react / react/react-native

maintainVisibleContentPosition incorrectly autoscrolls on ios

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Issue: Author Provided Repro Needs: Triage :mag: Platform: iOS
Dominant language
C++
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Description

Description

What I want is for flatlist to maintain its position if the offset is larger than 10, otherwise automatically scroll to new content, so I am using the maintainVisibleContentPosition with values of { minIndexForVisible: 0, autoscrollToTopThreshold: 10, }. Now this works correctly on android but not on ios.

Here is a small reproducible or its snack:

import React, {useState} from 'react';
import {
  SafeAreaView,
  View,
  FlatList,
  StyleSheet,
  Text,
  StatusBar,
  Button,
} from 'react-native';

type ItemProps = {title: string};

const Item = ({title}: ItemProps) => (
  <View style={styles.item}>
    <Text style={styles.title}>{title}</Text>
  </View>
);

const App = () => {
  const [data, setData] = useState([1, 2, 3, 4, 5, 6, 7, 8, 9]);

  const addToTop = () => {
    setData([data[0] - 1, ...data]);
  };

  const removeFromTop = () => {
    const [_, ...rest] = data;
    setData(rest);
  };

  return (
    <SafeAreaView style={styles.container}>
      <FlatList
        maintainVisibleContentPosition={{ minIndexForVisible: 0, autoscrollToTopThreshold: 10, }}
        data={data}
        renderItem={({item}) => <Item title={`Item ${item}`} />}
        keyExtractor={item => item.toString()}
      />
      <Button title="add to top" onPress={addToTop} />
      <Button title="remove from top" onPress={removeFromTop} />
    </SafeAreaView>
  );
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
    marginTop: StatusBar.currentHeight || 0,
  },
  item: {
    backgroundColor: '#f9c2ff',
    padding: 20,
    marginVertical: 8,
    marginHorizontal: 16,
    height: 480,
  },
  title: {
    fontSize: 32,
  },
});

export default App;
Steps to reproduce
  1. Copy the repro above to some rn project
  2. Scroll to half of the first element, then press addToTop, on android position will be maintained which is correct but on ios it autoscrolls.
React Native Version

0.73.4

Affected Platforms

Runtime - iOS

Output of npx react-native info
System:
  OS: macOS 14.1.2
  CPU: (16) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
  Memory: 2.57 GB / 16.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 18.17.1
    path: ~/.nvm/versions/node/v18.17.1/bin/node
  Yarn:
    version: 1.22.19
    path: ~/.nvm/versions/node/v18.17.1/bin/yarn
  npm:
    version: 9.6.7
    path: ~/.nvm/versions/node/v18.17.1/bin/npm
  Watchman:
    version: 2024.01.22.00
    path: /usr/local/bin/watchman
Managers:
  CocoaPods:
    version: 1.15.0
    path: /Users/ramiel/.rbenv/shims/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 23.2
      - iOS 17.2
      - macOS 14.2
      - tvOS 17.2
      - visionOS 1.0
      - watchOS 10.2
  Android SDK: Not Found
IDEs:
  Android Studio: 2023.1 AI-231.9392.1.2311.11076708
  Xcode:
    version: 15.2/15C500b
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 11.0.15
    path: /usr/local/opt/openjdk@11/bin/javac
  Ruby:
    version: 2.7.6
    path: /Users/ramiel/.rbenv/shims/ruby
npmPackages:
  "@react-native-community/cli": Not Found
  react:
    installed: 18.2.0
    wanted: 18.2.0
  react-native:
    installed: 0.73.4
    wanted: 0.73.4
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: false
iOS:
  hermesEnabled: true
  newArchEnabled: false


### Stacktrace or Logs

```text
No Stacktrace or Logs
Reproducer

https://snack.expo.dev/@ramiel99/spunky-green-peanut

Screenshots and Videos

https://github.com/facebook/react-native/assets/80689446/456e98f1-d5a8-4253-9a53-9b8d08e61426

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by running the linked Snack on iOS and Android and exercise FlatList's maintainVisibleContentPosition with the add-to-top and remove-from-top actions. Trace the FlatList behavior around the reported threshold, then verify that iOS maintains the offset when it is over 10 and only autoscrolls when it is within the threshold, matching Android.

Written by the indexing model from the issue text.

Assessment

Tech stack
ios, react-native
Domain
mobile
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
42/100

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