PlatformAndWebview.js

import { PureComponent } from 'react'
import { Platform, WebView as WebViewAndroid } from 'react-native'
import WebViewIOS from 'react-native-wkwebview-reborn'

const webviewRef = 'webview'

...

class App extends PureComponent {
   ...

  webviewProps = {
    ref: webviewRef,
    onNavigationStateChange: this.handleNavigationStateChange.bind(this),
    onMessage: this.handleMessage.bind(this),
    javaScriptEnabled: true,
    source: {
      uri: 'https://yourloginurl.com',
    }
  }

  render() {
    return (
      Platform.OS === 'ios' ?
      <WebViewIOS {...this.webviewProps} /> :
      <WebViewAndroid {...this.webviewProps} />
    )
  }
}