ScrollPositionWithSingleContext class Null safety

A scroll position that manages scroll activities for a single ScrollContext.

This class is a concrete subclass of ScrollPosition logic that handles a single ScrollContext, such as a Scrollable. An instance of this class manages ScrollActivity instances, which change what content is visible in the Scrollable's Viewport.

See also:

Inheritance
Implemented types

Constructors

ScrollPositionWithSingleContext({required ScrollPhysics physics, required ScrollContext context, double? initialPixels = 0.0, bool keepScrollOffset = true, ScrollPosition? oldPosition, String? debugLabel})
Create a ScrollPosition object that manages its behavior using ScrollActivity objects. [...]

Properties

activity ScrollActivity?
The currently operative ScrollActivity. [...]
@protected, @visibleForTesting, read-only, inherited
allowImplicitScrolling bool
Whether a viewport is allowed to change pixels implicitly to respond to a call to RenderObject.showOnScreen. [...]
read-only, inherited
atEdge bool
Whether the pixels value is exactly at the minScrollExtent or the maxScrollExtent.
read-only, inherited
axis Axis
The axis in which the scroll view scrolls.
read-only, inherited
axisDirection AxisDirection
The direction in which the scroll view scrolls.
read-only, override
context ScrollContext
Where the scrolling is taking place. [...]
final, inherited
debugLabel String?
A label that is used in the toString output. [...]
final, inherited
extentAfter double
The quantity of content conceptually "below" the viewport in the scrollable. This is the content below the content described by extentInside.
read-only, inherited
extentBefore double
The quantity of content conceptually "above" the viewport in the scrollable. This is the content above the content described by extentInside.
read-only, inherited
extentInside double
The quantity of content conceptually "inside" the viewport in the scrollable. [...]
read-only, inherited
hasContentDimensions bool
Whether the minScrollExtent and the maxScrollExtent properties are available.
read-only, inherited
hashCode int
The hash code for this object. [...]
read-only, inherited
hasListeners bool
Whether any listeners are currently registered. [...]
@protected, read-only, inherited
hasPixels bool
Whether the pixels property is available.
read-only, inherited
hasViewportDimension bool
Whether the viewportDimension property is available.
read-only, inherited
haveDimensions bool
Whether viewportDimension, minScrollExtent, maxScrollExtent, outOfRange, and atEdge are available. [...]
read-only, inherited
isScrollingNotifier ValueNotifier<bool>
This notifier's value is true if a scroll is underway and false if the scroll position is idle. [...]
final, inherited
keepScrollOffset bool
Save the current scroll offset with PageStorage and restore it if this scroll position's scrollable is recreated. [...]
final, inherited
maxScrollExtent double
The maximum in-range value for pixels. [...]
read-only, inherited
minScrollExtent double
The minimum in-range value for pixels. [...]
read-only, inherited
outOfRange bool
Whether the pixels value is outside the minScrollExtent and maxScrollExtent.
read-only, inherited
physics ScrollPhysics
How the scroll position should respond to user input. [...]
final, inherited
pixels double
The number of pixels to offset the children in the opposite of the axis direction. [...]
read-only, inherited
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited
userScrollDirection ScrollDirection
The direction in which the user is trying to change pixels, relative to the viewport's RenderViewportBase.axisDirection. [...]
read-only, override
viewportDimension double
The extent of the viewport along the axisDirection.
read-only, inherited

