React Native: Triggering Animation on hide

Question

I have an element controlling the rendering of a child element. (A TouchableHighlight that sets some state in its onPress.) In the child element's componentDidMount method I construct an Animated.spring and start it. This works for entry, but I need to do the same animation in reverse to exit (it's like a drawer). componentWillUnmount executes too quickly for Animated.spring to even start working.

How would I handle animating the child's exit?

Answer 1

I have implemented a FadeInOut component that will animate a component in or out when its isVisible property changes. I made it because I wanted to avoid explicitly handling the visibility state in the components that should enter/exit with an animation.

<FadeInOut isVisible={this.state.someBooleanProperty} style={styles.someStyle}>
  <Text>Something...</Text>
</FadeInOut>

This implementation uses a delayed fade, because I use it for showing progress indicator, but you can change it to use any animation you want, or generalise it to accept the animation parameters as props:

'use strict';

import React from 'react-native';

const {
  View,
  Animated,
  PropTypes
} = React;

export default React.createClass({
  displayName: 'FadeInOut',
  propTypes: {
    isVisible: PropTypes.bool.isRequired,
    children: PropTypes.node.isRequired,
    style: View.propTypes.style
  },

  getInitialState() {
    return {
      view: this.props.children,
      opacity: new Animated.Value(this.props.isVisible ? 1 : 0)
    };
  },

  componentWillReceiveProps(nextProps) {
    const isVisible = this.props.isVisible;
    const shouldBeVisible = nextProps.isVisible;

    if (isVisible && !shouldBeVisible) {
      Animated.timing(this.state.opacity, {
        toValue: 0,
        delay: 500,
        duration: 200
      }).start(this.removeView);
    }

    if (!isVisible && shouldBeVisible) {
      this.insertView();
      Animated.timing(this.state.opacity, {
        toValue: 1,
        delay: 500,
        duration: 200
      }).start();
    }
  },

  insertView() {
    this.setState({
      view: this.props.children
    });
  },

  removeView() {
    this.setState({
      view: null
    });
  },

  render() {
    return (
      <Animated.View
        pointerEvents={this.props.isVisible ? 'auto' : 'none'}
        style={[this.props.style, {opacity: this.state.opacity}]}>
        {this.state.view}
      </Animated.View>
    );
  }
});