text: import React from 'react';
  import Backdrop from '@material-ui/core/Backdrop';
  import CircularProgress from '@material-ui/core/CircularProgress';
  import { makeStyles } from '@material-ui/core/styles';
  
  const useStyles = makeStyles((theme) => ({
    backdrop: {
      zIndex: theme.zIndex.drawer + 1,
      color: '#fff',
    },
  }));
  
  export default function SimpleBackdrop() {
    const classes = useStyles();
    const [open, setOpen] = React.useState(true);
    const handleClose = () => {
      setOpen(false);
    };
  
    return (
      <div>
        <Backdrop className={classes.backdrop} open={open} onClick={handleClose}>
          <CircularProgress color="inherit" />
        </Backdrop>
      </div>
    );
  }