Methods

absorb(ScrollPosition other) → void
Take any current applicable state from the given ScrollPosition. [...]
override
addListener(VoidCallback listener) → void
Register a closure to be called when the object changes. [...]
inherited
animateTo(double to, {required Duration duration, required Curve curve}) Future<void>
Animates the position from its current value to the given value. [...]
override
applyBoundaryConditions(double value) double
Returns the overscroll by applying the boundary conditions. [...]
@protected, inherited
applyContentDimensions(double minScrollExtent, double maxScrollExtent) bool
Called when the viewport's content extents are established. [...]
inherited
applyNewDimensions() → void
Notifies the activity that the dimensions of the underlying viewport or contents have changed. [...]
override
applyUserOffset(double delta) → void
Updates the scroll position by the given amount. [...]
override
applyViewportDimension(double viewportDimension) bool
Called when the viewport's extents are established. [...]
inherited
beginActivity(ScrollActivity? newActivity) → void
Change the current activity, disposing of the old one and sending scroll notifications as necessary. [...]
override
copyWith({double? minScrollExtent, double? maxScrollExtent, double? pixels, double? viewportDimension, AxisDirection? axisDirection}) ScrollMetrics
Creates a ScrollMetrics that has the same properties as this object. [...]
inherited
correctBy(double correction) → void
Apply a layout-time correction to the scroll offset. [...]
inherited
correctForNewDimensions(ScrollMetrics oldPosition, ScrollMetrics newPosition) bool
Verifies that the new content and viewport dimensions are acceptable. [...]
@protected, inherited
correctPixels(double value) → void
Change the value of pixels to the new value, without notifying any customers. [...]
inherited
debugFillDescription(List<String> description) → void
Add additional information to the given description for use by toString. [...]
override
didEndScroll() → void
Called by beginActivity to report when an activity has ended. [...]
inherited
didOverscrollBy(double value) → void
Called by setPixels to report overscroll when an attempt is made to change the pixels position. Overscroll is the amount of change that was not applied to the pixels value.
inherited
didStartScroll() → void
Called by beginActivity to report when an activity has started.
inherited
didUpdateScrollDirection(ScrollDirection direction) → void
Dispatches a notification that the userScrollDirection has changed. [...]
inherited
didUpdateScrollMetrics() → void
Dispatches a notification that the ScrollMetrics have changed.
inherited
didUpdateScrollPositionBy(double delta) → void
Called by setPixels to report a change to the pixels position.
inherited
dispose() → void
Discards any resources used by the object. After this is called, the object is not in a usable state and should be discarded (calls to addListener and removeListener will throw after the object is disposed). [...]
override
drag(DragStartDetails details, VoidCallback dragCancelCallback) Drag
Start a drag activity corresponding to the given DragStartDetails. [...]
override
ensureVisible(RenderObject object, {double alignment = 0.0, Duration duration = Duration.zero, Curve curve = Curves.ease, ScrollPositionAlignmentPolicy alignmentPolicy = ScrollPositionAlignmentPolicy.explicit, RenderObject? targetRenderObject}) Future<void>
Animates the position such that the given object is as visible as possible by just scrolling this position. [...]
inherited
forcePixels(double value) → void
Change the value of pixels to the new value, and notify any customers, but without honoring normal conventions for changing the scroll offset. [...]
@protected, inherited
goBallistic(double velocity) → void
Start a physics-driven simulation that settles the pixels position, starting at a particular velocity. [...]
override
goIdle() → void
Terminate the current activity and start an idle activity.
override
hold(VoidCallback holdCancelCallback) ScrollHoldController
Stop the current activity and start a HoldScrollActivity.
override
jumpTo(double value) → void
Jumps the scroll position from its current value to the given value, without animation, and without checking if the new value is in range. [...]
override
jumpToWithoutSettling(double value) → void
Deprecated. Use jumpTo or a custom ScrollPosition instead.
@Deprecated('This will lead to bugs.'), override
moveTo(double to, {Duration? duration, Curve? curve, bool? clamp = true}) Future<void>
Calls jumpTo if duration is null or Duration.zero, otherwise animateTo is called. [...]
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
inherited
notifyListeners() → void
Call all the registered listeners. [...]
inherited
pointerScroll(double delta) → void
Changes the scrolling position based on a pointer signal from current value to delta without animation and without checking if new value is in range, taking min/max scroll extent into account. [...]
override
recommendDeferredLoading(BuildContext context) bool
Provides a heuristic to determine if expensive frame-bound tasks should be deferred. [...]
inherited
removeListener(VoidCallback listener) → void
Remove a previously registered closure from the list of closures that are notified when the object changes. [...]
inherited
restoreOffset(double offset, {bool initialRestore = false}) → void
Called by context to restore the scroll offset to the provided value. [...]
inherited
restoreScrollOffset() → void
Called whenever the ScrollPosition is created, to restore the scroll offset if possible. [...]
@protected, inherited
saveOffset() → void
Called whenever scrolling ends, to persist the current scroll offset for state restoration purposes. [...]
@protected, inherited
saveScrollOffset() → void
Called whenever scrolling ends, to store the current scroll offset in a storage mechanism with a lifetime that matches the app's lifetime. [...]
@protected, inherited
setPixels(double newPixels) double
Update the scroll position (pixels) to a given pixel value. [...]
override
toString() String
A string representation of this object. [...]
inherited
updateUserScrollDirection(ScrollDirection value) → void
Set userScrollDirection to the given value. [...]

Operators

operator ==(Object other) bool
The equality operator. [...]
inherited