635 lines
24 KiB
Markdown
635 lines
24 KiB
Markdown
---
|
|
id: animations
|
|
title: Animations
|
|
layout: docs
|
|
category: Guides
|
|
permalink: docs/animations.html
|
|
next: accessibility
|
|
---
|
|
|
|
Fluid, meaningful animations are essential to the mobile user experience. Like
|
|
everything in React Native, Animation APIs for React Native are currently under
|
|
development, but have started to coalesce around two complementary systems:
|
|
`LayoutAnimation` for animated global layout transactions, and `Animated` for
|
|
more granular and interactive control of specific values.
|
|
|
|
### Animated ###
|
|
|
|
The `Animated` library is designed to make it very easy to concisely express a
|
|
wide variety of interesting animation and interaction patterns in a very
|
|
performant way. `Animated` focuses on declarative relationships between inputs
|
|
and outputs, with configurable transforms in between, and simple `start`/`stop`
|
|
methods to control time-based animation execution. For example, a complete
|
|
component with a simple spring bounce on mount looks like this:
|
|
|
|
```javascript
|
|
class Playground extends React.Component {
|
|
constructor(props: any) {
|
|
super(props);
|
|
this.state = {
|
|
bounceValue: new Animated.Value(0),
|
|
};
|
|
}
|
|
render(): ReactElement {
|
|
return (
|
|
<Animated.Image // Base: Image, Text, View
|
|
source={{uri: 'http://i.imgur.com/XMKOH81.jpg'}}
|
|
style={{
|
|
flex: 1,
|
|
transform: [ // `transform` is an ordered array
|
|
{scale: this.state.bounceValue}, // Map `bounceValue` to `scale`
|
|
]
|
|
}}
|
|
/>
|
|
);
|
|
}
|
|
componentDidMount() {
|
|
this.state.bounceValue.setValue(1.5); // Start large
|
|
Animated.spring( // Base: spring, decay, timing
|
|
this.state.bounceValue, // Animate `bounceValue`
|
|
{
|
|
toValue: 0.8, // Animate to smaller size
|
|
friction: 1, // Bouncier spring
|
|
}
|
|
).start(); // Start the animation
|
|
}
|
|
}
|
|
```
|
|
|
|
`bounceValue` is initialized as part of `state` in the constructor, and mapped
|
|
to the scale transform on the image. Behind the scenes, the numeric value is
|
|
extracted and used to set scale. When the component mounts, the scale is set to
|
|
1.5 and then a spring animation is started on `bounceValue` which will update
|
|
all of its dependent mappings on each frame as the spring animates (in this
|
|
case, just the scale). This is done in an optimized way that is faster than
|
|
calling `setState` and re-rendering. Because the entire configuration is
|
|
declarative, we will be able to implement further optimizations that serialize
|
|
the configuration and runs the animation on a high-priority thread.
|
|
|
|
#### Core API
|
|
|
|
Most everything you need hangs directly off the `Animated` module. This
|
|
includes two value types, `Value` for single values and `ValueXY` for vectors,
|
|
three animation types, `spring`, `decay`, and `timing`, and three component
|
|
types, `View`, `Text`, and `Image`. You can make any other component animated with
|
|
`Animated.createAnimatedComponent`.
|
|
|
|
The three animation types can be used to create almost any animation curve you
|
|
want because each can be customized:
|
|
|
|
* `spring`: Simple single-spring physics model that matches [Origami](https://facebook.github.io/origami/).
|
|
* `friction`: Controls "bounciness"/overshoot. Default 7.
|
|
* `tension`: Controls speed. Default 40.
|
|
* `decay`: Starts with an initial velocity and gradually slows to a stop.
|
|
* `velocity`: Initial velocity. Required.
|
|
* `deceleration`: Rate of decay. Default 0.997.
|
|
* `timing`: Maps time range to easing value.
|
|
* `duration`: Length of animation (milliseconds). Default 500.
