---
title: "CAnimationVariableChangeHandler Class"
ms.date: "11/04/2016"
f1_keywords: ["CAnimationVariableChangeHandler", "AFXANIMATIONCONTROLLER/CAnimationVariableChangeHandler", "AFXANIMATIONCONTROLLER/CAnimationVariableChangeHandler::OnValueChanged", "AFXANIMATIONCONTROLLER/CAnimationVariableChangeHandler::SetAnimationController"]
helpviewer_keywords: ["CAnimationVariableChangeHandler [MFC], OnValueChanged", "CAnimationVariableChangeHandler [MFC], SetAnimationController"]
ms.assetid: 2ea4996d-5c04-4dfc-be79-d42d55050795
---
# CAnimationVariableChangeHandler Class

Implements a callback, which is called by the Animation API when the value of an animation variable changes.

## Syntax

```
class CAnimationVariableChangeHandler : public CUIAnimationVariableChangeHandlerBase<CAnimationVariableChangeHandler>;
```

## Members

### Public Constructors

|Name|Description|
|----------|-----------------|
|`CAnimationVariableChangeHandler::CAnimationVariableChangeHandler`|Constructs a `CAnimationVariableChangeHandler` object.|

### Public Methods

|Name|Description|
|----------|-----------------|
|`CAnimationVariableChangeHandler::CreateInstance`|Creates an instance of `CAnimationVariableChangeHandler` object.|
|[CAnimationVariableChangeHandler::OnValueChanged](#onvaluechanged)|Called when a value of an animation variable has changed. (Overrides `CUIAnimationVariableChangeHandlerBase::OnValueChanged`.)|
|[CAnimationVariableChangeHandler::SetAnimationController](#setanimationcontroller)|Stores a pointer to animation controller to route events.|

## Remarks

This event handler is created and passed to `IUIAnimationVariable::SetVariableChangeHandler` method, when you call `CAnimationVariable::EnableValueChangedEvent` or `CAnimationBaseObject::EnableValueChangedEvent` (which enables this event for all animation variables encapsulated in an animation object).

## Inheritance Hierarchy

`CUIAnimationCallbackBase`

`CUIAnimationVariableChangeHandlerBase`

`CAnimationVariableChangeHandler`

## Requirements

**Header:** afxanimationcontroller.h

##  <a name="onvaluechanged"></a>  CAnimationVariableChangeHandler::OnValueChanged

Called when a value of an animation variable has changed.

```
IFACEMETHOD(OnValueChanged) (
    __in IUIAnimationStoryboard* storyboard,
    __in IUIAnimationVariable* variable,
    __in DOUBLE newValue,
    __in DOUBLE previousValue);
```

### Parameters

*storyboard*<br/>
The storyboard that is animating the variable.

*variable*<br/>
The animation variable that was updated.

*newValue*<br/>
The new value.

*previousValue*<br/>
The previous value.

### Return Value

If the method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

##  <a name="setanimationcontroller"></a>  CAnimationVariableChangeHandler::SetAnimationController

Stores a pointer to animation controller to route events.

```
void SetAnimationController(CAnimationController* pAnimationController);
```

### Parameters

*pAnimationController*<br/>
A pointer to animation controller, which will receive events.

## See Also

[Classes](../../mfc/reference/mfc-classes.md)