array(10).keys()));
+  const [numbers, setNumbers] = useState(
+    Array.from(Array(10).keys()).map((n) => ({
+      id: generateUniqueKey(),
+      value: n,
+    })),
+  );
 
   const addToEnd = () => {
     setNumbers((prev) => {
-      const additionalNumbers = Array.from(Array(5).keys()).map(
-        (n) => n + prev[prev.length - 1] + 1,
-      );
+      const additionalNumbers = Array.from(Array(5).keys()).map((n) => ({
+        id: generateUniqueKey(),
+        value: n + prev[prev.length - 1].value + 1,
+      }));
 
       return prev.concat(additionalNumbers);
     });
@@ -36,7 +46,10 @@ export default () => {
   const addToStart = () => {
     setNumbers((prev) => {
       const additionalNumbers = Array.from(Array(5).keys())
-        .map((n) => prev[0] - n - 1)
+        .map((n) => ({
+          id: generateUniqueKey(),
+          value: prev[0].value - n - 1,
+        }))
         .reverse();
 
       return additionalNumbers.concat(prev);
@@ -49,10 +62,9 @@ export default () => {
       <View style={styles.listContainer}>
         <FlatList
           data={numbers}
-          keyExtractor={(item) => item.toString()}
+          keyExtractor={(item) => item.id}
           maintainVisibleContentPosition={{
-            autoscrollToTopThreshold: 20,
-            minIndexForVisible: 0,
+            minIndexForVisible: 1,
           }}
           renderItem={ListItem}
         />
diff --git a/src/FlatList.tsx b/src/FlatList.tsx
index 1f79356..dd9fe8e 100644
--- a/src/FlatList.tsx
+++ b/src/FlatList.tsx
@@ -20,17 +20,23 @@ export default (React.forwardRef(
     const flRef = useRef<FlatList<T> | null>(null);
     const { maintainVisibleContentPosition: mvcp } = props;
 
-    const autoscrollToTopThreshold = useRef<number>();
+    const autoscrollToTopThreshold = useRef<number | null>();
     const minIndexForVisible = useRef<number>();
     const cleanupPromiseRef = useRef<Promise<any>>();
 
+    const getAutoscrollToTopThresholdFromProp = () =>
+      mvcp?.autoscrollToTopThreshold || -Number.MAX_SAFE_INTEGER;
+
+    const getMinIndexForVisibleFromProp = () => mvcp?.minIndexForVisible || 1;
+
     const resetMvcpIfNeeded = (): void => {
       if (!mvcp || Platform.OS !== 'android' || !flRef.current) {
         return;
       }
       if (
-        autoscrollToTopThreshold.current === mvcp.autoscrollToTopThreshold &&
-        minIndexForVisible.current === mvcp.minIndexForVisible
+        autoscrollToTopThreshold.current ===
+          getAutoscrollToTopThresholdFromProp() &&
+        minIndexForVisible.current === getMinIndexForVisibleFromProp()
       ) {
         // Don't do anythinig if the values haven't changed
         return;
@@ -41,9 +47,8 @@ export default (React.forwardRef(
           MvcpScrollViewManager.disableMaintainVisibleContentPosition(handle);
         });
 
-      autoscrollToTopThreshold.current =
-        mvcp.autoscrollToTopThreshold || -Number.MAX_SAFE_INTEGER;
-      minIndexForVisible.current = mvcp.minIndexForVisible || 0;
+      autoscrollToTopThreshold.current = getAutoscrollToTopThresholdFromProp();
+      minIndexForVisible.current = getMinIndexForVisibleFromProp();
 
       const viewTag = findNodeHandle(flRef.current);
       cleanupPromiseRef.current = MvcpScrollViewManager.enableMaintainVisibleContentPosition(