|
|
* `easing`: Easing function to define curve. See `Easing` module for several
|
|
predefined functions. iOS default is `Easing.inOut(Easing.ease)`.
|
|
* `delay`: Start the animation after delay (milliseconds). Default 0.
|
|
|
|
Animations are started by calling `start`. `start` takes a completion callback
|
|
that will be called when the animation is done. If the animation is done
|
|
because it finished running normally, the completion callback will be invoked
|
|
with `{finished: true}`, but if the animation is done because `stop` was called
|
|
on it before it could finish (e.g. because it was interrupted by a gesture or
|
|
another animation), then it will receive `{finished: false}`.
|
|
|
|
#### Composing Animations
|
|
|
|
Animations can also be composed with `parallel`, `sequence`, `stagger`, and
|
|
`delay`, each of which simply take an array of animations to execute and
|
|
automatically calls start/stop as appropriate. For example:
|
|
|
|
```javascript
|
|
Animated.sequence([ // spring to start and twirl after decay finishes
|
|
Animated.decay(position, { // coast to a stop
|
|
velocity: {x: gestureState.vx, y: gestureState.vy}, // velocity from gesture release
|
|
deceleration: 0.997,
|
|
}),
|
|
Animated.parallel([ // after decay, in parallel:
|
|
Animated.spring(position, {
|
|
toValue: {x: 0, y: 0} // return to start
|
|
}),
|
|
Animated.timing(twirl, { // and twirl
|
|
toValue: 360,
|
|
}),
|
|
]),
|
|
]).start(); // start the sequence group
|
|
```
|
|
|
|
By default, if one animation is stopped or interrupted, then all other
|
|
animations in the group are also stopped. Parallel has a `stopTogether` option
|
|
that can be set to `false` to disable this.
|
|
|
|
#### Interpolation
|
|
|
|
Another powerful part of the `Animated` API is the `interpolate` function. It
|
|
allows input ranges to map to different output ranges. For example, a simple
|
|
mapping to convert a 0-1 range to a 0-100 range would be
|
|
|
|
```javascript
|
|
value.interpolate({
|
|
inputRange: [0, 1],
|
|
outputRange: [0, 100],
|
|
});
|
|
```
|
|
|
|
`interpolate` supports multiple range segments as well, which is handy for
|
|
defining dead zones and other handy tricks. For example, to get an negation
|
|
relationship at -300 that goes to 0 at -100, then back up to 1 at 0, and then
|
|
back down to zero at 100 followed by a dead-zone that remains at 0 for
|
|
everything beyond that, you could do:
|
|
|
|
```javascript
|
|
value.interpolate({
|
|
inputRange: [-300, -100, 0, 100, 101],
|
|
outputRange: [300, 0, 1, 0, 0],
|
|
});
|
|
```
|
|
|
|
Which would map like so:
|
|
|
|
Input | Output
|
|
------|-------
|
|
-400| 450
|
|
-300| 300
|
|
-200| 150
|
|
-100| 0
|
|
-50| 0.5
|
|
0| 1
|
|
50| 0.5
|
|
100| 0
|
|
101| 0
|
|
200| 0
|
|
|
|
`interpolation` also supports arbitrary easing functions, many of which are
|
|
already implemented in the
|
|
[`Easing`](https://github.com/facebook/react-native/blob/master/Libraries/Animation/Animated/Easing.js)
|
|
class including quadradic, exponential, and bezier curves as well as functions
|
|
like step and bounce. `interpolation` also has configurable behavior for
|
|
extrapolation, the default being `'extend'`, but `'clamp'` is also very useful
|
|
to prevent the output value from exceeding `outputRange`.
