我试图从Material-UI framework中获取AppBar（http://www.Material-UI.com/#/components/app-bar）左侧的导航，默认汉堡图标，以便在单击时滑动打开抽屉组件（http://www.Material-UI.com/#/components/Drawer）。但一旦点击，我会得到以下错误，我看不出来:

未捕获的TypeError:无法读取未定义的属性“open”

如能就此提供任何见解或指导，将不胜感激。提前谢谢你。

import React, { Component } from 'react'
import { Drawer, AppBar, MenuItem} from 'material-ui'
import baseTheme from 'material-ui/styles/baseThemes/lightBaseTheme'
import getMuiTheme from 'material-ui/styles/getMuiTheme'
import { Route, Router } from 'react-router'



export default class Main extends Component  {

  constructor(props, context){
    super(props, context);
    this.state = {open:false};
  }

  getChildContext() {
    return {muiTheme: getMuiTheme(baseTheme)};
  }

  handleToggle() {
    this.setState({open: !this.state.open});
   }

        render() {
            return (
                <div>
                <AppBar   
                  isInitiallyOpen={true} 
                  onLeftIconButtonTouchTap={this.handleToggle}        
                  onLeftIconButtonClick={this.handleToggle} 
                />

                <Drawer
                  docked={false}
                  open={this.state.open}>
                  <MenuItem>Menu Item 1</MenuItem>
                  <MenuItem>Menu Item 2</MenuItem>
                  <MenuItem>Menu Item 3</MenuItem>
                </Drawer>
                </div>
            );
        }
    }

export default Main;