React Native - Fixed header/footer disappearing on scroll

Component.js

import React, { PropTypes, Component } from 'react'
import {
  Animated,
  ScrollView,
  Text,
  View,
} from 'react-native'
import EStyleSheet from 'react-native-extended-stylesheet'

const styles = EStyleSheet.create({
  container: {
    flex: 1,
  },
  scrollView: {
    padding: 20,
  },
  text: {
    marginBottom: 60,
  },
  fixedFooter: {
    backgroundColor: 'blue',
    position: 'absolute',
    bottom: 0,
    left: 0,
    right: 0,
    height: 50,
  }
})


export default class BibleViewer extends Component {
  static propTypes = {

  }

  constructor(props) {
    super(props)

    this.onScrollMoveFooter = ::this.onScrollMoveFooter
  }

  state = {
    scrollY: new Animated.Value(0),
  }

  onScrollMoveFooter(event) {
    const currentOffset = event.nativeEvent.contentOffset.y
    const direction = currentOffset > this.offset ? 'down' : 'up'
    const distance = this.offset ? (this.offset - currentOffset) : 0
    const newPosition = this.state.scrollY._value - distance
    
    if (currentOffset > 0 && currentOffset < (this.contentHeight - this.scrollViewHeight)) { // Don't react at iOS ScrollView Bounce
      if (direction === 'down') {
        if (this.state.scrollY._value < 50) {
          this.state.scrollY.setValue(newPosition > 50 ? 50 : newPosition)
        }
      }
      if (direction === 'up') {
        if (this.state.scrollY._value >= 0) {
          this.state.scrollY.setValue(newPosition < 0 ? 0 : newPosition)
        }
      }
      this.offset = currentOffset
    }
  }

  render() {
    return (
      <View style={styles.container}>
        <ScrollView
          onContentSizeChange={(w, h) => { this.contentHeight = h }}
          onLayout={(ev) => { this.scrollViewHeight = ev.nativeEvent.layout.height }}
          onScroll={this.onScrollMoveFooter}
          scrollEventThrottle={16}
          style={styles.scrollView}
        >
          ...
        </ScrollView>
        <Animated.View
          style={[
            styles.fixedFooter,
            { transform: [{ translateY: this.state.scrollY }] },
          ]}
        />
      </View>
    )
  }
}

Hello,
using this this.onScrollMoveFooter = ::this.onScrollMoveFooter
showing error unexpected token plz help

this.onScrollMoveFooter = this.onScrollMoveFooter.bind(this)

Thanks!