---
title: "VelocityTracker"
description: "Calculates the velocity of a pointer based on tracked pointer events or positions and timestamps.
VelocityTracker is platform-specific, so the output result may vary depending on the platform.

The input data is provided by calling [addPosition] or [addPointerInputChange]. Adding data is
cheap.

To obtain a velocity, call [calculateVelocity]. This will compute the velocity based on the data
added so far. Only call this when you need to use the velocity, as it is comparatively expensive.

The quality of the velocity estimation will be better if more data points have been received."
type: "class"
---

<div class='type'>Class</div>


<a id='references'></a>

<div class='sourceset sourceset-common'>Common</div>


```kotlin
class VelocityTracker
```


Calculates the velocity of a pointer based on tracked pointer events or positions and timestamps.
VelocityTracker is platform-specific, so the output result may vary depending on the platform.

The input data is provided by calling `addPosition` or `addPointerInputChange`. Adding data is
cheap.

To obtain a velocity, call `calculateVelocity`. This will compute the velocity based on the data
added so far. Only call this when you need to use the velocity, as it is comparatively expensive.

The quality of the velocity estimation will be better if more data points have been received.


## Functions

```kotlin
fun addPosition(timeMillis: Long, position: Offset) =
        platformVelocityTracker.addPosition(timeMillis, position)
```


Adds a position at the given time to the tracker.

Call `resetTracking` to remove added `Offset`s.


```kotlin
fun calculateVelocity(): Velocity
```


Computes the estimated velocity of the pointer at the time of the last provided data point.

The velocity calculated will not be limited. Unlike `calculateVelocity(maximumVelocity)` the
resulting velocity won't be limited.

This can be expensive. Only call this when you need the velocity.


```kotlin
fun calculateVelocity(maximumVelocity: Velocity): Velocity
```


Computes the estimated velocity of the pointer at the time of the last provided data point.

The method allows specifying the maximum absolute value for the calculated velocity. If the
absolute value of the calculated velocity exceeds the specified maximum, the return value
will be clamped down to the maximum. For example, if the absolute maximum velocity is
specified as "20", a calculated velocity of "25" will be returned as "20", and a velocity of
"-30" will be returned as "-20".

#### Parameters

| | |
| --- | --- |
| maximumVelocity | the absolute values of the X and Y maximum velocities to be returned in units/second. `units` is the units of the positions provided to this VelocityTracker. |



```kotlin
fun resetTracking() = platformVelocityTracker.resetTracking()
```


Clears the tracked positions added by `addPosition`.