ConstraintsTransformBox class Null safety
A container widget that applies an arbitrary transform to its constraints, and sizes its child using the resulting BoxConstraints, treating any overflow as error.
This container sizes its child using a BoxConstraints created by applying constraintsTransform to its own constraints. This container will then attempt to adopt the same size, within the limits of its own constraints. If it ends up with a different size, it will align the child based on alignment. If the container cannot expand enough to accommodate the entire child, the child will be clipped if clipBehavior is not Clip.none.
In debug mode, if the child overflows the container, a warning will be printed on the console, and black and yellow striped areas will appear where the overflow occurs.
When child is null, this widget becomes as small as possible and never overflows
This widget can be used to ensure some of child's natural dimensions are honored, and get an early warning otherwise during development. For instance, if child requires a minimum height to fully display its content, constraintsTransform can be set to maxHeightUnconstrained, so that if the parent RenderObject fails to provide enough vertical space, a warning will be displayed in debug mode, while still allowing child to grow vertically:
Container(
constraints: const BoxConstraints(minHeight: 40, maxHeight: 100),
alignment: Alignment.center,
child: const ConstraintsTransformBox(
constraintsTransform: ConstraintsTransformBox.maxHeightUnconstrained,
child: Card(child: Text('Hello World!')),
)
)
See also:
- ConstrainedBox, which renders a box which imposes constraints on its child.
- OverflowBox, a widget that imposes additional constraints on its child, and allows the child to overflow itself.
- UnconstrainedBox which allows its children to render themselves unconstrained, expands to fit them, and considers overflow to be an error.
- Inheritance
-
- Object
- DiagnosticableTree
- Widget
- RenderObjectWidget
- SingleChildRenderObjectWidget
- ConstraintsTransformBox
Constructors
- ConstraintsTransformBox({Key? key, Widget? child, TextDirection? textDirection, AlignmentGeometry alignment = Alignment.center, required BoxConstraintsTransform constraintsTransform, Clip clipBehavior = Clip.none, String debugTransformType = ''})
-
Creates a widget that uses a function to transform the constraints it
passes to its child. If the child overflows the parent's constraints, a
warning will be given in debug mode.
const
Properties
- alignment → AlignmentGeometry
-
The alignment to use when laying out the child, if it has a different size
than this widget.
final
- child → Widget?
-
The widget below this widget in the tree.
finalinherited
- clipBehavior → Clip
-
The content will be clipped (or not) according to this option.
final
- constraintsTransform → BoxConstraintsTransform
-
The function used to transform the incoming BoxConstraints, to size
child.
final
- hashCode → int
- The hash code for this object.
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
- runtimeType → Type
-
A representation of the runtime type of the object.
read-onlyinherited
- textDirection → TextDirection?
-
The text direction to use when interpreting the alignment if it is an
AlignmentDirectional.
final
Methods
-
createElement(
) → SingleChildRenderObjectElement -
RenderObjectWidgets always inflate to a RenderObjectElement subclass.
inherited
-
createRenderObject(
BuildContext context) → RenderConstraintsTransformBox -
Creates an instance of the RenderObject class that this
RenderObjectWidget represents, using the configuration described by this
RenderObjectWidget.
override
-
debugDescribeChildren(
) → List< DiagnosticsNode> -
Returns a list of
DiagnosticsNode
objects describing this node's children.protected">@protectedinherited -
debugFillProperties(
DiagnosticPropertiesBuilder properties) → void -
Add additional properties associated with the node.
override
-
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.
protected">@protectedinherited
-
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a non-existent method or property is accessed.
inherited
-
toDiagnosticsNode(
{String? name, DiagnosticsTreeStyle? style}) → DiagnosticsNode -
Returns a debug representation of the object that is used by debugging
tools and by DiagnosticsNode.toStringDeep.
inherited
-
toString(
{DiagnosticLevel minLevel = DiagnosticLevel.info}) → String -
A string representation of this object.
inherited
-
toStringDeep(
{String prefixLineOne = '', String? prefixOtherLines, DiagnosticLevel minLevel = DiagnosticLevel.debug}) → String -
Returns a string representation of this node and its descendants.
inherited
-
toStringShallow(
{String joiner = ', ', DiagnosticLevel minLevel = DiagnosticLevel.debug}) → String -
Returns a one-line detailed description of the object.
inherited
-
toStringShort(
) → String -
A short, textual description of this widget.
inherited
-
updateRenderObject(
BuildContext context, covariant RenderConstraintsTransformBox 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.
override
Operators
-
operator ==(
Object other) → bool -
The equality operator.
nonVirtual">@nonVirtualinherited
Static Methods
-
heightUnconstrained(
BoxConstraints constraints) → BoxConstraints - A BoxConstraintsTransform that removes the height constraints from the input.
-
maxHeightUnconstrained(
BoxConstraints constraints) → BoxConstraints -
A BoxConstraintsTransform that removes the
maxHeight
constraint from the input. -
maxUnconstrained(
BoxConstraints constraints) → BoxConstraints -
A BoxConstraintsTransform that removes both the
maxWidth
and themaxHeight
constraints from the input. -
maxWidthUnconstrained(
BoxConstraints constraints) → BoxConstraints -
A BoxConstraintsTransform that removes the
maxWidth
constraint from the input. -
unconstrained(
BoxConstraints constraints) → BoxConstraints -
A BoxConstraintsTransform that always returns a BoxConstraints that
imposes no constraints on either dimension (i.e.
const BoxConstraints()
). -
unmodified(
BoxConstraints constraints) → BoxConstraints - A BoxConstraintsTransform that always returns its argument as-is (i.e., it is an identity function).
-
widthUnconstrained(
BoxConstraints constraints) → BoxConstraints - A BoxConstraintsTransform that removes the width constraints from the input.