react native useRef not working: TypeError: undefined is not an object (evaluating

Question

i want to call methd _getRoomList() from child(named RecentScreen) when parent(namedHomeScreen) already. Here is my code:

home

export default function HomeScreen() {
const headerChildRef = React.useRef()

const _getMasterInfoApi = () => {
        ApiHelper.getData(ApiConstant.GET_MASTER_INFO, 
            '_getMasterInfoApi')
            .then(data => {
                ....
                headerChildRef.current._getRoomList() => i want to get roomlist from here
            })
    };

 useEffect(() => {
        console.log('home')
        _getMasterInfoApi()
    }, [])

here is HomeScreen view and config ref

here is RecentScreen:

export default function RecentlyScreen({ref}) {
  const {masterInfo} = React.useContext(MasterInfoContext)
  let currentUser = masterInfo?.CurrentUser

  const [roomList, setRoomList] = React.useState([])

  _getRoomList = () => {
    const getRoomUrl = currentUser?.Server.Address + ApiConstant.GET_ROOM_LIST
    console.log('getRoomUrl', getRoomUrl)
    ApiHelper.postData(getRoomUrl, 
      {
        'Skip' : 0,
        'Take' : 20
      },
      '_getRoomList')
      .then(data => {
        const rooms = data.Data
        setRoomList(rooms)
      })
  }

But i got this error:

TypeError: undefined is not an object (evaluating 'headerChildRef.current._getRoomList')

can anyone guide me to know the problem? Thanks