> For the complete documentation index, see [llms.txt](https://docs.caf.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.caf.io/caf-sdk/flutter/standalone-modules/faceauthenticator/lifecycle.md).

# SDK Lifecycle

## CafLivenessListener (Flutter)

The `CafLivenessListener` in Flutter handles key events during the SDK's liveness detection process. Below are the correct Flutter events you can listen to:

| **Event**                   | **Description**                                                                                     |
| --------------------------- | --------------------------------------------------------------------------------------------------- |
| **FaceAuthEventClosed**     | Triggered when the user cancels the liveness detection process.                                     |
| **FaceAuthEventFailure**    | Called when an SDK failure occurs, providing error details like `errorType` and `errorDescription`. |
| **FaceAuthEventConnected**  | Triggered when the SDK is fully loaded and ready to start.                                          |
| **FaceAuthEventConnecting** | Indicates the SDK is initializing or in the process of loading.                                     |
| **FaceAuthEventSuccess**    | Triggered upon successful liveness detection, with the result available in `signedResponse`.        |

### Example Implementation

Below is an example of how to handle `CafLivenessListener` events in Flutter:

```dart
  void _setupFaceAuthListener(Stream<FaceAuthEvent> stream) {
    stream.listen((event) {
      if (event is FaceAuthEventConnecting) {
        print('Connecting to FaceAuth...');
      } else if (event is FaceAuthEventConnected) {
        print('Connected to FaceAuth.');
      } else if (event is FaceAuthEventClosed) {
        print('SDK closed by the user.');
      } else if (event is FaceAuthEventSuccess) {
        print('Success! SignedResponse: ${event.signedResponse}');
      } else if (event is FaceAuthEventFailure) {
        print(
          'Failure! Error type: ${event.errorType}, '
              'Error description: ${event.errorDescription}',
        );
      }
    });
  }
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.caf.io/caf-sdk/flutter/standalone-modules/faceauthenticator/lifecycle.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.