text: import React from 'react';
  import { StackNavigator, TabNavigator } from 'react-navigation';
  import { Counter, Welcome } from './screens';
  import { ralph } from './styles';
  
  const stackConfig = {
    navigationOptions: {
      headerStyle: {
        backgroundColor: ralph.primaryColor,
      },
      headerTintColor: ralph.backgroundColor,
    },
  };
  
  const tabConfig = {
    tabBarOptions: {
      activeTintColor: ralph.primaryColor,
    },
  };
  
  const WelcomeNavigator = StackNavigator({
    Welcome: {screen: Welcome},
  }, stackConfig);
  
  const CounterNavigator = StackNavigator({
    Counter: {screen: Counter},
  }, stackConfig);
  
  const AppNavigator = TabNavigator({
    Welcome: {screen: WelcomeNavigator},
    Counter: {screen: CounterNavigator},
  }, tabConfig);
  
  export {
    AppNavigator,
  };
  