以下代碼是要附加多個事件偵聽器還是 React Native / expo-linking 一次只允許附加一個事件偵聽器？import * as Linking from 'expo-linking'import { useIsFocused } from '@react-navigation/native'const MyComponent = () => {  const isFocused = useIsFocused()  useEffect(() => {    fetchData()    Linking.addEventListener('url', _handleEvent)  }, [isFocused])  const fetchData = () => {    // ...  }  const _handleEvent = () => {    // ...  }  return (    <View><View>  )}有沒有辦法檢查事件監聽器是否已經存在，所以我可以做類似的事情：useEffect(() => {  fetchData()  if(!eventListenerExists){    Linking.addEventListener('url', _handleEvent)  }}, [isFocused])