text: import { createAppContainer } from 'react-navigation';
  import { createStackNavigator } from 'react-navigation-stack';
  
  import Main from './pages/Main';
  import User from './pages/User';
  import Repository from './pages/Repository';
  
  const Routes = createAppContainer(
    createStackNavigator({
      Main, User, Repository
    }, {
      headerLayoutPreset: 'center',
      defaultNavigationOptions: {
        headerBackTitleVisible: false,
        headerStyle: {
          backgroundColor: '#7159c1',
        },
        headerTintColor: '#EEE'
      }
    })
  );
  
  export default Routes;
  