> 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/faceliveness/lifecycle.md).

# SDK Lifecycle

## CafLivenessListener (Flutter)

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

| **Event**                       | **Description**                                                                                     |
| ------------------------------- | --------------------------------------------------------------------------------------------------- |
| **FaceLivenessEventConnecting** | Indicates the SDK is initializing or connecting to the server.                                      |
| **FaceLivenessEventConnected**  | Triggered when the SDK is fully connected, and the user interface will be displayed.                |
| **FaceLivenessEventClosed**     | Triggered when the user cancels the liveness detection process.                                     |
| **FaceLivenessEventSuccess**    | Triggered upon successful liveness detection, providing the result in `signedResponse`.             |
| **FaceLivenessEventFailure**    | Called when an SDK failure occurs, providing error details like `errorType` and `errorDescription`. |

### Example Implementation

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

```dart
void _setupFaceLivenessListener(Stream<FaceLivenessEvent> stream) {
  stream.listen((event) {
    if (event is FaceLivenessEventConnecting) {
      print('Connecting to FaceLiveness...');
    } else if (event is FaceLivenessEventConnected) {
      print('Connected to FaceLiveness.');
    } else if (event is FaceLivenessEventClosed) {
      print('SDK closed by the user.');
    } else if (event is FaceLivenessEventSuccess) {
      print('Success! SignedResponse: ${event.signedResponse}');
    } else if (event is FaceLivenessEventFailure) {
      print(
        'Failure! Error type: ${event.errorType}, '
        'Error description: ${event.errorDescription}',
      );
    }
  });
}
```


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