# Listen for video events

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The Video SDK for Android fires several video-related callbacks through `ZoomVideoSDKDelegate`. Implement the delegate and override the callbacks below to react to video state changes in your session.

If you haven't already set up a delegate, see [Integrate](/docs/video-sdk/android/integrate/) for details.

## User video status

`onUserVideoStatusChanged` fires when any user starts or stops their video. Use this callback to update your UI. For example, swap a "video off" placeholder for the rendered video, or vice versa.

```kotlin
override fun onUserVideoStatusChanged(videoHelper: ZoomVideoSDKVideoHelper?, userList: MutableList<ZoomVideoSDKUser>) {
    userList.forEach { user ->
        val isOn = user.videoStatus.isOn
        // update the rendered tile or placeholder for this user
    }
}
```

```java
@Override
public void onUserVideoStatusChanged(ZoomVideoSDKVideoHelper videoHelper, List<ZoomVideoSDKUser> userList) {
    for (ZoomVideoSDKUser user : userList) {
        boolean isOn = user.getVideoStatus().isOn();
        // update the rendered tile or placeholder for this user
    }
}
```

## Spotlight list changes

`onSpotlightVideoChanged` fires whenever the spotlighted user list changes, either because a user was added to or removed from the spotlight. Use this to re-render your gallery layout (for example, to enlarge the spotlighted user's tile).

```kotlin
override fun onSpotlightVideoChanged(videoHelper: ZoomVideoSDKVideoHelper?, userList: MutableList<ZoomVideoSDKUser>) {
    // userList contains the current spotlighted users
    // re-render your gallery to reflect the new spotlight state
}
```

```java
@Override
public void onSpotlightVideoChanged(ZoomVideoSDKVideoHelper videoHelper, List<ZoomVideoSDKUser> userList) {
    // userList contains the current spotlighted users
    // re-render your gallery to reflect the new spotlight state
}
```

For more information on how to add and remove users from the spotlight, see [Spotlight a user](/docs/video-sdk/android/video/spotlight/).

## Multi-camera stream status

`onMultiCameraStreamStatusChanged` fires when a user enables, disables, mutes, or unmutes a multi-camera stream. The delegate exposes two overloads, one for the raw-data-pipe approach and one for the canvas approach.

```kotlin
override fun onMultiCameraStreamStatusChanged(
    status: ZoomVideoSDKMultiCameraStreamStatus?,
    user: ZoomVideoSDKUser?,
    videoPipe: ZoomVideoSDKRawDataPipe?
) {
    // Raw data pipe variant — see the multi-camera and raw-data docs
}

override fun onMultiCameraStreamStatusChanged(
    status: ZoomVideoSDKMultiCameraStreamStatus?,
    user: ZoomVideoSDKUser?,
    canvas: ZoomVideoSDKVideoCanvas?
) {
    // Canvas variant — subscribe a ZoomVideoSDKVideoView to the canvas to render
}
```

```java
@Override
public void onMultiCameraStreamStatusChanged(ZoomVideoSDKMultiCameraStreamStatus status,
                                             ZoomVideoSDKUser user,
                                             ZoomVideoSDKRawDataPipe videoPipe) {
    // Raw data pipe variant — see the multi-camera and raw-data docs
}

@Override
public void onMultiCameraStreamStatusChanged(ZoomVideoSDKMultiCameraStreamStatus status,
                                             ZoomVideoSDKUser user,
                                             ZoomVideoSDKVideoCanvas canvas) {
    // Canvas variant — subscribe a ZoomVideoSDKVideoView to the canvas to render
}
```

For more on how to enable, disable, mute, and unmute multi-camera streams, see [Multiple camera support](/docs/video-sdk/android/video/multiple-cameras/).

