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

• Aggressively cache images.
• Add authorization headers.
• Prioritize images.
• Preload images.
• GIF support.

Usage

yarn add react-native-fast-image
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}
  />

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 (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 less than the corresponding dimension of the view (minus padding).
• FastImage.resizeMode.cover - 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?: () => void

Called on a successful image fetch.

---

onError?: () => void

Called on an image fetching error.

---

onLoadEnd?: () => void

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

---

children

FastImage does not currently support children. Absolute positioning can be used as an alternative.

This is because FastImage supplies a android.widget.imageview and not a android.view.viewgroup.

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' },
  },
])

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, npm@5 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.

Credits

The idea for this modules came from vovkasm's react-native-web-image package. It also uses Glide and SDWebImage, but didn't have some features I needed (priority, headers).

Licenses

• FastImage [MIT]
• SDWebImage (included) [MIT]
• Glide (included via gradle) [Apache 2.0 License]