如何使用react-native-router-flux使导航栏上的按钮居中？

npm install react-native-router-flux --save

import { Actions } from 'react-native-router-flux';
import { Header, Button, Icon, Title } from 'native-base';

render() {
  return (
    <Header style={{ justifyContent: 'center', alignItems: 'center' }}>
      <Button transparent onPress={Actions.pop}>
        <Icon name="arrow-back" />
      </Button>
      <Title>页面标题</Title>
      <Button transparent>
        <Icon name="menu" />
      </Button>
    </Header>
  );
}