I'm using react-navigation's DrawerNavigator in my app. I would like to detect when a user drags open the side menu so that i can perform a certain action, e.g dismiss an opened Keyboard.
How can i do this? i can't seem to find a solution in the docs. Thank you.

Here is my code
---------------

```js
import React from 'react';
import { Dimensions } from 'react-native';
import { Icon } from 'react-native-elements';
import { DrawerNavigator, StackNavigator, addNavigationHelpers } from 'react-navigation';

//redux related imports
import { createStore, combineReducers } from 'redux';
import { Provider, connect } from 'react-redux';

import Attendance from './containers/pages/Attendance';
import Fees from './containers/pages/Fees';
import Exams from './containers/pages/Exams';
import InitializeUser from './containers/pages/InitializeUser';
import Landing from './Landing';
import Login from './containers/pages/Login';
import Search from './containers/pages/Search';
import Staff from './containers/pages/Staff';
import Stats from './containers/pages/Stats';
import Students from './containers/pages/Students';
import Verification from './containers/pages/verify';
import ProfileDetail from './components/pages/ProfileDetail';
import FeesDetail from './containers/pages/FeesDetails';

import MainReport from './containers/pages/Reports/Main_Report';
import AcademicDetails from './containers/pages/Reports/Student_Academic_Details';
import { Constants } from './config';
import ResultsLanding from './containers/pages/Reports/ResultsLanding';
import { CustomDrawerContentComponent } from '../src/components/base/SideMenu';

const screenWidth = Dimensions.get('window').width;
const MainPages = DrawerNavigator({
  StudentsPage: {
    path: '/Students',
    screen: Students
  },
  SearchPage: {
    path: '/Seacrh',
    screen: Search
  },

  Staff: {
    path: '/Staff',
    screen: Staff
  },

  Fees: {
    path: '/Fees',
    screen: Fees
  },
  Stats: {
    path: '/Stats',
    screen: Stats
  },
  Results: {
    screen: ResultsLanding,
    navigationOptions: {
      tintColor: 'red',
      flex: 1,
      drawerIcon: ({ tintColor }) => (
        <Icon
          name="content-paste"
          color={tintColor}
        />
      )
    }
  },
  Attendance:
  {
    path: '/Attendance',
    screen: Attendance
  },
},
  {
    initialRouteName: 'StudentsPage',
    contentOptions: {
      activeTintColor: Constants.ui.THEME,
      activeBackgroundColor: 'rgba(0,0,0,0.1)',
      inactiveTintColor: 'rgba(0,0,0,0.6)',
      labelStyle: {
        fontSize: 12,
        marginLeft: 10,
      },
    },

    drawerWidth: screenWidth > 320 ? 300 : 250,
    contentComponent: CustomDrawerContentComponent

  });

export const Navigator = StackNavigator({
  LandingPage: {
    screen: Landing,
    navigationOptions: {
      header: null
    }
  },
  LoginPage: {
    screen: Login,
    navigationOptions: {
      header: null
    },
  },
  ProfileDetailPage: {
    screen: ProfileDetail,
    headerMode: 'screen',
    navigationOptions: {
      header: null
    }
  },
  FeesDetailPage:
  {
    screen: FeesDetail,
    navigationOptions: {
      header: null
    },
  },
  VerifyPage: {
    screen: Verification,
    navigationOptions: {
      header: null
    },
  },
  InitUserPage: {
    screen: InitializeUser,
    navigationOptions: {
      header: null
    },
  },
  MainPages: {
    screen: MainPages,
    navigationOptions: {
      header: null
    }
  },

  MainReportPage: {
    screen: MainReport,
    navigationOptions: {
      header: null
    }
  },
  ExamsMainPage: {
    screen: Exams,
    navigationOptions: {
      header: null
    }
  },
  AcademicDetailsPage: {
    screen: AcademicDetails,
    navigationOptions: {
      header: null
    }
  },

});  

const initialState = MainPages.router.getStateForAction(
  MainPages.router.getActionForPathAndParams('StudentsPage'));  

const navReducer = (state = initialState, action) => {
  const nextState = MainPages.router.getStateForAction(action, state);
  return nextState || state;
}; 

const appReducer = combineReducers({
  nav: navReducer
});

class App extends React.Component {
  componentWillReceiveProps(nextProps) {
    console.warn('nextProps: ', JSON.stringify(nextProps, null, 4));
  }
  render() {
    return (
      <MainPages 
        navigation={addNavigationHelpers({
        dispatch: this.props.dispatch,
        state: this.props.nav,
      })} />
    );
  }
}

const mapStateToProps = (state) => ({
  nav: state.nav
});

const AppWithNavigationState = connect(mapStateToProps)(App);

const store = createStore(appReducer);

class Root extends React.Component {
  render() {
    return (
      <Provider store={store}>
        <AppWithNavigationState />
      </Provider>
    );
  }
}
```

[enter image description here](https://i.stack.imgur.com/PTUA2.png)
Here is a screenshot of the error i get when i run the code