在React Native Maps多边形中更改fillColor的不透明度？

import React from 'react';
import { View } from 'react-native';
import MapView, { Polygon } from 'react-native-maps';

const MyMap = () => {
  const polygonCoordinates = [
    { latitude: 37.8025259, longitude: -122.4351431 },
    { latitude: 37.7896386, longitude: -122.421646 },
    { latitude: 37.7665248, longitude: -122.4161628 },
    { latitude: 37.7734153, longitude: -122.4577787 }
  ];

  const polygonFillColor = 'rgba(255, 0, 0, 0.5)'; // 设置不透明度为0.5

  return (
    <View style={{ flex: 1 }}>
      <MapView style={{ flex: 1 }}>
        <Polygon
          coordinates={polygonCoordinates}
          fillColor={polygonFillColor}
        />
      </MapView>
    </View>
  );
};

export default MyMap;