## External USB camera connected or disconnected

`onUVCCameraStatusChange` fires when an external USB Video Class (UVC) camera is plugged into or removed from the device. This is useful on tablets that support USB cameras. Surface a "new camera available" UI when a camera is connected, and refresh your camera list when one is removed.

```kotlin
override fun onUVCCameraStatusChange(cameraId: String?, status: UVCCameraStatus?) {
    // Refresh your camera list and update any settings UI
}
```

```java
@Override
public void onUVCCameraStatusChange(String cameraId, UVCCameraStatus status) {
    // Refresh your camera list and update any settings UI
}
```

## Alpha channel mode

`onVideoAlphaChannelStatusChanged` fires when alpha channel mode (transparent-background video) is toggled on or off.

```kotlin
override fun onVideoAlphaChannelStatusChanged(isAlphaModeOn: Boolean) {
    // Adjust rendering to handle transparency
}
```

```java
@Override
public void onVideoAlphaChannelStatusChanged(boolean isAlphaModeOn) {
    // Adjust rendering to handle transparency
}
```

## Video canvas subscription failure

`onVideoCanvasSubscribeFail` fires when a call to subscribe a `ZoomVideoSDKVideoView` to a user's video canvas fails. The reason is returned as a `ZoomVideoSDKVideoSubscribeFailReason`. Common failure cases include exceeding the device's render limit or attempting to subscribe before the SDK has finished initializing.

```kotlin
override fun onVideoCanvasSubscribeFail(
    failReason: ZoomVideoSDKVideoSubscribeFailReason?,
    user: ZoomVideoSDKUser?,
    view: ZoomVideoSDKVideoView?
) {
    // Surface an error in your UI, or retry after the underlying issue is resolved
}
```

```java
@Override
public void onVideoCanvasSubscribeFail(ZoomVideoSDKVideoSubscribeFailReason failReason,
                                       ZoomVideoSDKUser user,
                                       ZoomVideoSDKVideoView view) {
    // Surface an error in your UI, or retry after the underlying issue is resolved
}
```

## Camera control requests

A remote user can request control of the current user's camera. Two callbacks cover the request/response cycle.

`onCameraControlRequestReceived` fires when another user requests control. Use the `requestHandler` parameter to approve or decline.

```kotlin
override fun onCameraControlRequestReceived(
    user: ZoomVideoSDKUser?,
    requestType: ZoomVideoSDKCameraControlRequestType?,
    requestHandler: ZoomVideoSDKCameraControlRequestHandler?
) {
    // Show a confirmation dialog, then call requestHandler.approve() or .decline()
}
```

```java
@Override
public void onCameraControlRequestReceived(ZoomVideoSDKUser user,
                                           ZoomVideoSDKCameraControlRequestType requestType,
                                           ZoomVideoSDKCameraControlRequestHandler requestHandler) {
    // Show a confirmation dialog, then call requestHandler.approve() or .decline()
}
```

`onCameraControlRequestResult` fires on the requesting user's side, with the approval result.

```kotlin
override fun onCameraControlRequestResult(user: ZoomVideoSDKUser?, isApproved: Boolean) {
    // Update the UI based on whether the request was approved
}
```

```java
@Override
public void onCameraControlRequestResult(ZoomVideoSDKUser user, boolean isApproved) {
    // Update the UI based on whether the request was approved
}
```

## Canvas snapshots

`onCanvasSnapshotTaken` fires when a snapshot of a video canvas is successfully captured. `onCanvasSnapshotIncompatible` fires when a snapshot fails because the target user's stream is not compatible with snapshots.

```kotlin
override fun onCanvasSnapshotTaken(user: ZoomVideoSDKUser?, isShare: Boolean) {
    // The snapshot is ready — handle it in your UI
}

override fun onCanvasSnapshotIncompatible(user: ZoomVideoSDKUser?) {
    // Snapshot was not possible — fall back gracefully
}
```

```java
@Override
public void onCanvasSnapshotTaken(ZoomVideoSDKUser user, boolean isShare) {
    // The snapshot is ready — handle it in your UI
}

@Override
public void onCanvasSnapshotIncompatible(ZoomVideoSDKUser user) {
    // Snapshot was not possible — fall back gracefully
}
```

## Network status

For per-user video network quality changes, listen to `onUserNetworkStatusChanged` and check for the video-specific data type, or use `onUserOverallNetworkStatusChanged` for the user's overall quality across all data types.

> **Note**
>
> The dedicated `onUserVideoNetworkStatusChanged` callback is deprecated in favor of the more general `onUserNetworkStatusChanged` and `onUserOverallNetworkStatusChanged` callbacks.