Positioned class Null safety

A widget that controls where a child of a Stack is positioned.

A Positioned widget must be a descendant of a Stack, and the path from the Positioned widget to its enclosing Stack must contain only StatelessWidgets or StatefulWidgets (not other kinds of widgets, like RenderObjectWidgets).

If a widget is wrapped in a Positioned, then it is a positioned widget in its Stack. If the top property is non-null, the top edge of this child will be positioned top layout units from the top of the stack widget. The right, bottom, and left properties work analogously.

If both the top and bottom properties are non-null, then the child will be forced to have exactly the height required to satisfy both constraints. Similarly, setting the right and left properties to non-null values will force the child to have a particular width. Alternatively the width and height properties can be used to give the dimensions, with one corresponding position property (e.g. top and height).

If all three values on a particular axis are null, then the Stack.alignment property is used to position the child.

If all six values are null, the child is a non-positioned child. The Stack uses only the non-positioned children to size itself.

See also:

Inheritance

Constructors

Positioned({Key? key, double? left, double? top, double? right, double? bottom, double? width, double? height, required Widget child})
Creates a widget that controls where a child of a Stack is positioned. [...]
const
Positioned.directional({Key? key, required TextDirection textDirection, double? start, double? top, double? end, double? bottom, double? width, double? height, required Widget child})
Creates a widget that controls where a child of a Stack is positioned. [...]
factory
Positioned.fill({Key? key, double? left: 0.0, double? top: 0.0, double? right: 0.0, double? bottom: 0.0, required Widget child})
Creates a Positioned object with left, top, right, and bottom set to 0.0 unless a value for them is passed.
const
Positioned.fromRect({Key? key, required Rect rect, required Widget child})
Creates a Positioned object with the values from the given Rect. [...]
Positioned.fromRelativeRect({Key? key, required RelativeRect rect, required Widget child})
Creates a Positioned object with the values from the given RelativeRect. [...]

Properties

bottom double?
The distance that the child's bottom edge is inset from the bottom of the stack. [...]
final
child Widget
The widget below this widget in the tree. [...]
final, inherited
debugTypicalAncestorWidgetClass Type
The RenderObjectWidget that is typically used to set up the ParentData that applyParentData will write to. [...]
read-only, override
hashCode int
The hash code for this object. [...]
@nonVirtual, read-only, inherited
height double?
The child's height. [...]
final
key Key?
Controls how one widget replaces another widget in the tree. [...]
final, inherited
left double?
The distance that the child's left edge is inset from the left of the stack. [...]
final
The distance that the child's right edge is inset from the right of the stack. [...]
final
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited
top double?
The distance that the child's top edge is inset from the top of the stack. [...]
final
width double?
The child's width. [...]
final

Methods

applyParentData(RenderObject renderObject) → void
Write the data from this widget into the given render object's parent data. [...]
override
createElement() ParentDataElement<StackParentData>
Inflates this configuration to a concrete instance. [...]
inherited
debugCanApplyOutOfTurn() bool
Whether the ParentDataElement.applyWidgetOutOfTurn method is allowed with this widget. [...]
@protected, inherited
debugDescribeChildren() List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children. [...]
@protected, inherited
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node. [...]
override
debugIsValidRenderObject(RenderObject renderObject) bool
Checks if this widget can apply its parent data to the provided renderObject. [...]
inherited
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
Returns 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

Operators

operator ==(Object other) bool
The equality operator. [...]
@nonVirtual, inherited