|
|
|
|
#### Tracking Dynamic Values
|
|
|
|
Animated values can also track other values. Just set the `toValue` of an
|
|
animation to another animated value instead of a plain number, for example with
|
|
spring physics for an interaction like "Chat Heads", or via `timing` with
|
|
`duration: 0` for rigid/instant tracking. They can also be composed with
|
|
interpolations:
|
|
|
|
```javascript
|
|
Animated.spring(follower, {toValue: leader}).start();
|
|
Animated.timing(opacity, {
|
|
toValue: pan.x.interpolate({
|
|
inputRange: [0, 300],
|
|
outputRange: [1, 0],
|
|
}),
|
|
}).start();
|
|
```
|
|
|
|
`ValueXY` is a handy way to deal with 2D interactions, such as panning/dragging.
|
|
It is a simple wrapper that basically just contains two `Animated.Value`
|
|
instances and some helper functions that call through to them, making `ValueXY`
|
|
a drop-in replacement for `Value` in many cases. For example, in the code
|
|
snippet above, `leader` and `follower` could both be of type `ValueXY` and the x
|
|
and y values will both track as you would expect.
|
|
|
|
#### Input Events
|
|
|
|
`Animated.event` is the input side of the Animated API, allowing gestures and
|
|
other events to map directly to animated values. This is done with a structured
|
|
map syntax so that values can be extracted from complex event objects. The
|
|
first level is an array to allow mapping across multiple args, and that array
|
|
contains nested objects. In the example, you can see that `scrollX` maps to
|
|
`event.nativeEvent.contentOffset.x` (`event` is normally the first arg to the
|
|
handler), and `pan.x` and `pan.y` map to `gestureState.dx` and `gestureState.dy`,
|
|
respectively (`gestureState` is the second arg passed to the `PanResponder` handler).
|
|
|
|
```javascript
|
|
onScroll={Animated.event(
|
|
[{nativeEvent: {contentOffset: {x: scrollX}}}] // scrollX = e.nativeEvent.contentOffset.x
|
|
)}
|
|
onPanResponderMove={Animated.event([
|
|
null, // ignore the native event
|
|
{dx: pan.x, dy: pan.y} // extract dx and dy from gestureState
|
|
]);
|
|
```
|
|
|
|
#### Responding to the Current Animation Value
|
|
|
|
You may notice that there is no obvious way to read the current value while
|
|
animating - this is because the value may only be known in the native runtime
|
|
due to optimizations. If you need to run JavaScript in response to the current
|
|
value, there are two approaches:
|
|
|
|
- `spring.stopAnimation(callback)` will stop the animation and invoke `callback`
|
|
with the final value - this is useful when making gesture transitions.
|
|
- `spring.addListener(callback)` will invoke `callback` asynchronously while the
|
|
animation is running, providing a recent value. This is useful for triggering
|
|
state changes, for example snapping a bobble to a new option as the user drags
|
|
it closer, because these larger state changes are less sensitive to a few frames
|
|
of lag compared to continuous gestures like panning which need to run at 60fps.
|
|
|
|
#### Future Work
|
|
|
|
As previously mentioned, we're planning on optimizing Animated under the hood to
|
|
make it even more performant. We would also like to experiment with more
|
|
declarative and higher level gestures and triggers, such as horizontal vs.
|
|
vertical panning.
|
|
|
|
The above API gives a powerful tool for expressing all sorts of animations in a
|
|
concise, robust, and performant way. Check out more example code in
|
|
[UIExplorer/AnimationExample](https://github.com/facebook/react-native/blob/master/Examples/UIExplorer/AnimationExample). Of course there may still be times where `Animated`
|
|
doesn't support what you need, and the following sections cover other animation
|
|
systems.
|
|
|
|
### LayoutAnimation
|
|
|
|
`LayoutAnimation` allows you to globally configure `create` and `update`
|
|
animations that will be used for all views in the next render/layout cycle.
|
|
This is useful for doing flexbox layout updates without bothering to measure or
|
|
calculate specific properties in order to animate them directly, and is
|
|
especially useful when layout changes may affect ancestors, for example a "see
|
|
more" expansion that also increases the size of the parent and pushes down the
|
|
row below which would otherwise require explicit coordination between the
|
|
components in order to animate them all in sync.
