# 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](/files/XzfVQ4NzXASQ5PvoP3dH)


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