I am using the react-google-maps library. How can I get the coordinates of the center of the map?

Question

Google Maps

I am using the react-google-maps library. There is little information on foreign resources. I read that the coordinates can be obtained through getCenter(), but I can't. How to implement a button in the component that will send the center coordinates to the parent function and how to get these center coordinates? Maybe who knows? Thank you!
Here is the component code

const Map = compose(
    withProps({
        googleMapURL: "https://maps.googleapis.com/maps/api/js?key=AIzaSyB8ECfIjkNyE2AVBlG4Fpd4rD2Y4q5Ytpk",
        loadingElement: <div style={{ height: `100%` }} />,
        containerElement: <div style={{ height: `400px`, }} />,
        mapElement: <div style={{ height: `100%` }} />,
    }),
    lifecycle({
        componentDidMount() {
            const refs = {}

            this.setState({
                onMapMounted: ref => {
                    refs.map = ref;
                    console.log(refs.map.getCenter())
                },
            })
        },
    }),
    withScriptjs,
    withGoogleMap
)((props) =>
    <GoogleMap markers={markers}
        ref={props.onMapMounted}
        defaultZoom={8}
        defaultCenter={{ lat: -34.397, lng: 150.644 }}
    >
        {markers.map( function (obj, index) {
            return (
                <div key={index}>
                    <Marker title="Hello World!" position={{ lat: obj.position.lat, lng: obj.position.lng }} onClick={props.onToggleOpen}>
                        {props.isOpen &&
                            <InfoWindow onCloseClick={props.onToggleOpen}>
                                 <div>
                                     {obj.title}
                                </div>
                            </InfoWindow>
                        }
                    </Marker>
                </div>
            );
        })
        }
        <Polygon path={path} />
    </GoogleMap>
)