@connected-home/react-native-fast-image

🚩 FastImage

Performant React Native image component.

FastImage 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.
• Border radius.

Usage

# Install
yarn add react-native-fast-image

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

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)
• Are you using Glide already using an AppGlideModule? (you might have problems if you don't read this)

Proguard

If you use Proguard you will need to add these lines to android/app/proguard-rules.pro:

-keep public class com.dylanvann.fastimage.* {*;}
-keep public class com.dylanvann.fastimage.** {*;}

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.

---

source.cache?: enum

• FastImage.cacheControl.immutable - (Default) - Only updates if url changes.
• FastImage.cacheControl.web - Use headers and follow normal caching procedures.
• FastImage.cacheControl.cacheOnly - Only show images from cache, do not make any network requests.

---

source.cacheOmitURLParams?: boolean

If true will be cached under url without query params Useful when image url is dynamic and query params contain security information

---

source.resize?: object

• width (required)
• height (required)

You may sometimes encouter performance issues on Android with very large images being scaled down to a small container. The best solution is to always try and request images with the appropriate size, however if you know the original image dimensions - you can use this property to set a custom width and height for the image. This will manually scale the image down before loading it into the view - giving you similar performance benefits to how React Native's resizeMethod="resize" would work on the default <Image /> component.

---

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.

---

fallback: boolean

If true will fallback to using Image. In this case the image will still be styled and laid out the same way as FastImage.

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

Follow these instructions to get the example app running.

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.

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 © DylanVann
• SDWebImage - MIT
• Glide - BSD, part MIT and Apache 2.0. See the LICENSE file for details.