title: React Native -- Nativebase drawer not open in my project
body: <p>i am working on react native nativebase drawer component in my application so i follow all steps as below</p>
  
  <p>package.json</p>
  
  <pre><code>"dependencies": {
  "@expo/vector-icons": "^6.2.2",
  "native-base": "^2.3.7",
  "react": "16.0.0",
  "react-native": "0.51.0",
  "react-native-device-info": "^0.13.0",
  "react-native-router-flux": "^4.0.0-beta.28",
  "react-navigation": "^1.0.0-beta.27"
  },
  </code></pre>
  
  <p>Menuscreen.js</p>
  
  <pre><code>render(){
  
  return(
  
    &lt;Drawer
        ref={(comp) =&gt; {this.drawer = comp}}
        content={this.drawerContent()}
        type={'overlay'}
        panThreshold={0.30}
        panOpenMask={this.state.panOpenMask}
        onClose={() =&gt; this.closeDrawer()}
        &gt;
        {this.setView(this.state.viewID)}
  
    &lt;/Drawer&gt;
  )
  }
  </code></pre>
  
  <p>setView Method</p>
  
  <pre><code>setView(id) {
  console.log("setView id;"+ id);
  BackHandler.removeEventListener('hardwareBackPress', this._handleBackPressInDrawer);
  switch (id){
  
    case 0:
      return(
        &lt;HomeScreen drawer={this.drawer}/&gt;
      )
  
    case 1:
      return(
        &lt;ScreenOne drawer={this.drawer}/&gt;
      )
    case 2:
      return(
        &lt;ScreenTwo drawer={this.drawer}/&gt;
      )
      case 3:
      return(
        &lt;ScreenThree drawer={this.drawer}/&gt;
      )
      case 4:
      return(
        &lt;ScreenContacts drawer={this.drawer}/&gt;
      )
    case 5:
      return(
        &lt;ScreenNotes /&gt;
      )
      case 6:
      return(
        &lt;FourScreen drawer={this.drawer}/&gt;
      )
       break;
    default:
  
  }
  }
  </code></pre>
  
  <p>Homescreen.js</p>
  
  <pre><code>render() {
  
  return (
    &lt;Container&gt;
      &lt;Header style={{ alignItems:'center',paddingTop: 0, paddingBottom: 0 }}&gt;
        &lt;Left&gt;
          &lt;Button transparent onPress={()=&gt;{this.props.drawer._root.open()}}&gt;
            &lt;Icon name='menu' /&gt;
          &lt;/Button&gt;
        &lt;/Left&gt;
        &lt;Body style={{alignItems:'flex-start'}} &gt;
          &lt;Title&gt;HOME&lt;/Title&gt;
        &lt;/Body&gt;
      &lt;/Header&gt;
  
    &lt;/Container&gt;
  
  )
  }
  </code></pre>
  
  <p>When I run above code and click on menu icon on the home screen I get an error message in homescreen.js like  </p>
  
  <p><strong>Undefined is not an object (evaluating _this2.propsdrawer.root)</strong> </p>
  
  <p>Any idea how can I solve this? your all suggestions are appreciable  </p>