# Manage the camera lifecycle in Flutter

> Use one NosmaiCameraPreview, rely on its app lifecycle handling, switch lenses safely, and detach the native view before navigation.

> For AI agents: the complete documentation index is at https://nosmai.com/llms/effects.txt

Product: Nosmai Effects
Group: guide
Source: https://nosmai.com/docs/effects/guides/camera/manage-camera-lifecycle/flutter/

## Prerequisites

- A working [Flutter quickstart](/docs/effects/quickstart/flutter/)
- Exactly one mounted `NosmaiCameraPreview`
- No Flutter `camera` controller owning the same device

## Use the preview owner

`NosmaiCameraPreview` handles normal application pause and resume internally.
For temporary app-owned tab transitions, the public controls are:

```dart
final nosmai = NosmaiFlutter.instance;
await nosmai.pauseCamera();
await nosmai.resumeCamera();
```

Do not call both these methods and a second camera plugin for the same screen.

## Switch the camera

Await the switch result and keep the button disabled while it is pending:

```dart
final switched = await NosmaiFlutter.instance.switchCamera();
if (!switched) return;
```

The wrapper rejects operational failures and safely ignores rapid concurrent
switches.

## Navigate away safely

Use `NosmaiCameraLifecycleMixin` when the route needs an explicit asynchronous
exit step:

```dart
await cleanupBeforeNavigation();
if (mounted) Navigator.of(context).pop();
```

The native PlatformView owns final disposal. Do not launch another global
cleanup from `State.dispose`, because it can stop a newly mounted preview.

## Verify it worked

Switch lenses, background and foreground the app, then open and close the route
ten times. Confirm one preview remains mounted, the camera indicator turns off
after exit, and returning does not create a second session.

## Common errors

| Symptom | Cause | Fix |
| --- | --- | --- |
| Camera is busy | Another plugin or duplicate preview owns the device | Dispose the old controller and keep one `NosmaiCameraPreview` |
| New screen closes immediately | Old route cleanup raced with the new PlatformView | Use `cleanupBeforeNavigation` and do not start global cleanup in `dispose` |
| Switch returns `false` | A rapid or concurrent switch was safely ignored | Keep the current lens and re-enable the control after the pending call |

## Next steps

- [Capture a processed photo in Flutter](/docs/effects/guides/output/capture-a-photo/flutter/)
- [Record processed video in Flutter](/docs/effects/guides/output/record-video/flutter/)

## References

- [Flutter API reference](/docs/effects/reference/api/flutter/)
- [Flutter package](https://pub.dev/packages/nosmai_effects_sdk)