ScrollPhysics class

Determines the physics of a Scrollable widget.

For example, determines how the Scrollable will behave when the user reaches the maximum scroll extent or when the user stops scrolling.

When starting a physics Simulation, the current scroll position and velocity are used as the initial conditions for the particle in the simulation. The movement of the particle in the simulation is then used to determine the scroll position for the widget.

Instead of creating your own subclasses, parent can be used to combine ScrollPhysics objects of different types to get the desired scroll physics. For example:

const BouncingScrollPhysics(parent: AlwaysScrollableScrollPhysics())

You can also use applyTo, which is useful when you already have an instance of ScrollPhysics:

ScrollPhysics physics = const BouncingScrollPhysics();
// ...
final ScrollPhysics mergedPhysics = physics.applyTo(const AlwaysScrollableScrollPhysics());

When implementing a subclass, you must override applyTo so that it returns an appropriate instance of your subclass. Otherwise, classes like Scrollable that inform a ScrollPosition will combine them with the default ScrollPhysics object instead of your custom subclass.



ScrollPhysics({ScrollPhysics? parent})
Creates an object with the default scroll physics.


allowImplicitScrolling bool
Whether a viewport is allowed to change its scroll position implicitly in response to a call to RenderObject.showOnScreen.
no setter
allowUserScrolling bool
Whether a viewport is allowed to change the scroll position as the result of user input.
no setter
dragStartDistanceMotionThreshold double?
The minimum amount of pixel distance drags must move by to start motion the first time or after each time the drag motion stopped.
no setter
hashCode int
The hash code for this object.
no setterinherited
maxFlingVelocity double
Scroll fling velocity magnitudes will be clamped to this value.
no setter
minFlingDistance double
The minimum distance an input pointer drag must have moved to be considered a scroll fling gesture.
no setter
minFlingVelocity double
The minimum velocity for an input pointer drag to be considered a scroll fling.
no setter
parent ScrollPhysics?
If non-null, determines the default behavior for each method.
runtimeType Type
A representation of the runtime type of the object.
no setterinherited
spring SpringDescription
The spring to use for ballistic simulations.
no setter
tolerance Tolerance
Deprecated. Call toleranceFor instead.
no setter


adjustPositionForNewDimensions({required ScrollMetrics oldPosition, required ScrollMetrics newPosition, required bool isScrolling, required double velocity}) double
Describes what the scroll position should be given new viewport dimensions.
applyBoundaryConditions(ScrollMetrics position, double value) double
Determines the overscroll by applying the boundary conditions.
applyPhysicsToUserOffset(ScrollMetrics position, double offset) double
Used by DragScrollActivity and other user-driven activities to convert an offset in logical pixels as provided by the DragUpdateDetails into a delta to apply (subtract from the current position) using ScrollActivityDelegate.setPixels.
applyTo(ScrollPhysics? ancestor) ScrollPhysics
Combines this ScrollPhysics instance with the given physics.
buildParent(ScrollPhysics? ancestor) ScrollPhysics?
If parent is null then return ancestor, otherwise recursively build a ScrollPhysics that has ancestor as its parent.
carriedMomentum(double existingVelocity) double
Returns the velocity carried on repeated flings.
createBallisticSimulation(ScrollMetrics position, double velocity) Simulation?
Returns a simulation for ballistic scrolling starting from the given position with the given velocity.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
recommendDeferredLoading(double velocity, ScrollMetrics metrics, BuildContext context) bool
Provides a heuristic to determine if expensive frame-bound tasks should be deferred.
shouldAcceptUserOffset(ScrollMetrics position) bool
Whether the scrollable should let the user adjust the scroll offset, for example by dragging. If allowUserScrolling is false, the scrollable will never allow user input to change the scroll position.
toleranceFor(ScrollMetrics metrics) Tolerance
The tolerance to use for ballistic simulations.
toString() String
A string representation of this object.


operator ==(Object other) bool
The equality operator.