React Native: How do you get a Moneris transaction to return to app?

I'm processing a transaction with Moneris in my React Native app in a WebView. The URL in my WebView contains the credentials of my Hosted PayPage Configuration as URI parameters. When creating that configuration on the Moneris site, I need to provide the URL for the hosted paypage to redirect to once the transaction is complete. When I enter something like https://www.google.ca/ as the callback, it works fine, but I don't know what callback URL I'd need to enter to return to my app.

What I Want To Know:

What is the callback URL I'd need to use in order to return to a React Native app?

WebView is just a component inside your app, so you are never leaving your app. First, confirm that page is rendered in a WebView as opposed to launching browser as a separate app and opening a page there (in this case you can't go back to your app programmatically). Then, if you are actually using a WebView component, you could, for example, do the following: add NavigationState listener to your WebView, and read the url the WebView navigates to and take action accordingly

class MyComponent extends React.Component{

  onNavigationStateChange = (navState) => {
    if (navState.url === 'https://www.yoursite.com') {
      // user just got redirected to requested site
      // do something in react-native app now, for example
      // close this component and show another one
    }
  }

  render(){
    return <View>
      <WebView
      ...
      onNavigationStateChange={this.onNavigationStateChange}
    />
    </View>
  }
}