|
|
|
|
Note that although `LayoutAnimation` is very powerful and can be quite useful,
|
|
it provides much less control than `Animated` and other animation libraries, so
|
|
you may need to use another approach if you can't get `LayoutAnimation` to do
|
|
what you want.
|
|
|
|
|
|
|
|
```javascript
|
|
var App = React.createClass({
|
|
componentWillMount() {
|
|
// Animate creation
|
|
LayoutAnimation.spring();
|
|
},
|
|
|
|
getInitialState() {
|
|
return { w: 100, h: 100 }
|
|
},
|
|
|
|
_onPress() {
|
|
// Animate the update
|
|
LayoutAnimation.spring();
|
|
this.setState({w: this.state.w + 15, h: this.state.h + 15})
|
|
},
|
|
|
|
render: function() {
|
|
return (
|
|
<View style={styles.container}>
|
|
<View style={[styles.box, {width: this.state.w, height: this.state.h}]} />
|
|
<TouchableOpacity onPress={this._onPress}>
|
|
<View style={styles.button}>
|
|
<Text style={styles.buttonText}>Press me!</Text>
|
|
</View>
|
|
</TouchableOpacity>
|
|
</View>
|
|
);
|
|
}
|
|
});
|
|
```
|
|
[Run this example](https://rnplay.org/apps/uaQrGQ)
|
|
|
|
This example uses a preset value, you can customize the animations as
|
|
you need, see [LayoutAnimation.js](https://github.com/facebook/react-native/blob/master/Libraries/Animation/LayoutAnimation.js)
|
|
for more information.
|
|
|
|
### requestAnimationFrame
|
|
|
|
`requestAnimationFrame` is a polyfill from the browser that you might be
|
|
familiar with. It accepts a function as its only argument and calls that
|
|
function before the next repaint. It is an essential building block for
|
|
animations that underlies all of the JavaScript-based animation APIs. In
|
|
general, you shouldn't need to call this yourself - the animation API's will
|
|
manage frame updates for you.
|
|
|
|
### react-tween-state (Not recommended - use [Animated](#animated) instead)
|
|
|
|
[react-tween-state](https://github.com/chenglou/react-tween-state) is a
|
|
minimal library that does exactly what its name suggests: it *tweens* a
|
|
value in a component's state, starting at a **from** value and ending at
|
|
a **to** value. This means that it generates the values in between those
|
|
two values, and it sets the state on every `requestAnimationFrame` with
|
|
the intermediary value.
|
|
|
|
> Tweening definition from [Wikipedia](https://en.wikipedia.org/wiki/Inbetweening)
|
|
>
|
|
> "... tweening is the process of generating intermediate frames between two
|
|
> images to give the appearance that the first image evolves smoothly
|
|
> into the second image. [Tweens] are the drawings between the key
|
|
> frames which help to create the illusion of motion."
|
|
|
|
The most obvious way to animate from one value to another is linearly:
|
|
you subtract the end value from the start value and divide the result by
|
|
the number of frames over which the animation occurs, and then add that
|
|
value to the current value on each frame until the end value is reached.
|
|
Linear easing often looks awkward and unnatural, so react-tween-state
|
|
provides a selection of popular [easing functions](http://easings.net/)
|
|
that can be applied to make your animations more pleasing.
|
|
|
|
This library does not ship with React Native - in order to use it on
|
|
your project, you will need to install it with `npm i react-tween-state
|
|
--save` from your project directory.
