> 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}',
        );
      }
    });
  }
```


---

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