feat: support for min index

steuerbot · Aug 24, 2022 · 0218c71 · 0218c71
1 parent 1dbbea3
commit 0218c71
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Showing 4 changed files with 23 additions and 15 deletions.
diff --git a/android/src/main/java/com/reactnativebidirectionalflatlist/scroll/ScrollView.java b/android/src/main/java/com/reactnativebidirectionalflatlist/scroll/ScrollView.java
@@ -38,10 +38,11 @@ public void setShiftOffset(double shiftOffset) {
   @Override
   public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft, int oldTop, int oldRight, int oldBottom) {
     super.onLayoutChange(v, left, top, right, bottom, oldLeft, oldTop, oldRight, oldBottom);
+    int shiftHeight = Math.min(bottom - oldBottom, (int)mShiftHeight);
     int scrollWindowHeight = getHeight() - getPaddingBottom() - getPaddingTop();
-    if(mShiftHeight != 0 && mShiftOffset <= getScrollY() + scrollWindowHeight / 2) {
+    if(mShiftHeight != 0 && shiftHeight > 0 && mShiftOffset <= getScrollY() + scrollWindowHeight / 2) {
       // correct
-      scrollTo(0, getScrollY() + (int)mShiftHeight);
+      scrollTo(0, getScrollY() + shiftHeight);
       if(getOverScrollerFromParent() != null && !getOverScrollerFromParent().isFinished()) {
         // get current directed velocity from scroller
         int direction = getOverScrollerFromParent().getFinalY() - getOverScrollerFromParent().getStartY() > 0 ? 1 : -1;

diff --git a/src/FlatList.tsx b/src/FlatList.tsx
@@ -3,8 +3,9 @@ import { FlatList as FlatListRN, LayoutChangeEvent, Platform, ScrollViewProps, S
 import { ScrollView } from './ScrollView';
 import { usePrerenderedData } from './hooks/usePrerenderedData';
 import type { BidirectionalFlatListProps, FlatListType } from './types';
+import { MIN_INDEX } from './config';
 
-const maintainVisibleContentPosition = { minIndexForVisible: 1 };
+const maintainVisibleContentPosition = { minIndexForVisible: MIN_INDEX };
 
 const FlatListImpl = forwardRef<FlatListType, BidirectionalFlatListProps>((props, ref) => {
   const renderScrollComponent = useCallback((props: ScrollViewProps) => {

diff --git a/src/config.ts b/src/config.ts
@@ -0,0 +1 @@
+export const MIN_INDEX = 1;
diff --git a/src/hooks/usePrerenderedData.tsx b/src/hooks/usePrerenderedData.tsx
@@ -1,6 +1,7 @@
 import React, { MutableRefObject, ReactNode, useCallback, useEffect, useRef, useState } from 'react';
 import { FlatListProps, LayoutChangeEvent, View } from 'react-native';
 import type { FlatListType, OnUpdateData, RenderItem } from '../types';
+import { MIN_INDEX } from '../config';
 
 type OnLayout = (options: {id: string; height: number}) => void;
 
@@ -41,13 +42,15 @@ export const usePrerenderedData = ({data, keyExtractor, renderItem, scrollRef, o
         return p;
       }, {});
       const index = data.findIndex((d) => d === newD[0]);
-      const shift = {
-        height: newD.reduce((p, c, i) => p + heightsRef.current[keyExtractor(c, i)], 0),
-        offset: data.slice(0, index).reduce((p, c, i) => p + heightsRef.current[keyExtractor(c, i)], 0),
-      };
-      scrollRef.current?.shift(shift);
+      if(index > 0 && index <= MIN_INDEX) {
+        const shift = {
+          height: newD.reduce((p, c, i) => p + heightsRef.current[keyExtractor(c, i)], 0),
+          offset: data.slice(0, index).reduce((p, c, i) => p + heightsRef.current[keyExtractor(c, i)], 0),
+        };
+        scrollRef.current?.shift(shift);
+        onUpdateData?.({heights: heightsRef.current, ...shift});
+      }
       setFinalData(data);
-      onUpdateData?.({heights: heightsRef.current, ...shift});
       return;
     }
     setNewData(data.filter((d, i) => !heightsRef.current[keyExtractor(d, i)]));
@@ -67,14 +70,16 @@ export const usePrerenderedData = ({data, keyExtractor, renderItem, scrollRef, o
       return;
     }
     const index = data.findIndex((d) => d === newData[0]);
-    const shift = {
-      height: newData.reduce((p, c, i) => p + heightsRef.current[keyExtractor(c, i)], 0),
-      offset: data.slice(0, index).reduce((p, c, i) => p + heightsRef.current[keyExtractor(c, i)], 0),
-    };
-    scrollRef.current?.shift(shift);
+    if(index > 0 && index <= MIN_INDEX) {
+      const shift = {
+        height: newData.reduce((p, c, i) => p + heightsRef.current[keyExtractor(c, i)], 0),
+        offset: data.slice(0, index).reduce((p, c, i) => p + heightsRef.current[keyExtractor(c, i)], 0),
+      };
+      scrollRef.current?.shift(shift);
+      onUpdateData?.({heights: heightsRef.current, ...shift});
+    }
     setNewData([]);
     setFinalData(data);
-    onUpdateData?.({heights: heightsRef.current, ...shift});
   }, [data, keyExtractor, newData, onUpdateData, scrollRef]);
 
   return {