AspectRatio class Null safety

A widget that attempts to size the child to a specific aspect ratio.

The widget first tries the largest width permitted by the layout constraints. The height of the widget is determined by applying the given aspect ratio to the width, expressed as a ratio of width to height.

For example, a 16:9 width:height aspect ratio would have a value of 16.0/9.0. If the maximum width is infinite, the initial width is determined by applying the aspect ratio to the maximum height.

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This examples shows how AspectRatio sets width when its parent's width constraint is infinite. Since its parent's allowed height is a fixed value, the actual width is determined via the given AspectRatio.

Since the height is fixed at 100.0 in this example and the aspect ratio is set to 16 / 9, the width should then be 100.0 / 9 * 16.

To create a local project with this code sample, run:
flutter create --sample=widgets.AspectRatio.1 mysample

Now consider a second example, this time with an aspect ratio of 2.0 and layout constraints that require the width to be between 0.0 and 100.0 and the height to be between 0.0 and 100.0. We'll select a width of 100.0 (the biggest allowed) and a height of 50.0 (to match the aspect ratio).

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To create a local project with this code sample, run:
flutter create --sample=widgets.AspectRatio.2 mysample

In that same situation, if the aspect ratio is 0.5, we'll also select a width of 100.0 (still the biggest allowed) and we'll attempt to use a height of 200.0. Unfortunately, that violates the constraints because the child can be at most 100.0 pixels tall. The widget will then take that value and apply the aspect ratio again to obtain a width of 50.0. That width is permitted by the constraints and the child receives a width of 50.0 and a height of 100.0. If the width were not permitted, the widget would continue iterating through the constraints. If the widget does not find a feasible size after consulting each constraint, the widget will eventually select a size for the child that meets the layout constraints but fails to meet the aspect ratio constraints.

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To create a local project with this code sample, run:
flutter create --sample=widgets.AspectRatio.3 mysample

See also:

Inheritance

Constructors

AspectRatio({Key? key, required double aspectRatio, Widget? child})
Creates a widget with a specific aspect ratio.
const

Properties

aspectRatio → double
The aspect ratio to attempt to use.
final
child → Widget?
The widget below this widget in the tree.
finalinherited
hashCode → int
The hash code for this object.
nonVirtual">@nonVirtualread-onlyinherited
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

Methods

createElement() → SingleChildRenderObjectElement
RenderObjectWidgets always inflate to a RenderObjectElement subclass.
inherited
createRenderObject(BuildContext context) → RenderAspectRatio
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 RenderAspectRatio 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