The Connect Widget

public class MainActivity extends AppCompatActivity {
    private WebView webView = null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
      webView = (WebView) findViewById(R.id.webview);
      webView.setWebViewClient(new AtriumWebViewClient());
      webView.getSettings().setDomStorageEnabled(true);
      webView.getSettings().setJavaScriptEnabled(true);
    }
    private class AtriumWebViewClient extends WebViewClient {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            if (url.equals("atrium://mxConnectLoaded")) {
                //Take action here.
                return true;
            } else if (url.startsWith("atrium://memberAdded")) {
                //Grab member guid and take action here.
                return true;
            }
            return false;
        }
    }
}

class ViewController: UIViewController, WKUIDelegate {
  override func viewDidLoad() {
      super.viewDidLoad()
      webView.delegate = self
      ...
  }

  func webView(_ webView: WKWebView, decidePolicyFor
    navigationAction: WKNavigationAction,
    decisionHandler: @escaping (WKNavigationActionPolicy) -> Swift.Void) {

    // Intercept custom URI
    let surl = navigationAction.url?.absoluteString
    if (surl?.hasPrefix("atrium://"))! {
      // Take action here

      // Cancel request
      decisionHandler(.cancel)
      return
    }

    // Allow request
    decisionHandler(.allow)
  }
}

/**
 * This Client will capture urls from MX and cancel them. It will specifically
 * handle the oauthRequested URL. You will want to set this client as your
 * WebView's client or add this functionality to your own.
 */
public class MXWebViewClient extends WebViewClient {
    private Activity activity;

    public MXWebViewClient(Activity mainActivity) {
        activity = mainActivity;
    }

    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        // Ensure you are looking for schemes from both 'mx', 'atrium' and whatever you configured
        // ui_message_webview_url_scheme to be. In this example, it was 'appscheme'.
        boolean isFromMX = url.startsWith("mx://")  || url.startsWith("atrium://") || url.startsWith("appscheme://");

        if (isFromMX) {
            try {
                Uri mxURI = Uri.parse(url);

                // Handle the oauth url redirect. Send the user to the URL given.
                if (mxURI.getPath().equals("/oauthRequested")) {
                    JSONObject mxMetaData = new JSONObject(mxURI.getQueryParameter("metadata"));
                    String oauthURL = mxMetaData.getString("url");
                    Uri oauthPage = Uri.parse(oauthURL);
                    Intent intent = new Intent(Intent.ACTION_VIEW, oauthPage);
                    activity.startActivity(intent);
                }
            } catch (Exception err) {
                Log.e("sb: Error creating URI", err.getMessage());
            }
            return true;
        }

        return false;
    }
}

/**
 * Set up the WebView to capture URLs. You will want to cancel all urls from MX.
 */
class ViewController: UIViewController, WKNavigationDelegate {

    var webView: WKWebView!
    let appScheme = "appscheme://"
    let mxScheme = "mx://"
    let atriumScheme = "atrium://"

    func webView(_ webView: WKWebView,
                 decidePolicyFor navigationAction: WKNavigationAction,
                 decisionHandler: @escaping (WKNavigationActionPolicy) -> Swift.Void) {

        // Ensure you are looking for schemes from both 'mx', 'atrium', and whatever you configured
        // ui_message_webview_url_scheme to be. In this example, it was 'appscheme'.
        let url = navigationAction.request.url?.absoluteString
        let isFromMX = url?.hasPrefix(appScheme) == true || url?.hasPrefix(mxScheme) == true || url?.hasPrefix(atriumScheme) == true

        if isFromMX {
            let urlc = URLComponents(string: surl ?? "")
            let path = urlc?.path ?? ""
            // there is only one query parameter ("metadata")
            // so just grab the first one
            let metaDataQueryItem = urlc?.queryItems?.first

            if path == "/oauthRequested" {
                handleOauthRedirect(payload: metaDataQueryItem)
            }

            // Cancel request
            decisionHandler(.cancel)
            return
        }

        // Allow request
        decisionHandler(.allow)
    }

    /*
     * Handle the oauthRequested event. Parse out the OAuth URL from the event
     * and open Safari to that URL
     * NOTE: This code is somewhat optimistic, you'll want to add error handling
     * that makes sense for your app.
     */
    func handleOauthRedirect(payload: URLQueryItem?) {
        let metadataString = payload?.value ?? ""

        do {
            if let json = try JSONSerialization.jsonObject(with: Data(metadataString.utf8), options: []) as? [String: Any] {
                if let url = json["url"] as? String {
                    // open safari with the url from the json payload
                    UIApplication.shared.open(URL(string: url)!)
                }
            }
        } catch let error as NSError {
            print("Failed to parse payload: \(error.localizedDescription)")
        }
    }
}