|
|
|
|
```javascript
|
|
var tweenState = require('react-tween-state');
|
|
|
|
var App = React.createClass({
|
|
mixins: [tweenState.Mixin],
|
|
|
|
getInitialState() {
|
|
return { opacity: 1 }
|
|
},
|
|
|
|
_animateOpacity() {
|
|
this.tweenState('opacity', {
|
|
easing: tweenState.easingTypes.easeOutQuint,
|
|
duration: 1000,
|
|
endValue: this.state.opacity === 0.2 ? 1 : 0.2,
|
|
});
|
|
},
|
|
|
|
render() {
|
|
return (
|
|
<View style={{flex: 1, justifyContent: 'center', alignItems: 'center'}}>
|
|
<TouchableWithoutFeedback onPress={this._animateOpacity}>
|
|
<View ref={component => this._box = component}
|
|
style={{width: 200, height: 200, backgroundColor: 'red',
|
|
opacity: this.getTweeningValue('opacity')}} />
|
|
</TouchableWithoutFeedback>
|
|
</View>
|
|
)
|
|
},
|
|
});
|
|
```
|
|
[Run this example](https://rnplay.org/apps/4FUQ-A)
|
|
|
|
|
|
|
|
Here we animated the opacity, but as you might guess, we can animate any
|
|
numeric value. Read more about react-tween-state in its
|
|
[README](https://github.com/chenglou/react-tween-state).
|
|
|
|
### Rebound (Not recommended - use [Animated](#animated) instead)
|
|
|
|
[Rebound.js](https://github.com/facebook/rebound-js) is a JavaScript port of
|
|
[Rebound for Android](https://github.com/facebook/rebound). It is
|
|
similar in concept to react-tween-state: you have an initial value and
|
|
set an end value, then Rebound generates intermediate values that you can
|
|
use for your animation. Rebound is modeled after spring physics; we
|
|
don't provide a duration when animating with springs, it is
|
|
calculated for us depending on the spring tension, friction, current
|
|
value and end value. Rebound [is used
|
|
internally](https://github.com/facebook/react-native/search?utf8=%E2%9C%93&q=rebound)
|
|
by React Native on `Navigator` and `WarningBox`.
|
|
|
|
|
|
|
|
Notice that Rebound animations can be interrupted - if you release in
|
|
the middle of a press, it will animate back from the current state to
|
|
the original value.
|
|
|
|
```javascript
|
|
var rebound = require('rebound');
|
|
|
|
var App = React.createClass({
|
|
// First we initialize the spring and add a listener, which calls
|
|
// setState whenever it updates
|
|
componentWillMount() {
|
|
// Initialize the spring that will drive animations
|
|
this.springSystem = new rebound.SpringSystem();
|
|
this._scrollSpring = this.springSystem.createSpring();
|
|
var springConfig = this._scrollSpring.getSpringConfig();
|
|
springConfig.tension = 230;
|
|
springConfig.friction = 10;
|
|
|
|
this._scrollSpring.addListener({
|
|
onSpringUpdate: () => {
|
|
this.setState({scale: this._scrollSpring.getCurrentValue()});
|
|
},
|
|
});
|
|
|
|
// Initialize the spring value at 1
|
|
this._scrollSpring.setCurrentValue(1);
|
|
},
|
|
|
|
_onPressIn() {
|
|
this._scrollSpring.setEndValue(0.5);
|
|
},
|
|
|
|
_onPressOut() {
|
|
this._scrollSpring.setEndValue(1);
|
|
},
|
|
|
|
render: function() {
|
|
var imageStyle = {
|
|
width: 250,
|
|
height: 200,
|
|
transform: [{scaleX: this.state.scale}, {scaleY: this.state.scale}],
|
|
};
|
|
|
|
var imageUri = "https://facebook.github.io/react-native/img/ReboundExample.png";
|
|
|
|
return (
|
|
<View style={styles.container}>
|
|
<TouchableWithoutFeedback onPressIn={this._onPressIn}
|
|
onPressOut={this._onPressOut}>
|
|
<Image source={{uri: imageUri}} style={imageStyle} />
|
|
</TouchableWithoutFeedback>
|
|
</View>
|
|
);
|
|
}
|
|
});
|
|
```
|
|
[Run this example](https://rnplay.org/apps/NNI5eA)
|
|
|
|
You can also clamp the spring values so that they don't overshoot and
|
|
oscillate around the end value. In the above example, we would add
|
|
`this._scrollSpring.setOvershootClampingEnabled(true)` to change this.
