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React Native : Implement an animation with Hooks (useEffect, useState)

rayanbassetti profile image Rayan Bassetti ・1 min read

Hi everyone !

First article, ever, I suck at Markdown, let's get to the point.

I've been following an online course (https://openclassrooms.com/fr/courses/4902061-developpez-une-application-mobile-react-native/), which uses Class Components.

2020, we're woke (kinda), I'm doing it with Function Components.

Now some parts have been written taking Classes and React Navigation V4 as a base (which will also require another article in the future), so here's a code to make animations work with Function Components.

Here's the code with a Class :

// Animations/EnlargeShrink.js

import React from 'react'
import { Animated } from 'react-native'

class EnlargeShrink extends React.Component {

  constructor(props) {
    super(props)
    this.state = {
      viewSize: new Animated.Value(this._getSize())
    }
  }

  _getSize() {
    if (this.props.shouldEnlarge) {
      return 80
    }
    return 40
  }
  // La méthode componentDidUpdate est exécuté chaque fois que le component est mise à jour, c'est l'endroit parfait pour lancer / relancer notre animation.
  componentDidUpdate() {
    Animated.spring(
      this.state.viewSize,
      {
        toValue: this._getSize()
      }
    ).start()
  }

  render() {
    return (
        <Animated.View
          style={{ width: this.state.viewSize, height: this.state.viewSize }}>
          {this.props.children}
        </Animated.View>
    )
  }
}

export default EnlargeShrink
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And here's the code with a function :

import React, { useEffect, useState } from 'react'
import { Animated } from 'react-native'

export default function FavTouch({children, shouldEnlarge}) {
    const [size, setSize] = useState(new Animated.Value(shouldEnlarge ? 80:40))

    useEffect(() => {
        Animated.spring(
            size,
            {
                toValue: shouldEnlarge ? 80 : 40,
                useNativeDriver: false
            },
        ).start()
    }, [shouldEnlarge])

    return (
        <Animated.View style={{width: size, height: size}}>
            {children}
        </Animated.View>
    )
}
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Feel free to give heads-up/changes if needed, see you around !

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