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easing
Easing

import Tabs from '@theme/Tabs'; import TabItem from '@theme/TabItem'; import constants from '@site/core/TabsConstants';

The Easing module implements common easing functions. This module is used by Animated.timing() to convey physically believable motion in animations.

You can find a visualization of some common easing functions at https://easings.net/

Predefined animations

The Easing module provides several predefined animations through the following methods:

  • back provides a basic animation where the object goes slightly back before moving forward
  • bounce provides a bouncing animation
  • ease provides a basic inertial animation
  • elastic provides a basic spring interaction

Standard functions

Three standard easing functions are provided:

The poly function can be used to implement quartic, quintic, and other higher power functions.

Additional functions

Additional mathematical functions are provided by the following methods:

  • bezier provides a cubic bezier curve
  • circle provides a circular function
  • sin provides a sinusoidal function
  • exp provides an exponential function

The following helpers are used to modify other easing functions.

  • in runs an easing function forwards
  • inOut makes any easing function symmetrical
  • out runs an easing function backwards

Example

import React from 'react';
import {
  Animated,
  Easing,
  SectionList,
  StatusBar,
  StyleSheet,
  Text,
  TouchableOpacity,
  View,
} from 'react-native';

const App = () => {
  let opacity = new Animated.Value(0);

  const animate = easing => {
    opacity.setValue(0);
    Animated.timing(opacity, {
      toValue: 1,
      duration: 1200,
      easing,
      useNativeDriver: true,
    }).start();
  };

  const size = opacity.interpolate({
    inputRange: [0, 1],
    outputRange: [0, 80],
  });

  const animatedStyles = [
    styles.box,
    {
      opacity,
      width: size,
      height: size,
    },
  ];

  return (
    <View style={styles.container}>
      <StatusBar hidden={true} />
      <Text style={styles.title}>Press rows below to preview the Easing!</Text>
      <View style={styles.boxContainer}>
        <Animated.View style={animatedStyles} />
      </View>
      <SectionList
        style={styles.list}
        sections={SECTIONS}
        keyExtractor={item => item.title}
        renderItem={({item}) => (
          <TouchableOpacity
            onPress={() => animate(item.easing)}
            style={styles.listRow}>
            <Text>{item.title}</Text>
          </TouchableOpacity>
        )}
        renderSectionHeader={({section: {title}}) => (
          <Text style={styles.listHeader}>{title}</Text>
        )}
      />
    </View>
  );
};

const SECTIONS = [
  {
    title: 'Predefined animations',
    data: [
      {title: 'Bounce', easing: Easing.bounce},
      {title: 'Ease', easing: Easing.ease},
      {title: 'Elastic', easing: Easing.elastic(4)},
    ],
  },
  {
    title: 'Standard functions',
    data: [
      {title: 'Linear', easing: Easing.linear},
      {title: 'Quad', easing: Easing.quad},
      {title: 'Cubic', easing: Easing.cubic},
    ],
  },
  {
    title: 'Additional functions',
    data: [
      {
        title: 'Bezier',
        easing: Easing.bezier(0, 2, 1, -1),
      },
      {title: 'Circle', easing: Easing.circle},
      {title: 'Sin', easing: Easing.sin},
      {title: 'Exp', easing: Easing.exp},
    ],
  },
  {
    title: 'Combinations',
    data: [
      {
        title: 'In + Bounce',
        easing: Easing.in(Easing.bounce),
      },
      {
        title: 'Out + Exp',
        easing: Easing.out(Easing.exp),
      },
      {
        title: 'InOut + Elastic',
        easing: Easing.inOut(Easing.elastic(1)),
      },
    ],
  },
];

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#20232a',
  },
  title: {
    marginTop: 10,
    textAlign: 'center',
    color: '#61dafb',
  },
  boxContainer: {
    height: 160,
    alignItems: 'center',
  },
  box: {
    marginTop: 32,
    borderRadius: 4,
    backgroundColor: '#61dafb',
  },
  list: {
    backgroundColor: '#fff',
  },
  listHeader: {
    paddingHorizontal: 8,
    paddingVertical: 4,
    backgroundColor: '#f4f4f4',
    color: '#999',
    fontSize: 12,
    textTransform: 'uppercase',
  },
  listRow: {
    padding: 8,
  },
});

export default App;

import React from 'react';
import {
  Animated,
  Easing,
  SectionList,
  StatusBar,
  StyleSheet,
  Text,
  TouchableOpacity,
  View,
} from 'react-native';
import type {EasingFunction} from 'react-native';

const App = () => {
  let opacity = new Animated.Value(0);

  const animate = (easing: EasingFunction) => {
    opacity.setValue(0);
    Animated.timing(opacity, {
      toValue: 1,
      duration: 1200,
      easing,
      useNativeDriver: true,
    }).start();
  };

  const size = opacity.interpolate({
    inputRange: [0, 1],
    outputRange: [0, 80],
  });

