Positioned class

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, Rect rect, @required Widget child })
Creates a Positioned object with the values from the given Rect. [...]
Positioned.fromRelativeRect({Key key, 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
height → double
The child's height. [...]
final
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
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
child → Widget
The widget below this widget in the tree. [...]
final, inherited
hashCode → int
The hash code for this object. [...]
read-only, inherited
key → Key
Controls how one widget replaces another widget in the tree. [...]
final, inherited
runtimeType → Type
A representation of the runtime type of the object.
read-only, inherited

Methods

applyParentData(RenderObject renderObject) → void
Write the data from this widget into the given render object's parent data. [...]
override
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node. [...]
override
createElement() → ParentDataElement<Stack>
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
debugDescribeInvalidAncestorChain({String description, String ownershipChain, bool foundValidAncestor, Iterable<Widget> badAncestors }) → String
Subclasses should override this to describe the requirements for using the ParentDataWidget subclass. It is called when debugIsValidAncestor() returned false for an ancestor, or when there are extraneous ParentDataWidgets in the ancestor chain.
inherited
debugIsValidAncestor(RenderObjectWidget ancestor) → bool
Subclasses should override this method to return true if the given ancestor is a RenderObjectWidget that wraps a RenderObject that can handle the kind of ParentData widget that the ParentDataWidget subclass handles. [...]
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 toStringDeep. [...]
inherited
toString({DiagnosticLevel minLevel: DiagnosticLevel.debug }) → 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 ==(dynamic other) → bool
The equality operator. [...]
inherited