CompositedTransformFollower class

A widget that follows a CompositedTransformTarget.

When this widget is composited during the compositing phase (which comes after the paint phase, as described in WidgetsBinding.drawFrame), it applies a transformation that brings targetAnchor of the linked CompositedTransformTarget and followerAnchor of this widget together. The two anchor points will have the same global coordinates, unless offset is not, in which case followerAnchor will be offset by offset in the linked CompositedTransformTarget's coordinate space.

The LayerLink object used as the link must be the same object as that provided to the matching CompositedTransformTarget.

The CompositedTransformTarget must come earlier in the paint order than this CompositedTransformFollower.

Hit testing on descendants of this widget will only work if the target position is within the box that this widget's parent considers to be hittable. If the parent covers the screen, this is trivially achievable, so this widget is usually used as the root of an OverlayEntry in an app-wide Overlay (e.g. as created by the MaterialApp widget's Navigator).

See also:



CompositedTransformFollower({Key? key, required LayerLink link, bool showWhenUnlinked = true, Offset offset =, Alignment targetAnchor = Alignment.topLeft, Alignment followerAnchor = Alignment.topLeft, Widget? child})
Creates a composited transform target widget.


child Widget?
The widget below this widget in the tree.
followerAnchor Alignment
The anchor point on this widget that will line up with targetAnchor on the linked CompositedTransformTarget.
hashCode int
The hash code for this object.
no setterinherited
key Key?
Controls how one widget replaces another widget in the tree.
The link object that connects this CompositedTransformFollower with a CompositedTransformTarget.
offset Offset
The additional offset to apply to the targetAnchor of the linked CompositedTransformTarget to obtain this widget's followerAnchor position.
runtimeType Type
A representation of the runtime type of the object.
no setterinherited
showWhenUnlinked bool
Whether to show the widget's contents when there is no corresponding CompositedTransformTarget with the same link.
targetAnchor Alignment
The anchor point on the linked CompositedTransformTarget that followerAnchor will line up with.


createElement() SingleChildRenderObjectElement
RenderObjectWidgets always inflate to a RenderObjectElement subclass.
createRenderObject(BuildContext context) RenderFollowerLayer
Creates an instance of the RenderObject class that this RenderObjectWidget represents, using the configuration described by this RenderObjectWidget.
debugDescribeChildren() List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children.
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node.
didUnmountRenderObject(covariant RenderObject renderObject) → void
A render object previously associated with this widget has been removed from the tree. The given RenderObject will be of the same type as returned by this object's createRenderObject.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
toDiagnosticsNode({String? name, DiagnosticsTreeStyle? style}) DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by DiagnosticsNode.toStringDeep.
toString({DiagnosticLevel minLevel =}) String
A string representation of this object.
toStringDeep({String prefixLineOne = '', String? prefixOtherLines, DiagnosticLevel minLevel = DiagnosticLevel.debug}) String
Returns a string representation of this node and its descendants.
toStringShallow({String joiner = ', ', DiagnosticLevel minLevel = DiagnosticLevel.debug}) String
Returns a one-line detailed description of the object.
toStringShort() String
A short, textual description of this widget.
updateRenderObject(BuildContext context, covariant RenderFollowerLayer renderObject) → void
Copies the configuration described by this RenderObjectWidget to the given RenderObject, which will be of the same type as returned by this object's createRenderObject.


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