RenderSliverPersistentHeader class

A base class for slivers that have a RenderBox child which scrolls normally, except that when it hits the leading edge (typically the top) of the viewport, it shrinks to a minimum size (minExtent).

This class primarily provides helpers for managing the child, in particular:

  • layoutChild, which applies min and max extents and a scroll offset to lay out the child. This is normally called from performLayout.

  • childExtent, to convert the child's box layout dimensions to the sliver geometry model.

  • hit testing, painting, and other details of the sliver protocol.

Subclasses must implement performLayout, minExtent, and maxExtent, and typically also will implement updateChild.

Inheritance
Mixed in types
Implementers

Constructors

RenderSliverPersistentHeader({RenderBox child })
Creates a sliver that changes its size when scrolled to the start of the viewport. [...]

Properties

childExtent → double
The dimension of the child in the main axis.
@protected, read-only
excludeFromSemanticsScrolling ↔ bool
Whether the SemanticsNodes associated with this RenderSliver should be excluded from the semantic scrolling area. [...]
@protected, read / write
maxExtent → double
The biggest that this render object can become, in the main axis direction. [...]
read-only
minExtent → double
The smallest that this render object can become, in the main axis direction. [...]
read-only
alwaysNeedsCompositing → bool
Whether this render object always needs compositing. [...]
@protected, read-only, inherited
attached → bool
Whether this node is in a tree whose root is attached to something. [...]
read-only, inherited
centerOffsetAdjustment → double
For a center sliver, the distance before the absolute zero scroll offset that this sliver can cover. [...]
read-only, inherited
child ↔ RenderBox
The render object's unique child
read / write, inherited
constraints → SliverConstraints
The layout constraints most recently supplied by the parent.
read-only, inherited
debugCanParentUseSize → bool
Whether the parent render object is permitted to use this render object's size. [...]
read-only, inherited
debugCreator ↔ dynamic
The object responsible for creating this render object. [...]
read / write, inherited
debugDoingThisLayout → bool
Whether performLayout for this render object is currently running. [...]
read-only, inherited
debugDoingThisPaint → bool
Whether paint for this render object is currently running. [...]
read-only, inherited
debugDoingThisResize → bool
Whether performResize for this render object is currently running. [...]
read-only, inherited
debugLayer → OffsetLayer
In debug mode, the compositing layer that this render object uses to repaint. [...]
read-only, inherited
debugNeedsLayout → bool
Whether this render object's layout information is dirty. [...]
read-only, inherited
debugNeedsPaint → bool
Whether this render object's paint information is dirty. [...]
read-only, inherited
debugSemantics → SemanticsNode
The semantics of this render object. [...]
read-only, inherited
depth → int
The depth of this node in the tree. [...]
read-only, inherited
geometry ↔ SliverGeometry
The amount of space this sliver occupies. [...]
read / write, inherited
hashCode → int
The hash code for this object. [...]
read-only, inherited
isRepaintBoundary → bool
Whether this render object repaints separately from its parent. [...]
read-only, inherited
layer → OffsetLayer
The compositing layer that this render object uses to repaint. [...]
read-only, inherited
needsCompositing → bool
Whether we or one of our descendants has a compositing layer. [...]
read-only, inherited
owner → PipelineOwner
The owner for this node (null if unattached). [...]
read-only, inherited
paintBounds → Rect
An estimate of the bounds within which this render object will paint. Useful for debugging flags such as debugPaintLayerBordersEnabled. [...]
read-only, inherited
parent → AbstractNode
The parent of this node in the tree.
read-only, inherited
parentData ↔ ParentData
Data for use by the parent render object. [...]
read / write, inherited
runtimeType → Type
A representation of the runtime type of the object.
read-only, inherited
semanticBounds → Rect
The bounding box, in the local coordinate system, of this object, for accessibility purposes.
read-only, inherited
sizedByParent → bool
Whether the constraints are the only input to the sizing algorithm (in particular, child nodes have no impact). [...]
@protected, read-only, inherited

