IOSScrollViewFlingVelocityTracker class
A VelocityTracker subclass that provides a close approximation of iOS scroll view's velocity estimation strategy.
The estimated velocity reported by this class is a close approximation of the velocity an iOS scroll view would report with the same PointerMoveEvents, when the touch that initiates a fling is released.
This class differs from the VelocityTracker class in that it uses weighted average of the latest few velocity samples of the tracked pointer, instead of doing a linear regression on a relatively large amount of data points, to estimate the velocity of the tracked pointer. Adding data points and estimating the velocity are both cheap.
To obtain a velocity, call getVelocity or getVelocityEstimate. The
estimated velocity is typically used as the initial flinging velocity of a
Scrollable, when its drag gesture ends.
See also:
- scrollViewWillEndDragging(_:withVelocity:targetContentOffset:), the iOS method that reports the fling velocity when the touch is released.
- Inheritance
-
- Object
- VelocityTracker
- IOSScrollViewFlingVelocityTracker
- Implementers
Constructors
- IOSScrollViewFlingVelocityTracker(PointerDeviceKind kind)
- Create a new IOSScrollViewFlingVelocityTracker.
Properties
- hashCode → int
-
The hash code for this object.
no setterinherited
- kind → PointerDeviceKind
-
The kind of pointer this tracker is for.
finalinherited
- runtimeType → Type
-
A representation of the runtime type of the object.
no setterinherited
Methods
-
addPosition(
Duration time, Offset position) → void -
Adds a position as the given time to the tracker.
override
-
getVelocity(
) → Velocity -
Computes the velocity of the pointer at the time of the last
provided data point.
inherited
-
getVelocityEstimate(
) → VelocityEstimate -
Returns an estimate of the velocity of the object being tracked by the
tracker given the current information available to the tracker.
override
-
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a nonexistent method or property is accessed.
inherited
-
toString(
) → String -
A string representation of this object.
inherited
Operators
-
operator ==(
Object other) → bool -
The equality operator.
inherited