如何在formik中设置值？

import { useFormik } from 'formik';

const MyForm = () => {
  const formik = useFormik({
    initialValues: {
      username: '',
    },
    onSubmit: values => {
      console.log(values);
    },
  });

  const handleSetValue = () => {
    formik.setFieldValue('username', 'example');
  };

  return (
    <form onSubmit={formik.handleSubmit}>
      <input
        type="text"
        name="username"
        value={formik.values.username}
        onChange={formik.handleChange}
      />
      <button type="submit">Submit</button>
      <button type="button" onClick={handleSetValue}>Set Value</button>
    </form>
  );
};