like inbox right bottom button, always fix

FixButton.js

import React, { PropTypes } from 'react'
import FloatingActionButton from 'material-ui/lib/floating-action-button';

const FixButton = ({ onAddClick }) => {
  return (
    <FloatingActionButton
      style={{ right: 20, bottom: 20, position: 'fixed' }}
      onClick={onAddClick}>
      <ContentAdd />
    </FloatingActionButton>
  )
}

FixButton.propTypes = {
  onAddClick: PropTypes.func.isRequired,
}

export default FixButton;