useEffect(() => {
    return navigation.addListener('focus', () => {
      console.log("Focused");
      setPosts([])
    });
  }, [navigation]);

  useEffect( () => {
    const requestPermission = async () => {
      const {status} = await BarCodeScanner.requestPermissionsAsync();
      setHasPermission(status === "granted");
    };
    const fetchData = async () => {
      setIsError(false);
      try {
        console.log("Fetching Data");
        const result = await axios(url);
        setPosts(result.data);
      } catch (error) {
        setIsError(true);
      }
    };
    requestPermission().then(r=> console.log(r));
    fetchData().then(r => console.log(r));
  }, [url]);

Scan

Result

fetching data