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React Native Flatlist: Benefits, How to Use, Techniques [With Examples]

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1st Jun, 2023
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React Native Flatlist: Benefits, How to Use, Techniques [With Examples]

Introduction to React Native Flatlist

React Native FlatList is a component of the React Native framework that allows developers to render large lists of data on mobile devices efficiently. It optimises performance and memory usage by rendering only the currently visible items on the screen rather than the entire list.

The FlatList React Native component provides a flexible and customisable way to display a scrollable list of data. It accepts an array of data as input and renders each item in the list using a specified renderItem function. This function defines the appearance of each item based on the data it receives.

Why Use Flatlist in React Native?

FlatList is a crucial component in React Native for efficiently rendering large data lists. Here’s why it is commonly used:

1. Performance

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FlatList in React Native is designed for optimal performance, utilising virtualisation techniques to render only the visible items on the screen. This results in improved memory usage and rendering speed, making it ideal for handling extensive data sets without sacrificing performance.

2. Memory Efficiency

FlatList minimises the memory footprint by rendering only the visible items and recycling off-screen items. This is particularly advantageous when dealing with long lists or dynamically changing data, as it ensures smooth scrolling and efficient memory management.

3. Flexibility and Customissation

FlatList offers extensive customisation options such as- defining the appearance of each item, configuring grid layouts, implementing infinite scrolling, and adding section headers and footers. This flexibility allows developers to adapt the list’s appearance and behaviour to match their requirements.

4. Integration 

FlatList seamlessly integrates with other React Native components and APIs. It can be used alongside touchable components, navigation libraries, and UI frameworks, enabling easy integration with existing projects and enhancing the overall development experience.

5. Cross-Platform Compatibility

React Native allows for building applications for both iOS and Android platforms. FlatList is a cross-platform component, ensuring consistent and efficient list rendering across different operating systems.

How to Install FlatList in React Native?

Here’s a step-by-step explanation of how to install a FlatList in React Native project:

  1. Make sure you have a React Native project set up or create a new one if needed.
  2. Open your project directory in a terminal.
  3. Run the command `npm install react-native` to install the React Native package.
  4. Run the command `npm install react-native-flatlist` to install the FlatList package.
  5. Link the package to your project by running the command `react-native link react-native-flatlist`.
  6. Rebuild your project using either `react-native run-android` for Android or `react-native run-ios` for iOS. This will apply the changes and launch your project on a simulator or device.
  7. Once the installation is complete, you can import the FlatList component into your desired React Native file.
  8. Start using FlatList in your component by creating a FlatList element and specifying the necessary props such as `data`, `renderItem`, and `keyExtractor`.

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Flatlist Props: Explained with Examples

While you can gain a fair understanding of FlatList props with examples and definitions, you certainly must look for an opportunity to explore the domain under specialised guidance. Check out the Executive PG Programme in Full Stack Development from IIITB brought to you by upGrad to help you learn more about React Native and other Full Stack Development applications.

Here are some commonly used props of the FlatList React Native, along with their explanations and example usage: 

  1. data: An array of data objects to be rendered.
  2. renderItem: A callback function that renders each item in the data array.
  3. keyExtractor: A function that extracts a unique key for each item.
  4. ItemSeparatorComponent: A component that renders a separator between items.
  5. ListHeaderComponent: A component rendered at the top of the list.
  6. ListFooterComponent: A component rendered at the bottom of the list.
  7. onRefresh: A callback function triggered when the list is pulled to refresh.
  8. refreshing: A boolean value indicating whether the list is currently refreshing.

Here’s an example of using some of the FlatList props:

Flatlist Props

This example has an array of data objects with `id` and `name` properties. The `FlatList` component renders each item using the `renderItem` callback, which displays the item’s name in a `Text` component wrapped in a `View`. The `keyExtractor` prop ensures each item has a unique key extracted from its `id`. The `ItemSeparatorComponent` prop adds a grey horizontal line between items using a `View` component with a height of 1 and a grey background. 

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Rendering Data Using Flatlist

Here’s how to render data using FlatList:

1. Create an array of data objects

Prepare an array of data objects you want to render in the list. Each object should represent an item and contain the necessary properties for rendering.