Methods

applyPaintTransform(covariant RenderObject child, Matrix4 transform) → void
Applies the transform that would be applied when painting the given child to the given matrix. [...]
override
childMainAxisPosition(covariant RenderObject child) → double
Returns the distance from the leading visible edge of the sliver to the side of the child closest to that edge, in the scroll axis direction. [...]
override
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node. [...]
override
describeSemanticsConfiguration(SemanticsConfiguration config) → void
Report the semantics of this node, for example for accessibility purposes. [...]
override
hitTestChildren(HitTestResult result, { double mainAxisPosition, double crossAxisPosition }) → bool
Override this method to check whether any children are located at the given position. [...]
override
layoutChild(double scrollOffset, double maxExtent, { bool overlapsContent: false }) → void
Lays out the child. [...]
@protected
markNeedsLayout() → void
Mark this render object's layout information as dirty, and either register this object with its PipelineOwner, or defer to the parent, depending on whether this object is a relayout boundary or not respectively. [...]
override
paint(PaintingContext context, Offset offset) → void
Paint this render object into the given context at the given offset. [...]
override
updateChild(double shrinkOffset, bool overlapsContent) → void
Update the child render object if necessary. [...]
@protected
adoptChild(covariant RenderObject child) → void
Called by subclasses when they decide a render object is a child. [...]
inherited
applyPaintTransformForBoxChild(RenderBox child, Matrix4 transform) → void
Utility function for applyPaintTransform for use when the children are RenderBox widgets. [...]
@protected, inherited
assembleSemanticsNode(SemanticsNode node, SemanticsConfiguration config, Iterable<SemanticsNode> children) → void
Assemble the SemanticsNode for this RenderObject. [...]
inherited
attach(covariant PipelineOwner owner) → void
Mark this node as attached to the given owner. [...]
inherited
calculateCacheOffset(SliverConstraints constraints, { double from, double to }) → double
Computes the portion of the region from from to to that is within the cache extent of the viewport, assuming that only the region from the SliverConstraints.cacheOrigin that is SliverConstraints.remainingCacheExtent high is visible, and that the relationship between scroll offsets and paint offsets is linear. [...]
inherited
calculatePaintOffset(SliverConstraints constraints, { double from, double to }) → double
Computes the portion of the region from from to to that is visible, assuming that only the region from the SliverConstraints.scrollOffset that is SliverConstraints.remainingPaintExtent high is visible, and that the relationship between scroll offsets and paint offsets is linear. [...]
inherited
childCrossAxisPosition(covariant RenderObject child) → double
Returns the distance along the cross axis from the zero of the cross axis in this sliver's paint coordinate space to the nearest side of the given child. [...]
@protected, inherited
childScrollOffset(covariant RenderObject child) → double
Returns the scroll offset for the leading edge of the given child. [...]
inherited
clearSemantics() → void
Removes all semantics from this render object and its descendants. [...]
@mustCallSuper, inherited
debugAssertDoesMeetConstraints() → void
Verify that the object's constraints are being met. Override this function in a subclass to verify that your state matches the constraints object. This function is only called in checked mode and only when needsLayout is false. If the constraints are not met, it should assert or throw an exception.
inherited
debugDescribeChildren() → List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children. [...]
inherited
debugPaint(PaintingContext context, Offset offset) → void
Override this method to paint debugging information.
inherited
debugRegisterRepaintBoundaryPaint({bool includedParent: true, bool includedChild: false }) → void
Called, in checked mode, if isRepaintBoundary is true, when either the this render object or its parent attempt to paint. [...]
inherited
debugResetSize() → void
If a subclass has a "size" (the state controlled by parentUsesSize, whatever it is in the subclass, e.g. the actual size property of RenderBox), and the subclass verifies that in checked mode this "size" property isn't used when debugCanParentUseSize isn't set, then that subclass should override debugResetSize to reapply the current values of debugCanParentUseSize to that state.
inherited
debugValidateChild(RenderObject child) → bool
Checks whether the given render object has the correct runtimeType to be a child of this render object. [...]
inherited
describeApproximatePaintClip(covariant RenderObject child) → Rect
Returns a rect in this object's coordinate system that describes the approximate bounding box of the clip rect that would be applied to the given child during the paint phase, if any. [...]
inherited
describeSemanticsClip(covariant RenderObject child) → Rect
Returns a rect in this object's coordinate system that describes which SemanticsNodes produced by the child should be included in the semantics tree. SemanticsNodes from the child that are positioned outside of this rect will be dropped. Child SemanticsNodes that are positioned inside this rect, but outside of describeApproximatePaintClip will be included in the tree marked as hidden. Child SemanticsNodes that are inside of both rect will be included in the tree as regular nodes. [...]
inherited
detach() → void
Mark this node as detached. [...]
inherited
