index.js

import React, { Component } from "react";
import { View, StyleSheet, Animated } from "react-native";

class AnimatedBar extends Component {
  state = {
    animation: new Animated.Value(this.props.progress),
  };

  componentWillMount() {
    this.widthInterpolate = this.state.animation.interpolate({
      inputRange: [0, 1],
      outputRange: ["0%", "100%"],
      extrapolate: "clamp",
    });
  }

  componentDidMount() {
    this.attachListener();
  }

  attachListener = () => {
    this.removeListeners();

    if (typeof this.props.onAnimate === "function") {
      this.attachListener(this.props.onAnimate);
    }
  };
  removeListeners = () => {
    this.state.animation.removeAllListeners();
  };
  componentWillUnmount() {
    this.removeListeners();
  }

  componentDidUpdate(prevProps, prevState) {
    //If our function changes then attach the new one
    if (prevProps.onAnimate !== this.props.onAnimate) {
      this.attachListener();
    }

    //If our progress has changed we should animate
    if (prevProps.progress !== this.props.progress) {
      if (this.props.animate) {
        Animated.timing(this.state.animation, {
          useNativeDriver: false, // Hardware rendering doesn't sit well with module
          toValue: this.props.progress,
          duration: this.props.duration,
        }).start();
      } else {
        this.state.animation.setValue(this.props.progress);
      }
    }
  }

  render() {
    const {
      children,
      height,
      borderColor,
      borderWidth,
      borderRadius,
      barColor,
      fillColor,
      row,
      style,
      wrapStyle,
      fillStyle,
      barStyle,
    } = this.props;

    return (
      <Animated.View style={[styles.outer, { height }, row ? styles.flex : undefined, style]}>
        <Animated.View style={[styles.flex, { borderColor, borderWidth, borderRadius }, wrapStyle]}>
          <Animated.View
            style={[StyleSheet.absoluteFill, { backgroundColor: fillColor }, fillStyle]}
          />
          <Animated.View
            style={[
              styles.bar,
              {
                width: this.widthInterpolate,
                backgroundColor: barColor,
              },
              barStyle,
            ]}
          />
          {children}
        </Animated.View>
      </Animated.View>
    );
  }
}

const styles = StyleSheet.create({
  outer: {
    flexDirection: "row",
  },
  flex: {
    flex: 1,
  },
  bar: {
    position: "absolute",
    left: 0,
    top: 0,
    bottom: 0,
  },
});

AnimatedBar.defaultProps = {
  height: 10,
  borderColor: "#000",
  borderWidth: 1,
  borderRadius: 0,
  barColor: "#FFF",
  fillColor: "rgba(0,0,0,.5)",
  duration: 100,
  animate: true,
};

export default AnimatedBar;