  1. Provide data to FlatList

Pass the data array as the `data` prop to the FlatList component. This provides the data to be rendered in the list.

  1. Define renderItem callback

Specify a `renderItem` prop for the FlatList component. This callback function is responsible for rendering each item in the list. It receives an object containing the item’s data and index and returns a React element representing its appearance.

  1. Customise item rendering

Within the `renderItem` callback, customise how each item is rendered based on the data provided. You can use any valid React Native components, styles, or additional logic to define the appearance and layout of each item.

  1. Key extraction

Optionally, use the `keyExtractor` prop to define a unique key for each item. This helps React Native efficiently update and re-render the list when changes occur. The keyExtractor function receives an item from the data array and should return a unique identifier for that item.

Flatlist Performance Optimisation Techniques

To optimise the performance of React Native FlatList, you can apply the following techniques:

  1. Use the `keyExtractor` prop to ensure each item in the data array has a unique key. This helps React Native efficiently update and re-render the list when changes occur
  2. Implement item rendering optimisation using PureComponent (for class components) or memo (for functional components) for the item components rendered by FlatList. These optimise rendering by implementing shallow equality checks on the item props, preventing unnecessary re-renders.
  3. Employ windowing or virtualisation techniques to render only the visible items on the screen, especially for long lists. This improves rendering speed and memory efficiency. Libraries like `react-window` or `react-native-largelist-v3` can help with windowing.
  4. Consider debouncing or throttling event handlers to limit the frequency of event triggers, preventing excessive re-renders and improving overall performance.
  5. Optimise item rendering logic by minimising the number of nested components, optimising styles, and avoiding unnecessary operations or calculations within the renderItem callback.

Applying these performance optimisation techniques, one can enhance the efficiency and responsiveness of FlatList in rendering large lists of data in React Native applications.  

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Flatlist with Pagination: Implementation Guide

Implementing pagination with FlatList in React Native involves managing the data, handling scroll events, and updating the list dynamically. To implement pagination with FlatList in React Native, follow these steps:

  1. Set up initial data and a page counter.
  2. Render the FlatList component with the initial data.
  3. Attach an onEndReached event handler to fetch the next page’s data.
  4. Update the data array and increment the page counter in the event handler.
  5. Use a loading indicator to show the loading state while fetching data.
  6. Conditionally render the loading indicator based on the loading state.
  7. Handle errors and edge cases appropriately for a smooth pagination experience.

Flatlist vs Listview: Differences and Similarities

Here’s a comparison between FlatList and ListView in React Native:

Flatlist vs Listview

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FlatList and ListView are used for rendering data lists in React Native applications. However, FlatList offers better performance, supports dynamic rendering of large data sets, and provides more flexibility for customisation. 

ListView, on the other hand, has been deprecated and is no longer actively maintained by the React Native community. Therefore, it is advisable to use FlatList for new projects or when upgrading existing ListView implementations.

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Conclusion

The FlatList component in React Native provides a powerful and efficient way to render large data lists. With its virtualisation techniques and built-in optimisations, FlatList is a valuable tool for enhancing the user experience in mobile app development.

If you want to learn more about React Native and further your understanding in the domain of Full Stack Development with an affordable yet state-of-the-art learning platform, check out the Full Stack Software Development Bootcamp from upGrad to assist you until your placement. 

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Pavan Vadapalli

Blog Author
Director of Engineering @ upGrad. Motivated to leverage technology to solve problems. Seasoned leader for startups and fast moving orgs. Working on solving problems of scale and long term technology strategy.

Frequently Asked Questions (FAQs)

1Can I use FlatList for small lists with a few items?

Yes, FlatList is suitable for all lists, including small ones. It optimises performance by rendering only the visible items, even if the list is small. It also offers flexibility and customisation options, making it a convenient choice for displaying lists of any size.

2 How to handle item selection in FlatList?

You can handle item selection in FlatList by adding a touch event handler to the item component rendered in the renderItem callback. Within the handler, you can update the state or perform necessary actions based on the selected item's data or index.

3What is React Native SectionList?

SectionList React Native is a component for rendering categorised lists with section headers. It offers efficient rendering and provides a straightforward way to organise and display grouped data.