dropChild(covariant RenderObject child) → void
Called by subclasses when they decide a render object is no longer a child. [...]
inherited
getAbsoluteSizeRelativeToOrigin() → Size
This returns a Size with dimensions relative to the leading edge of the sliver, specifically the same offset that is given to the paint method. This means that the dimensions may be negative. [...]
@protected, inherited
getTransformTo(RenderObject ancestor) → Matrix4
Applies the paint transform up the tree to ancestor. [...]
inherited
handleEvent(PointerEvent event, covariant SliverHitTestEntry entry) → void
Override this method to handle pointer events that hit this render object.
inherited
hitTest(HitTestResult result, { double mainAxisPosition, double crossAxisPosition }) → bool
Determines the set of render objects located at the given position. [...]
inherited
hitTestBoxChild(HitTestResult result, RenderBox child, { double mainAxisPosition, double crossAxisPosition }) → bool
Utility function for hitTestChildren for use when the children are RenderBox widgets. [...]
@protected, inherited
hitTestSelf({double mainAxisPosition, double crossAxisPosition }) → bool
Override this method if this render object can be hit even if its children were not hit. [...]
@protected, inherited
invokeLayoutCallback<T extends Constraints>(LayoutCallback<T> callback) → void
Allows mutations to be made to this object's child list (and any descendants) as well as to any other dirty nodes in the render tree owned by the same PipelineOwner as this object. The callback argument is invoked synchronously, and the mutations are allowed only during that callback's execution. [...]
@protected, inherited
layout(Constraints constraints, { bool parentUsesSize: false }) → void
Compute the layout for this render object. [...]
inherited
markNeedsCompositingBitsUpdate() → void
Mark the compositing state for this render object as dirty. [...]
inherited
markNeedsLayoutForSizedByParentChange() → void
Mark this render object's layout information as dirty (like markNeedsLayout), and additionally also handle any necessary work to handle the case where sizedByParent has changed value. [...]
inherited
markNeedsPaint() → void
Mark this render object as having changed its visual appearance. [...]
inherited
markNeedsSemanticsUpdate() → void
Mark this node as needing an update to its semantics description. [...]
inherited
markParentNeedsLayout() → void
Mark this render object's layout information as dirty, and then defer to the parent. [...]
@protected, inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
inherited
performLayout() → void
Do the work of computing the layout for this render object. [...]
@protected, inherited
performResize() → void
Updates the render objects size using only the constraints. [...]
inherited
reassemble() → void
Cause the entire subtree rooted at the given RenderObject to be marked dirty for layout, paint, etc, so that the effects of a hot reload can be seen, or so that the effect of changing a global debug flag (such as debugPaintSizeEnabled) can be applied. [...]
inherited
redepthChild(AbstractNode child) → void
Adjust the depth of the given child to be greater than this node's own depth. [...]
@protected, inherited
redepthChildren() → void
Adjust the depth of this node's children, if any. [...]
inherited
replaceRootLayer(OffsetLayer rootLayer) → void
Replace the layer. This is only valid for the root of a render object subtree (whatever object scheduleInitialPaint was called on). [...]
inherited
rotate({int oldAngle, int newAngle, Duration time }) → void
Rotate this render object (not yet implemented).
inherited
scheduleInitialLayout() → void
Bootstrap the rendering pipeline by scheduling the very first layout. [...]
inherited
scheduleInitialPaint(ContainerLayer rootLayer) → void
Bootstrap the rendering pipeline by scheduling the very first paint. [...]
inherited
scheduleInitialSemantics() → void
Bootstrap the semantics reporting mechanism by marking this node as needing a semantics update. [...]
inherited
sendSemanticsEvent(SemanticsEvent semanticsEvent) → void
Sends a SemanticsEvent associated with this render object's SemanticsNode. [...]
inherited
setupParentData(covariant RenderObject child) → void
Override to setup parent data correctly for your children. [...]
inherited
showOnScreen({RenderObject descendant, Rect rect, Duration duration: Duration.zero, Curve curve: Curves.ease }) → void
Attempt to make (a portion of) this or a descendant RenderObject visible on screen. [...]
inherited
toDiagnosticsNode({String name, DiagnosticsTreeStyle style }) → DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by toStringDeep. [...]
inherited
toString({DiagnosticLevel minLevel }) → String
Returns a string representation of this object.
inherited
toStringDeep({String prefixLineOne: '', String prefixOtherLines: '', DiagnosticLevel minLevel: DiagnosticLevel.debug }) → String
Returns a description of the tree rooted at this node. If the prefix argument is provided, then every line in the output will be prefixed by that string.
inherited
toStringShallow({String joiner: '; ', DiagnosticLevel minLevel: DiagnosticLevel.debug }) → String
Returns a one-line detailed description of the render object. This description is often somewhat long. [...]
inherited
toStringShort() → String
Returns a human understandable name.
inherited
visitChildren(RenderObjectVisitor visitor) → void
Calls visitor for each immediate child of this render object. [...]
inherited
visitChildrenForSemantics(RenderObjectVisitor visitor) → void
Called when collecting the semantics of this node. [...]
inherited

Operators

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