ScollableHeader-5.js

...

constructor(props) {
  super(props);

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

...
  
render() {
  const headerHeight = this.state.scrollY.interpolate({
    inputRange: [0, HEADER_SCROLL_DISTANCE],
    outputRange: [HEADER_MAX_HEIGHT, HEADER_MIN_HEIGHT],
    extrapolate: 'clamp',
  });
  
  ...

  <ScrollView
    style={styles.fill}
    scrollEventThrottle={16}
    onScroll={Animated.event(
      [{nativeEvent: {contentOffset: {y: this.state.scrollY}}}]
    )}
  >
    ...
  </ScrollView>
  <Animated.View style={[styles.header, {height: headerHeight}]}>
    ...
  </Animated.View>
  ...
}