# CustomActivity

### Introduction

CustomActivity is a function which is part of every Screen and Entity. This is where you can place code that you would like to run every-frame. Examples of common logic in CustomActivity include:

* Collision
* Input
* Checking for non-UI events such as a timer ending a level

CustomActivity is called by default by generated code, so it should never be called in custom code.

### Order of CustomActivity

A Screen's CustomActivity will always be called last relative to the Objects inside of it. More generally speaking, the children Objects of a Screen or Entity will have their CustomActivity called before the parent container. Objects in a Screen or Entity will have their CustomActivity called in the order in which they appear in Glue. In this example, the order of CustomActivity will be as follows:

1. SubEntityInstance
2. SubEntityInstance2
3. SubEntityInstance3
4. TestEntity
5. Whatever contains TestEntity (like a Screen)

![SampleHierarchy.PNG](https://951240982-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M_fye9Ufg3vzJxwX5Hk%2Fuploads%2Fgit-blob-bcd44c3c6f65e20514fa77e024fe65101571e8ee%2Fmigrated_media-SampleHierarchy.PNG?alt=media)