PointerInputChange - Class in Compose UI

Class

Common

class PointerInputChange(
    val id: PointerId,
    val uptimeMillis: Long,
    val position: Offset,
    val pressed: Boolean,
    val pressure: Float,
    val previousUptimeMillis: Long,
    val previousPosition: Offset,
    val previousPressed: Boolean,
    isInitiallyConsumed: Boolean,
    val type: PointerType = PointerType.Touch,
    val scrollDelta: Offset = Offset.Zero,
    val scaleFactor: Float = 1f,
    val panOffset: Offset = Offset.Zero,
)

Describes a change that has occurred for a particular pointer, as well as how much of the change has been consumed (meaning, used by a node in the UI).

The position represents the position of the pointer relative to the element that this PointerInputChange is being dispatched to.

Note 1: A PointerEvent's PointerEventType is the cause of an event and the associated PointerInputChange's properties reflecting that. Most of those are exclusive, in other words, a Press/Release PointerEventType will not cause a scrollDelta change and a Scroll PointerEventType will not cause a pressed or previousPressed change. However, either a a Scroll or a Press/Release may contain a position change in its PointerInputChanges. (You can imagine one finger moving while another is lifted up.)

Examples of PointerEventType and the associated PointerInputChange property changes:

Press -> press will change (position may change) but scroll delta will not.
Release -> press will change (position may change) but scroll delta will not.
Move -> position will change but press and scroll delta will not.
Scroll -> scroll delta will change (position may change) but press will not.

Note 2: The position values can be outside the actual bounds of the element itself meaning the numbers can be negative or larger than the element bounds.

The previousPosition represents the position of the pointer offset to the current position of the pointer relative to the screen.

This means that position and previousPosition can always be used to understand how much a pointer has moved relative to an element, even if that element is moving along with the changes to the pointer. For example, if a pointer touches a 1x1 pixel box in the middle, position will report a position of (0, 0) when dispatched to it. If the next event moves x position 5 pixels, position will report (5, 0) and previousPosition will report (0, 0). If the box moves all 5 pixels, and the next event represents the pointer moving along the x axis for 5 more pixels, position will again report (5, 0) and previousPosition will report (0, 0).

Parameters


id	The unique id of the pointer associated with this `PointerInputChange`.
uptimeMillis	The time of the current pointer event, in milliseconds. The start (`0`) time is platform-dependent
position	The `Offset` of the current pointer event, relative to the containing element (values can be negative or larger than the element bounds).
pressed	`true` if the pointer event is considered "pressed." For example, finger touching the screen or a mouse button is pressed `pressed` would be `true`.
pressure	The pressure of the of the pointer event
previousUptimeMillis	The `uptimeMillis` of the previous pointer event
previousPosition	The `Offset` of the previous pointer event, offset to the `position` and relative to the containing element.
previousPressed	`true` if the pointer event was considered "pressed." For example , if a finger was touching the screen or a mouse button was pressed, `previousPressed` would be `true`.
isInitiallyConsumed	whether the change was consumed from the start or not. This value can change over time as change is propagated through the pointer handlers. To query the actual status of the change use `isConsumed`
type	The device type that produced the event, such as `mouse`, or `touch`.
scrollDelta	The amount of scroll wheel movement in the horizontal and vertical directions. Note that this is not an offset in pixel coordinates, but is instead an offset in a platform specific mouse wheel tick units. Also consider handling `panOffset`, which represents a similar action from trackpads.
scaleFactor	A multiplicative scale factor indicating the amount of scale to perform as part of this pointer input change. A value of `1f` indicates no scale, a value less than `1f` indicates a scale down, commonly causing a zoom out, and a value greater than `1f` indicates a scale up, commonly causing a zoom in.
panOffset	An `Offset` in pixel coordinates indicating an amount of panning. Also consider handling `scrollDelta`, which represents a similar action from mouse wheels.

Secondary Constructors

constructor(
    id: PointerId,
    uptimeMillis: Long,
    position: Offset,
    pressed: Boolean,
    previousUptimeMillis: Long,
    previousPosition: Offset,
    previousPressed: Boolean,
    isInitiallyConsumed: Boolean,
    type: PointerType = PointerType.Touch,
    scrollDelta: Offset = Offset.Zero,
    scaleFactor: Float = 1f,
    panOffset: Offset = Offset.Zero,
) : this(
    id = id,
    uptimeMillis = uptimeMillis,
    position = position,
    pressed = pressed,
    pressure = 1.0f,
    previousUptimeMillis = previousUptimeMillis,
    previousPosition = previousPosition,
    previousPressed = previousPressed,
    isInitiallyConsumed = isInitiallyConsumed,
    type = type,
    scrollDelta = scrollDelta,
    scaleFactor = scaleFactor,
    panOffset = panOffset,
)

