react-native-shared-element

react-native-shared-element

Native shared element transition primitives for react-native 💫

WORK IN PROGRESS

Index

• react-native-shared-element
• WORK IN PROGRESS
  • Index
  • Installation
  • Basic usage
  • How it works
  • API Documentation
    • SharedElement
      • Props
    • SharedElementTransition
      • Props
    • Animations
      • SharedElementTransitionAnimation
      • SharedElementTransitionResize
      • SharedElementTransitionAlign
  • Example app
  • Todo
  • License
  • Credits

Installation

yarn add react-native-shared-element

Link the native code (TODO: Update for auto-linking)

react-native link react-native-shared-element

Basic usage

import { SharedElement, SharedElementTransition } from 'react-native-shared-element';


// Scene 1
let startNode;
<View>
  ...
  <SharedElement onNode={node => startNode = node}>
    <Image style={styles.image} source={...} />
  </SharedElement>
  ...
</View>


// Scene2
let endNode;
<View>
  ...
  <SharedElement onNode={node => endNode = node}>
    <Image style={styles.image} source={...} />
  </SharedElement>
  ...
</View>

// Render overlay in front of screen
const position = new Animated.Value(0);
<View style={StyleSheet.absoluteFill}>
  <SharedElementTransition
    start={{node: startNode}}
    end={{node: endNode}}
    position={position} />
</View>

How it works

react-native-shared-element is a "primitive" that runs shared element transitions entirely native without requiring any passes over the JavaScript bridge. It works by taking in a start- and end node, which are obtained using the <SharedElement> component.

Whenever a transition between screens occurs (e.g. performed by a router/navigator), a view in front of the app should be rendered to host the shared element transition. The position prop is used to interpolate between the start- and end nodes, 0 meaning "Show the start node" and 1 meaning "Show the end node".

Whenever the <SharedElementTransition> component is rendered, it performs the following tasks:

• Measure the size and position of the provided element
• Obtain the styles of the elements
• Obtain the visual content of the elements (e.g. an image or a view snapshot)
• Render a visual copy of the start element at its current position
• Hide the original elements whenever the visual copy are on the screen
• Monitor the position prop and render the shared element transition accordingly
• Upon unmount, unhide the original elements

You typically do not use this component directly, but instead use a Router or Transition-engine which provides a higher-level API. See ./Example/src/components/Router.js for an example implementation of a simple stack router using shared element transitions.

API Documentation

SharedElement

The <SharedElement> component accepts a single child and returns a node to it through the onNode event handler. The child must be a "real" View which exists in the native view hierarchy.

Props

Property	Type	Description
children	element	A single child component, which must map to a real view in the native view hierarchy
onNode	function	Event handler that sets or unsets the node-handle
View props...		Other props supported by View

SharedElementTransition

The <SharedElementTransition> component executes a shared element transition natively. It natively performs the following tasks: measure, clone, hide, animate and unhide, to achieve the best results.

Props

Property	Type	Description
start	{ node: SharedElementNode, ancestor: SharedElementNode }	Start node- and ancestor
end	{ node: SharedElementNode, ancestor: SharedElementNode }	End node- and ancestor
position	`number	Animated.Value`
animation	SharedElementTransitionAnimation	Type of animation, e.g move start element or cross-fade between start- and end elements (default = move)
resize	SharedElementTransitionResize	Resize behavior (default = stretch)
align	SharedElementTransitionAlign	Alignment behavior (default = center-center)
debug	boolean	Renders debug overlays for diagnosing measuring and animations
onMeasure	function	Event handler that is called when nodes have been measured and snapshotted

Animations

The following animation-types are available.

SharedElementTransitionAnimation

Animation	Description
move	Moves the start- element to the end position
fade	Cross-fades between the start- and end elements

SharedElementTransitionResize

Resize-mode	Description
stretch	Stretches the element to the same shape and size of the other element. If the aspect-ratio of the content differs, you may see stretched. In that case consider one of the other resize options.
clip	Do not resize, but clip the content to the size of the other content. This option is for instance useful in combination with <Text> components, where you want to reveal more text.
none	Do not resize the content. When combined with fade, this creates a plain cross-fade effect without any resizing or clipping

SharedElementTransitionAlign

The following alignment options are available

left-center, left-top, left-right, right-center, right-top, right-right, center-top center-center, center-bottom

Example app

The example app is located in ./Example and serves as an exploration and testing tool. It features a simple stack router which implements the shared element primitives.

Todo

License

Shared element transition library is licensed under The MIT License.

Credits

This project is supported by amazing people from Expo.io

Changelog

0.4.0 (2019-08-28)

Initial release