react / react/react-native

ScrollView's scrollToEnd scrolls too far on android

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Component: ScrollView Issue: Author Provided Repro Platform: Android Resolution: PR Submitted
Dominant language
C++
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Avg merge
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Merged PRs (30d)
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Description

Description

ScrollView's scrollToEnd method gives different results on iOs and Android.

Expected behaviour:
ScrollView's scrollToEnd method should function consistently across platforms. Ideally The view should scroll until the bottom of the content reaches the bottom of the view.

Actual behaviour:
On iOs the view tries to scroll until the bottom of the content reaches the bottom of the view.
On Android the view tries to scroll until the bottom of the content reaches the top of the view.

This is especially annoying if you add content while the view is scrolling, as it then scrolls too far, or if you have an animation of content being added to slide in from the bottom.

Steps to reproduce
  1. Open the provided snack on Android
  2. Press the button labeled "Press me!"
  3. The view scrolls until element "Test 50" reaches the top of the screen
  4. Open the provided snack on iOs
  5. Press the button labeled "Press me!"
  6. The view scrolls until element "Test 49" reaches the bottom of the screen
React Native Version

0.76.3

Affected Platforms

Runtime - Android

Output of npx react-native info
System:
  OS: macOS 14.7
  CPU: (10) arm64 Apple M1 Pro
  Memory: 124.23 MB / 16.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 20.11.1
    path: ~/.nvm/versions/node/v20.11.1/bin/node
  Yarn:
    version: 1.22.19
    path: /opt/homebrew/bin/yarn
  npm:
    version: 10.2.4
    path: ~/.nvm/versions/node/v20.11.1/bin/npm
  Watchman:
    version: 2024.09.16.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.15.2
    path: /opt/homebrew/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.1
      - iOS 18.1
      - macOS 15.1
      - tvOS 18.1
      - visionOS 2.1
      - watchOS 11.1
  Android SDK: Not Found
IDEs:
  Android Studio: 2024.2 AI-242.23339.11.2421.12550806
  Xcode:
    version: 16.1/16B40
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 18.0.2.1
    path: /Users/chriscoerdes/.jenv/shims/javac
  Ruby:
    version: 2.6.10
    path: /usr/bin/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 15.0.1
    wanted: 15.0.1
  react:
    installed: 18.3.1
    wanted: 18.3.1
  react-native:
    installed: 0.76.3
    wanted: 0.76.3
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true
Stacktrace or Logs
N/A
Reproducer

https://github.com/coerdes-chris/react-native-scrollview

Screenshots and Videos

https://github.com/user-attachments/assets/ad2a0bcd-4c59-4291-8891-9f2dfbd1d13f

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 with the supplied reproducer and the Android implementation of ScrollView's scrollToEnd, then compare its behavior with the iOS result described in the issue. Verify the behavior around content added during scrolling. Done means Android stops with the content bottom aligned to the view bottom, consistently with iOS, with regression coverage if the existing test structure supports it.

Written by the indexing model from the issue text.

Assessment

Tech stack
android, react-native
Domain
mobile-dev
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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