# Extend the default Unity activity

> Override basic interactions between the Android operating system and the Unity Android application.

The `UnityPlayerActivity` of a Unity Android application is responsible for basic interactions between the Android operating system and the application. You can use plug-ins to create your own [Activity](https://developer.android.com/reference/android/app/Activity.html) that extends and overrides Unity's default `UnityPlayerActivity`.

**Notes**:

* If you're creating a custom activity with GameActivity application entry point, you need to extend the `UnityPlayerGameActivity` class.
* `UnityPlayerActivity` and `UnityPlayerGameActivity` use the `UnityPlayerForActivityOrService` and `UnityPlayerForGameActivity` bridge classes respectively. Unity splits these bridge classes from the `UnityPlayer` Java class. To create a custom activity, extend `UnityPlayerActivity` or `UnityPlayerGameActivity` and not the bridge classes. If your activity code references the `UnityPlayer` class directly, rename it to the relevant bridge class to avoid compile errors.

| **Topic**                                                                                                                                                                                      | **Description**                                                                      |
| ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------ |
| [Create a custom activity](/engine/6000.3/manual/platform-specific/android/developing/application-entries/activity/unity-player-activity/custom-activity.md)                                   | Extend the default Unity activity to control interactions between Unity and Android. |
| [Specify Android Player command-line arguments](/engine/6000.3/manual/platform-specific/android/developing/application-entries/activity/unity-player-activity/custom-activity-command-line.md) | Specify startup command-line arguments to pass to Unity.                             |

## Additional resources

* [Android plug-ins](/engine/6000.3/manual/platform-specific/android/developing/plugins-for.md)