如何使用Material UI withStyle为css类应用样式。WithStyle不工作

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

const styles = {
  myClass: {
    backgroundColor: 'blue',
    color: 'white',
    padding: '10px',
  },
};

const MyComponent = (props) => {
  const { classes } = props;
  return (
    <div className={classes.myClass}>
      This is my component.
    </div>
  );
};

const StyledComponent = withStyles(styles)(MyComponent);

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

const styles = {
  myClass: {
    backgroundColor: 'blue',
    color: 'white',
    padding: '10px',
  },
};

const MyComponent = (props) => {
  const { classes } = props;
  return (
    <div className={classes.myClass}>
      This is my component.
    </div>
  );
};

const StyledComponent = withStyles(styles)(MyComponent);

export default StyledComponent;