README.md

@irisjae/flash-list

How to use

This package is on npm. @irisjae/flash-list should be compatible with @shopify/flash-list, and one should be able to simply swap it out with this instead. Lists without the preserveVisiblePosition prop passed should essentially behave identically as @shopify/flash-list. Another method to swap @shopify/flash-list for this package without having to replace imports/requires is to replace the @shopify/flash-list version in package.json with npm:@irisjae/flash-list@1.0.2.

This patch to FlashList primarily adds the preserveVisiblePosition prop to FlashList. This prop keeps the visible region of the list fixed regardless of changes in the height of items around the region and adding new data to the list.

This patch adds the preserveVisiblePosition, edgeVisibleThreshold, startEdgePreserved, shiftPreservedLayouts props. nonDeterministicMode is automatically set to "autolayout" whenever preserveVisiblePosition is used. This patch also implements the relative layouting algorithm and the onAutoLayout events of @irisjae/recyclerlistview. For more information, please see here.

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Beneath the following line one finds the original README unmodified.

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Website • Discord • Getting started • Usage • Performance • Writing performant components • Known Issues

Fast & performant React Native list. No more blank cells.

Swap from FlatList in seconds. Get instant performance.

Installation

Add the package to your project via yarn add @shopify/flash-list and run pod install in the ios directory.

Usage

We recommend reading the detailed documentation for using FlashList here.

But if you are familiar with FlatList, you already know how to use FlashList. You can try out FlashList by changing the component name and adding the estimatedItemSize prop or refer to the example below:

import React from "react";
import { View, Text } from "react-native";
import { FlashList } from "@shopify/flash-list";

const DATA = [
  {
    title: "First Item",
  },
  {
    title: "Second Item",
  },
];

const MyList = () => {
  return (
    <FlashList
      data={DATA}
      renderItem={({ item }) => <Text>{item.title}</Text>}
      estimatedItemSize={200}
    />
  );
};

To avoid common pitfalls, you can also follow these steps for migrating from FlatList, based on our own experiences:

1. Switch from FlatList to FlashList and render the list once. You should see a warning about missing estimatedItemSize and a suggestion. Set this value as the prop directly.
2. Important: Scan your renderItem hierarchy for explicit key prop definitions and remove them. If you’re doing a .map() use indices as keys.
3. Check your renderItem hierarchy for components that make use of useState and verify whether that state would need to be reset if a different item is passed to that component (see Recycling)
4. If your list has heterogenous views, pass their types to FlashList using getItemType prop to improve performance.
5. Do not test performance with JS dev mode on. Make sure you’re in release mode. FlashList can appear slower while in dev mode due to a small render buffer.

App / Playground

The fixture is an example app showing how to use the library.