  const animatedStyles = [
    styles.box,
    {
      opacity,
      width: size,
      height: size,
    },
  ];

  return (
    <View style={styles.container}>
      <StatusBar hidden={true} />
      <Text style={styles.title}>Press rows below to preview the Easing!</Text>
      <View style={styles.boxContainer}>
        <Animated.View style={animatedStyles} />
      </View>
      <SectionList
        style={styles.list}
        sections={SECTIONS}
        keyExtractor={item => item.title}
        renderItem={({item}) => (
          <TouchableOpacity
            onPress={() => animate(item.easing)}
            style={styles.listRow}>
            <Text>{item.title}</Text>
          </TouchableOpacity>
        )}
        renderSectionHeader={({section: {title}}) => (
          <Text style={styles.listHeader}>{title}</Text>
        )}
      />
    </View>
  );
};

const SECTIONS = [
  {
    title: 'Predefined animations',
    data: [
      {title: 'Bounce', easing: Easing.bounce},
      {title: 'Ease', easing: Easing.ease},
      {title: 'Elastic', easing: Easing.elastic(4)},
    ],
  },
  {
    title: 'Standard functions',
    data: [
      {title: 'Linear', easing: Easing.linear},
      {title: 'Quad', easing: Easing.quad},
      {title: 'Cubic', easing: Easing.cubic},
    ],
  },
  {
    title: 'Additional functions',
    data: [
      {
        title: 'Bezier',
        easing: Easing.bezier(0, 2, 1, -1),
      },
      {title: 'Circle', easing: Easing.circle},
      {title: 'Sin', easing: Easing.sin},
      {title: 'Exp', easing: Easing.exp},
    ],
  },
  {
    title: 'Combinations',
    data: [
      {
        title: 'In + Bounce',
        easing: Easing.in(Easing.bounce),
      },
      {
        title: 'Out + Exp',
        easing: Easing.out(Easing.exp),
      },
      {
        title: 'InOut + Elastic',
        easing: Easing.inOut(Easing.elastic(1)),
      },
    ],
  },
];

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#20232a',
  },
  title: {
    marginTop: 10,
    textAlign: 'center',
    color: '#61dafb',
  },
  boxContainer: {
    height: 160,
    alignItems: 'center',
  },
  box: {
    marginTop: 32,
    borderRadius: 4,
    backgroundColor: '#61dafb',
  },
  list: {
    backgroundColor: '#fff',
  },
  listHeader: {
    paddingHorizontal: 8,
    paddingVertical: 4,
    backgroundColor: '#f4f4f4',
    color: '#999',
    fontSize: 12,
    textTransform: 'uppercase',
  },
  listRow: {
    padding: 8,
  },
});

export default App;

Reference

Methods

step0()

static step0(n: number);

A stepping function, returns 1 for any positive value of n.

step1()

static step1(n: number);

A stepping function, returns 1 if n is greater than or equal to 1.

linear()

static linear(t: number);

A linear function, f(t) = t. Position correlates to elapsed time one to one.

https://cubic-bezier.com/#0,0,1,1

ease()

static ease(t: number);

A basic inertial interaction, similar to an object slowly accelerating to speed.

https://cubic-bezier.com/#.42,0,1,1

quad()

static quad(t: number);

A quadratic function, f(t) = t * t. Position equals the square of elapsed time.

https://easings.net/#easeInQuad

cubic()

static cubic(t: number);

A cubic function, f(t) = t * t * t. Position equals the cube of elapsed time.

https://easings.net/#easeInCubic

poly()

static poly(n: number);

A power function. Position is equal to the Nth power of elapsed time.

n = 4: https://easings.net/#easeInQuart n = 5: https://easings.net/#easeInQuint

sin()

static sin(t: number);

A sinusoidal function.

https://easings.net/#easeInSine

circle()

static circle(t: number);

A circular function.

https://easings.net/#easeInCirc

exp()

static exp(t: number);

An exponential function.

https://easings.net/#easeInExpo

elastic()

static elastic(bounciness: number);

A basic elastic interaction, similar to a spring oscillating back and forth.

Default bounciness is 1, which overshoots a little bit once. 0 bounciness doesn't overshoot at all, and bounciness of N > 1 will overshoot about N times.

https://easings.net/#easeInElastic

back()

static back(s)

Use with Animated.parallel() to create a basic effect where the object animates back slightly as the animation starts.

bounce()

static bounce(t: number);

Provides a basic bouncing effect.

https://easings.net/#easeInBounce

bezier()

static bezier(x1: number, y1: number, x2: number, y2: number);

Provides a cubic bezier curve, equivalent to CSS Transitions' transition-timing-function.

A useful tool to visualize cubic bezier curves can be found at https://cubic-bezier.com/

in()

static in(easing: number);

Runs an easing function forwards.

out()

static out(easing: number);

Runs an easing function backwards.

inOut()

static inOut(easing: number);

Makes any easing function symmetrical. The easing function will run forwards for half of the duration, then backwards for the rest of the duration.