|
|
See the below gif for an example of where in your interface you might
|
|
use this.
|
|
|
|
 Screenshot from
|
|
[react-native-scrollable-tab-view](https://github.com/brentvatne/react-native-scrollable-tab-view).
|
|
You can run a simlar example [here](https://rnplay.org/apps/qHU_5w).
|
|
|
|
#### A sidenote about setNativeProps
|
|
|
|
As mentioned [in the Direction Manipulation section](/react-native/docs/direct-manipulation.html),
|
|
`setNativeProps` allows us to modify properties of native-backed
|
|
components (components that are actually backed by native views, unlike
|
|
composite components) directly, without having to `setState` and
|
|
re-render the component hierarchy.
|
|
|
|
We could use this in the Rebound example to update the scale - this
|
|
might be helpful if the component that we are updating is deeply nested
|
|
and hasn't been optimized with `shouldComponentUpdate`.
|
|
|
|
```javascript
|
|
// Outside of our React component
|
|
var precomputeStyle = require('precomputeStyle');
|
|
|
|
// Back inside of the App component, replace the scrollSpring listener
|
|
// in componentWillMount with this:
|
|
this._scrollSpring.addListener({
|
|
onSpringUpdate: () => {
|
|
if (!this._photo) { return }
|
|
var v = this._scrollSpring.getCurrentValue();
|
|
var newProps = precomputeStyle({transform: [{scaleX: v}, {scaleY: v}]});
|
|
this._photo.setNativeProps(newProps);
|
|
},
|
|
});
|
|
|
|
// Lastly, we update the render function to no longer pass in the
|
|
// transform via style (avoid clashes when re-rendering) and to set the
|
|
// photo ref
|
|
render: function() {
|
|
return (
|
|
<View style={styles.container}>
|
|
<TouchableWithoutFeedback onPressIn={this._onPressIn} onPressOut={this._onPressOut}>
|
|
<Image ref={component => this._photo = component}
|
|
source={{uri: "https://facebook.github.io/react-native/img/ReboundExample.png"}}
|
|
style={{width: 250, height: 200}} />
|
|
</TouchableWithoutFeedback>
|
|
</View>
|
|
);
|
|
}
|
|
```
|
|
[Run this example](https://rnplay.org/apps/fUqjAg)
|
|
|
|
It would not make sense to use `setNativeProps` with react-tween-state
|
|
because the updated tween values are set on the state automatically by
|
|
the library - Rebound on the other hand gives us an updated value for
|
|
each frame with the `onSpringUpdate` function.
|
|
|
|
If you find your animations with dropping frames (performing below 60
|
|
frames per second), look into using `setNativeProps` or
|
|
`shouldComponentUpdate` to optimize them. You may also want to defer any
|
|
computationally intensive work until after animations are complete,
|
|
using the
|
|
[InteractionManager](/react-native/docs/interactionmanager.html). You
|
|
can monitor the frame rate by using the In-App Developer Menu "FPS
|
|
Monitor" tool.
|
|
|
|
### Navigator Scene Transitions
|
|
|
|
As mentioned in the [Navigator
|
|
Comparison](https://facebook.github.io/react-native/docs/navigator-comparison.html#content),
|
|
`Navigator` is implemented in JavaScript and `NavigatorIOS` is a wrapper
|
|
around native functionality provided by `UINavigationController`, so
|
|
these scene transitions apply only to `Navigator`. In order to re-create
|
|
the various animations provided by `UINavigationController` and also
|
|
make them customizable, React Native exposes a
|
|
[NavigatorSceneConfigs](https://github.com/facebook/react-native/blob/master/Libraries/CustomComponents/Navigator/NavigatorSceneConfigs.js) API.
