how I can get the response_type code of the redirect_uri of the mercadopago autentication on the webview's expo react native?

Question

I create the app on the Expo React Native and it's necesary that in any time use the auth with mercadopago api to get the response_typo code thast come on redirect url.For this, I use webview, but I cant get the URL that mercadopago returns whit this url. How I can get the redirect and if is that I needed, close the webview to procedure the others functions?

<WebView
      ref={(element) => { this.webViewRef = element; }}
        source={{
          uri: this.state.currentUrl
       }}
        onNavigationStateChange={this.onNavigationStateChange.bind(this)}
        onError={(err)=>console.warn(err)}
        onShouldStartLoadWithRequest = {this.onNavigationStateChange.bind(this)}
        javaScriptEnabled={true}
        domStorageEnabled={true}
        startInLoadingState={true}
        onMessage={this.onMessage}
        style={{ flex: 0, margin: 10,}}
      />

More especific, onNavigationStateChange return the first and second redirect but not work at last redirect where come the code thast I need.

The inicial URL is:

this.setState({ currentUrl: `https://auth.mercadopago.com.ar/authorization?`+
                                `client_id={<ID_of_client>}`+
                                `&response_type=code`+
                                `&platform_id=mp`+
                      `&redirect_uri={<URI_TO_RETURN_THE_CODE_THATS_I_NEED>}` 
                    })