> ## Documentation Index
> Fetch the complete documentation index at: https://docs.supernote.com/llms.txt
> Use this file to discover all available pages before exploring further.

# registerPluginLifeListener

> Listen for plugin lifecycle events.

```ts theme={null}
registerPluginLifeListener(listener: PluginEventListener): PluginEventSubscription;
```

Listens for plugin lifecycle changes. When the host emits a lifecycle event, it calls `listener.onMsg(msg)`, where `msg.state` is the state value.

<Note>
  This API depends on the internal event channel registered by `init()`. Call `PluginManager.init()` first, then register the lifecycle listener.
</Note>

**Parameters**

| Parameter  | Type                  | Description                                                                               |
| ---------- | --------------------- | ----------------------------------------------------------------------------------------- |
| `listener` | `PluginEventListener` | Lifecycle listener that implements `onMsg(msg)`. `msg.state` is the lifecycle state value |

**Returns**

* `PluginEventSubscription`: subscription object. Call `remove()` to unregister the listener

**Notes**

* The callback receives the event `data`, not the full original message. Use `msg.state` to determine the current lifecycle state
* If the listener is registered after the event arrives, and the most recent lifecycle event is still within 1 second, that last event is delivered immediately so the listener does not miss it

## Lifecycle States

| `state` | Meaning                                                                                                                 |
| ------- | ----------------------------------------------------------------------------------------------------------------------- |
| `0`     | Initialized: the plugin has completed initialization. This state fires very early, so plugins usually do not receive it |
| `1`     | Mounted: the plugin has been mounted successfully                                                                       |
| `2`     | Start: the plugin is running, with its UI shown in the foreground                                                       |
| `3`     | Stop: the plugin is paused, with no UI in the foreground, but it can still run in the background                        |
| `4`     | Unmounted: the plugin's component has been unmounted; it cannot run in this state                                       |
| `5`     | Destroyed: the plugin has been destroyed                                                                                |

## Example

```ts wrap theme={null}
import { PluginManager } from 'sn-plugin-lib';

/**
 * Example: listen for plugin lifecycle events.
 */
export async function exampleRegisterPluginLifeListener() {
  await PluginManager.init();
  const sub = PluginManager.registerPluginLifeListener({
    onMsg(msg) {
      const state = msg?.state;
      console.log('plugin life state:', state);
    },
  });
  return sub;
}
```