如何使用react-native-map中的自定义按钮转到我当前的位置？

npm install react-native-maps --save

import MapView, { Marker, Callout } from 'react-native-maps';
import { Button } from 'react-native';

render() {
  return (
    <View style={styles.container}>
      <MapView
        style={styles.map}
        initialRegion={{
          latitude: 37.78825,
          longitude: -122.4324,
          latitudeDelta: 0.0922,
          longitudeDelta: 0.0421,
        }}
      >
        <Marker
          coordinate={{
            latitude: 37.78825,
            longitude: -122.4324,
          }}
        >
          <Callout>
            <Text>This is a marker</Text>
          </Callout>
        </Marker>
      </MapView>
      <Button
        title="Go to My Location"
        onPress={this.goToMyLocation}
      />
    </View>
  );
}

goToMyLocation = () => {
  navigator.geolocation.getCurrentPosition(
    position => {
      const { latitude, longitude } = position.coords;
      this.map.animateToRegion({
        latitude,
        longitude,
        latitudeDelta: 0.0922,
        longitudeDelta: 0.0421,
      });
    },
    error => alert(error.message),
    { enableHighAccuracy: true, timeout: 20000, maximumAge: 1000 }
  );
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
  },
  map: {
    ...StyleSheet.absoluteFillObject,
  },
});