SizedBox class Null safety
A box with a specified size.
If given a child, this widget forces it to have a specific width and/or height. These values will be ignored if this widget's parent does not permit them. For example, this happens if the parent is the screen (forces the child to be the same size as the parent), or another SizedBox (forces its child to have a specific width and/or height). This can be remedied by wrapping the child SizedBox in a widget that does permit it to be any size up to the size of the parent, such as Center or Align.
If either the width or height is null, this widget will try to size itself to match the child's size in that dimension. If the child's size depends on the size of its parent, the height and width must be provided.
If not given a child, SizedBox will try to size itself as close to the specified height and width as possible given the parent's constraints. If height or width is null or unspecified, it will be treated as zero.
The SizedBox.expand constructor can be used to make a SizedBox that sizes itself to fit the parent. It is equivalent to setting width and height to double.infinity.
See also:
- ConstrainedBox, a more generic version of this class that takes arbitrary BoxConstraints instead of an explicit width and height.
- UnconstrainedBox, a container that tries to let its child draw without constraints.
- FractionallySizedBox, a widget that sizes its child to a fraction of the total available space.
- AspectRatio, a widget that attempts to fit within the parent's constraints while also sizing its child to match a given aspect ratio.
- FittedBox, which sizes and positions its child widget to fit the parent according to a given BoxFit discipline.
- The catalog of layout widgets.
- Understanding constraints, an in-depth article about layout in Flutter.
- Inheritance
Constructors
- SizedBox({Key? key, double? width, double? height, Widget? child})
-
Creates a fixed size box. The width and height parameters can be null
to indicate that the size of the box should not be constrained in
the corresponding dimension.
const
- SizedBox.expand({Key? key, Widget? child})
-
Creates a box that will become as large as its parent allows.
const
- SizedBox.fromSize({Key? key, Widget? child, Size? size})
- Creates a box with the specified size.
- SizedBox.shrink({Key? key, Widget? child})
-
Creates a box that will become as small as its parent allows.
const
- SizedBox.square({Key? key, Widget? child, double? dimension})
-
Creates a box whose width and height are equal.
const
Properties
- child → Widget?
-
The widget below this widget in the tree.
finalinherited
- hashCode → int
- The hash code for this object.
- height → double?
-
If non-null, requires the child to have exactly this height.
final
- 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
- width → double?
-
If non-null, requires the child to have exactly this width.
final
Methods
-
createElement(
) → SingleChildRenderObjectElement -
RenderObjectWidgets always inflate to a RenderObjectElement subclass.
inherited
-
createRenderObject(
BuildContext context) → RenderConstrainedBox -
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.
override
-
updateRenderObject(
BuildContext context, covariant RenderConstrainedBox 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