|
|
|
|
```javascript
|
|
var SCREEN_WIDTH = require('Dimensions').get('window').width;
|
|
var BaseConfig = Navigator.SceneConfigs.FloatFromRight;
|
|
|
|
var CustomLeftToRightGesture = Object.assign({}, BaseConfig.gestures.pop, {
|
|
// Make it snap back really quickly after canceling pop
|
|
snapVelocity: 8,
|
|
|
|
// Make it so we can drag anywhere on the screen
|
|
edgeHitWidth: SCREEN_WIDTH,
|
|
});
|
|
|
|
var CustomSceneConfig = Object.assign({}, BaseConfig, {
|
|
// A very tighly wound spring will make this transition fast
|
|
springTension: 100,
|
|
springFriction: 1,
|
|
|
|
// Use our custom gesture defined above
|
|
gestures: {
|
|
pop: CustomLeftToRightGesture,
|
|
}
|
|
});
|
|
```
|
|
[Run this example](https://rnplay.org/apps/HPy6UA)
|
|
|
|
For further information about customizing scene transitions, [read the
|
|
source](https://github.com/facebook/react-native/blob/master/Libraries/CustomComponents/Navigator/NavigatorSceneConfigs.js).
|
|
|
|
### AnimationExperimental *(Deprecated)*
|
|
|
|
As the name would suggest, this was only ever an experimental API and it
|
|
is **not recommended to use this on your apps**. It has some rough edges
|
|
and is not under active development. It is built on top of CoreAnimation
|
|
explicit animations.
|
|
|
|
If you choose to use it anyways, here is what you need to know:
|
|
|
|
- You will need to include `RCTAnimationExperimental.xcodeproj` and add
|
|
`libRCTAnimationExperimental.a` to `Build Phases`.
|
|
- Suited only for static "fire and forget" animations - not continuous gestures.
|
|
- Hit detection will not work as expected because animations occur on
|
|
the presentation layer.
|
|
|
|
```javascript
|
|
var AnimationExperimental = require('AnimationExperimental');
|
|
|
|
var App = React.createClass({
|
|
componentDidMount() {
|
|
AnimationExperimental.startAnimation(
|
|
{
|
|
node: this._box,
|
|
duration: 1000,
|
|
easing: 'easeInOutBack',
|
|
property: 'scaleXY',
|
|
toValue: { x: 1, y: 1 },
|
|
},
|
|
);
|
|
},
|
|
|
|
render() {
|
|
return (
|
|
<View style={{flex: 1, justifyContent: 'center', alignItems: 'center'}}>
|
|
<View ref={component => this._box = component}
|
|
style={{width: 200, height: 200, backgroundColor: 'red'}} />
|
|
</View>
|
|
)
|
|
},
|
|
});
|
|
```
|
|
|
|
|
|
Now to demonstrate a known issue, and one of the reasons why it is
|
|
recommended not to use `AnimationExperimental` currently, let's try to
|
|
animate `opacity` from 1 to 0.5:
|
|
|
|
```javascript
|
|
AnimationExperimental.startAnimation(
|
|
{
|
|
node: this._box,
|
|
duration: 1000,
|
|
easing: 'easeInOutBack',
|
|
property: 'opacity',
|
|
fromValue: 1,
|
|
toValue: 0.5,
|
|
},
|
|
);
|
|
```
|
|
|
|
|
|
|
|
### Pop *(Unsupported, not recommended)*
|
|
|
|
[Facebook Pop](https://github.com/facebook/pop) "supports spring and
|
|
decay dynamic animations, making it useful for building realistic,
|
|
physics-based interactions."
|
|
|
|
This is not officially supported or recommended because the direction is
|
|
to move towards JavaScript-driven animations, but if you must use it,
|
|
you can find the code to integrate with React Native
|
|
[here](https://github.com/facebook/react-native/issues/1365#issuecomment-104792251).
|
|
Please do not open questions specific to Pop on the React Native issues,
|
|
StackOverflow is a better place to answer those questions as it is not
|
|
considered to be part of the core.
|