/ Images

FastImage and performant React Native image component

FastImage and performant React Native image component

FastImage

FastImage, performant React Native image component.


Comparing FastImage to Image in the example app.

React Native's Image component handles image caching like browsers
for the most part.
If the server is returning proper cache control
headers for images you'll generally get the sort of built in
caching behavior you'd have in a browser.
Even so many people have noticed:

  • Flickering.
  • Cache misses.
  • Low performance loading from cache.
  • Low performance in general.

FastImage is an Image replacement that solves these issues.
FastImage is a wrapper around
SDWebImage (iOS)
and
Glide (Android).

Features

  • [x] Aggressively cache images.
  • [x] Add authorization headers.
  • [x] Prioritize images.
  • [x] Preload images.
  • [x] GIF support.
  • [x] Border radius.

Usage

# Install
yarn add react-native-fast-image

# Automatic linking. (other linking methods listed below)
react-native link
import FastImage from 'react-native-fast-image'

const YourImage = () =>
  <FastImage
    style={styles.image}
    source={{
      uri: 'https://unsplash.it/400/400?image=1',
      headers:{ Authorization: 'someAuthToken' },
      priority: FastImage.priority.normal,
    }}
    resizeMode={FastImage.resizeMode.contain}
  />

Other Linking Methods

  • Manual (might be needed if something went wrong with react-native link)
  • CocoaPods (iOS) (you may wish to use this if you are already using CocoaPods)

Properties

source?: object

Source for the remote image to load.


source.uri?: string

Remote url to load the image from. e.g. 'https://facebook.github.io/react/img/logo_og.png'.


source.headers?: object

Headers to load the image with. e.g. { Authorization: 'someAuthToken' }.


source.priority?: enum

  • FastImage.priority.low - Low Priority
  • FastImage.priority.normal (Default) - Normal Priority
  • FastImage.priority.high - High Priority

resizeMode?: enum

  • FastImage.resizeMode.contain - Scale the image uniformly (maintain the image's aspect ratio) so that both dimensions (width and height) of the image will be equal to or less than the corresponding dimension of the view (minus padding).
  • FastImage.resizeMode.cover (Default) - Scale the image uniformly (maintain the image's aspect ratio) so that both dimensions (width and height) of the image will be equal to or larger than the corresponding dimension of the view (minus padding).
  • FastImage.resizeMode.stretch - Scale width and height independently, This may change the aspect ratio of the src.
  • FastImage.resizeMode.center - Do not scale the image, keep centered.

onLoadStart?: () => void

Called when the image starts to load.


onProgress?: (event) => void

Called when the image is loading.

e.g. onProgress={e => console.log(e.nativeEvent.loaded / e.nativeEvent.total)}


onLoad?: (event) => void

Called on a successful image fetch. Called with the width and height of the loaded image.

e.g. onLoad={e => console.log(e.nativeEvent.width, e.nativeEvent.height)}


onError?: () => void

Called on an image fetching error.


onLoadEnd?: () => void

Called when the image finishes loading, whether it was successful or an error.


style

A React Native style. Supports using borderRadius.

Static Methods

FastImage.preload: (source[]) => void

Preload images to display later. e.g.

FastImage.preload([
  {
    uri: 'https://facebook.github.io/react/img/logo_og.png',
    headers: { Authorization: 'someAuthToken' },
  },
  {
    uri: 'https://facebook.github.io/react/img/logo_og.png',
    headers: { Authorization: 'someAuthToken' },
  },
])

Troubleshooting

If you have any problems using this library try the steps in troubleshooting and see if they fix it.

Development

# Install SDWebImage submodules.
git submodule update --init --recursive

# Install npm dependencies.
yarn

Developing modules for React Native is currently a mess because the packager does not support symlinks.

Both major package managers, [email protected] and yarn, do local installations by creating symlinks.

Unfortunately for now the workaround to update the example is to run:

# In the repo directory pack the module:
npm pack

# This makes a tarball like:
# react-native-fast-image-1.0.0.tgz

# Move into the example:
cd example

# Install the tarball:
npm install ../react-native-fast-image-1.0.0.tgz

To update while developing you can re-pack and reinstall the tarball.

Hopefully metro will add support for symlinks soon.

Supported React Native Versions

This project only aims to support the latest version of React Native.
This simplifies the development and the testing of the project.

If you require new features or bug fixes for older versions you can fork this project.

GitHub