WorldWind Kotlin/earth.worldwind.gesture/FlingAnimator

FlingAnimator

class FlingAnimator(scheduler: FrameScheduler, applyPanDelta: (deltaPxX: Double, deltaPxY: Double) -> Unit, onActiveChange: (active: Boolean) -> Unit = {})

Drives a per-frame action with monotonically decaying velocity until the velocity drops below a threshold. The platform supplies a FrameScheduler that fires a tick on each render frame (Choreographer / requestAnimationFrame / Swing Timer); each tick computes its own elapsed time so the animation stays correct even when the scheduler's interval drifts.

Used for inertial pan ("fling") after a drag/pan gesture. Distance integrates to v0 / k (linear in initial velocity) and duration is ln(v0 / vMin) / k (logarithmic) — so harder flicks travel proportionally further while still settling in roughly the same wall-clock time.

Constructors

FlingAnimator

constructor(scheduler: FrameScheduler, applyPanDelta: (deltaPxX: Double, deltaPxY: Double) -> Unit, onActiveChange: (active: Boolean) -> Unit = {})

Properties

decayPerSecond

var decayPerSecond: Double

Exponential decay rate per second. With decayPerSecond = 3.0 velocity halves every ~230 ms.

isActive

var isActive: Boolean

minVelocity

var minVelocity: Double

Velocities below this magnitude (in caller's units per millisecond) are treated as stopped.

Functions

cancel

fun cancel()

Cancels an in-progress fling. Safe to call when not active.

start

fun start(vx0: Double, vy0: Double)

Begins a fling at the given velocity. A no-op if the speed is below minVelocity.