Yandex SmartCaptcha in Android apps

To embed SmartCaptcha in an Android app:

1. Create JavaScript Interface.
2. Configure WebView to work with CAPTCHA.
3. Retrieve the CAPTCHA test results.

Getting startedGetting started

1. Host an HTML page on your server or use the https://smartcaptcha.yandexcloud.net/webview page on the Yandex Cloud server.
2. Create a CAPTCHA.
3. See the Overview tab to get the CAPTCHA keys:
   • Client key: To load the page with CAPTCHA.
   • Server key: To get the CAPTCHA challenge results.

Create a JavaScript InterfaceCreate a JavaScript Interface

1. Create a class to receive messages using a callback function from your web page with CAPTCHA.

2. Define the onGetToken(token: String) method with the @JavascriptInterface annotation. It is called when the web page returns a token for passing CAPTCHA verification:

   class WebJsInterface {
   
     @JavascriptInterface
     fun onGetToken(token: String) {
       //Your code.
     }
   }
   

Configure WebView to work with CAPTCHAConfigure WebView to work with CAPTCHA

1. Create a WebView and add it to the screen.

2. Upload the URL of the web page with CAPTCHA to the WebView.

3. Insert this query parameter into the URL: sitekey=<client_side_key>:

   val webView = findViewById<WebView>(R.id.webViewCaptcha)
   webView.loadUrl("CAPTCHA_page_URL?sitekey=<client_side_key>")
   

4. Add the created JavaScript Interface object to the WebView. Specify NativeClient as the second parameter (this is where the web page will send messages using a callback function):

   settings.javaScriptEnabled = true // Enables JavaScript execution.
   addJavascriptInterface(WebJsInterface(), "NativeClient")
   

Retrieve the CAPTCHA test resultsRetrieve the CAPTCHA test results

1. Save the CAPTCHA verification passed token. It will be returned in the onGetToken(token: String) method after the service processes an attempt.

2. To validate the token, send a POST request to https://smartcaptcha.yandexcloud.net/validate, providing the following parameters in x-www-form-urlencoded format:

   • secret: Server key.
   • token: One-time token received after passing the check.
   • ip: IP address of the user that originated the request to validate the token. This is an optional parameter, but we ask you to provide the user IP when making requests. This helps improve SmartCaptcha performance.

   Note

   This logic must be implemented on the backend. Make sure the secret secret key does not end up in the Android app itself.

   Request example:

   https://smartcaptcha.yandexcloud.net/validate?secret=<server_key>&ip=<user_IP_address>&token=<token>
   

3. Get a server response. It contains a JSON object with the status and message fields.

   Here is an example:

   • It is a human:

   {
     "status": "ok",
     "message": ""
   }
   

   • It is a robot:

   {
     "status": "failed",
     "message": ""
   }