如何在React with Material-UI中垂直和水平居中？

import React from 'react';
import { makeStyles } from '@material-ui/core/styles';

const useStyles = makeStyles({
  container: {
    display: 'flex',
    alignItems: 'center',
    height: '100vh',
  },
});

function MyComponent() {
  const classes = useStyles();

  return (
    <div className={classes.container}>
      {/* 子元素 */}
    </div>
  );
}

export default MyComponent;

import React from 'react';
import { makeStyles } from '@material-ui/core/styles';

const useStyles = makeStyles({
  container: {
    display: 'flex',
    justifyContent: 'center',
    height: '100vh',
  },
});

function MyComponent() {
  const classes = useStyles();

  return (
    <div className={classes.container}>
      {/* 子元素 */}
    </div>
  );
}

export default MyComponent;

import React from 'react';
import { makeStyles } from '@material-ui/core/styles';

const useStyles = makeStyles({
  container: {
    display: 'flex',
    alignItems: 'center',
    justifyContent: 'center',
    height: '100vh',
  },
});

function MyComponent() {
  const classes = useStyles();

  return (
    <div className={classes.container}>
      {/* 子元素 */}
    </div>
  );
}

export default MyComponent;