constructor(
    id: PointerId,
    uptimeMillis: Long,
    position: Offset,
    pressed: Boolean,
    pressure: Float,
    previousUptimeMillis: Long,
    previousPosition: Offset,
    previousPressed: Boolean,
    isInitiallyConsumed: Boolean,
    type: PointerType = PointerType.Touch,
    scrollDelta: Offset = Offset.Zero,
) : this(
    id = id,
    uptimeMillis = uptimeMillis,
    position = position,
    pressed = pressed,
    pressure = pressure,
    previousUptimeMillis = previousUptimeMillis,
    previousPosition = previousPosition,
    previousPressed = previousPressed,
    isInitiallyConsumed = isInitiallyConsumed,
    type = type,
    scrollDelta = scrollDelta,
)

constructor(
    id: PointerId,
    uptimeMillis: Long,
    position: Offset,
    pressed: Boolean,
    previousUptimeMillis: Long,
    previousPosition: Offset,
    previousPressed: Boolean,
    isInitiallyConsumed: Boolean,
    type: PointerType = PointerType.Touch,
    scrollDelta: Offset = Offset.Zero,
) : this(
    id = id,
    uptimeMillis = uptimeMillis,
    position = position,
    pressed = pressed,
    previousUptimeMillis = previousUptimeMillis,
    previousPosition = previousPosition,
    previousPressed = previousPressed,
    isInitiallyConsumed = isInitiallyConsumed,
    type = type,
    scrollDelta = scrollDelta,
)

constructor(
    id: PointerId,
    uptimeMillis: Long,
    position: Offset,
    pressed: Boolean,
    previousUptimeMillis: Long,
    previousPosition: Offset,
    previousPressed: Boolean,
    consumed: ConsumedData,
    type: PointerType = PointerType.Touch,
) : this(
    id,
    uptimeMillis,
    position,
    pressed,
    pressure = 1.0f,
    previousUptimeMillis,
    previousPosition,
    previousPressed,
    consumed.downChange || consumed.positionChange,
    type,
    Offset.Zero,
)

internal constructor(
    id: PointerId,
    uptimeMillis: Long,
    position: Offset,
    pressed: Boolean,
    pressure: Float,
    previousUptimeMillis: Long,
    previousPosition: Offset,
    previousPressed: Boolean,
    isInitiallyConsumed: Boolean,
    type: PointerType,
    historical: List<HistoricalChange>,
    scrollDelta: Offset,
    scaleFactor: Float,
    panOffset: Offset,
    originalEventPosition: Offset,
) : this(
    id = id,
    uptimeMillis = uptimeMillis,
    position = position,
    pressed = pressed,
    pressure = pressure,
    previousUptimeMillis = previousUptimeMillis,
    previousPosition = previousPosition,
    previousPressed = previousPressed,
    isInitiallyConsumed = isInitiallyConsumed,
    type = type,
    scrollDelta = scrollDelta,
    scaleFactor = scaleFactor,
    panOffset = panOffset,
) {
    _historical = historical
    this.originalEventPosition = originalEventPosition
}

Properties

Common

val historical: List<HistoricalChange>

Optional high-frequency pointer moves in between the last two dispatched events. Can be used for extra accuracy when input rate exceeds framerate.

Common

val isConsumed: Boolean

Indicates whether the change was consumed or not. Note that the change must be consumed in full as there's no partial consumption system provided.

Common

Deprecated use isConsumed and consume() pair of methods instead

val consumed: ConsumedData

Functions

fun consume()

Consume change event, claiming all the corresponding change info to the caller. This is usually needed when, button, when being clicked, consumed the "up" event so no other parents of this button could consume this "up" again.

"Consumption" is just an indication of the claim and each pointer input handler implementation must manually check this flag to respect it.

fun copy(
        id: PointerId = this.id,
        currentTime: Long = this.uptimeMillis,
        currentPosition: Offset = this.position,
        currentPressed: Boolean = this.pressed,
        previousTime: Long = this.previousUptimeMillis,
        previousPosition: Offset = this.previousPosition,
        previousPressed: Boolean = this.previousPressed,
        consumed: ConsumedData = this.consumed,
        type: PointerType = this.type,
    ): PointerInputChange

fun copy(
        id: PointerId = this.id,
        currentTime: Long = this.uptimeMillis,
        currentPosition: Offset = this.position,
        currentPressed: Boolean = this.pressed,
        previousTime: Long = this.previousUptimeMillis,
        previousPosition: Offset = this.previousPosition,
        previousPressed: Boolean = this.previousPressed,
        type: PointerType = this.type,
        scrollDelta: Offset = this.scrollDelta,
    ): PointerInputChange