Stack class

A widget that positions its children relative to the edges of its box.

This class is useful if you want to overlap several children in a simple way, for example having some text and an image, overlaid with a gradient and a button attached to the bottom.

Each child of a Stack widget is either positioned or non-positioned. Positioned children are those wrapped in a Positioned widget that has at least one non-null property. The stack sizes itself to contain all the non-positioned children, which are positioned according to alignment (which defaults to the top-left corner in left-to-right environments and the top-right corner in right-to-left environments). The positioned children are then placed relative to the stack according to their top, right, bottom, and left properties.

The stack paints its children in order with the first child being at the bottom. If you want to change the order in which the children paint, you can rebuild the stack with the children in the new order. If you reorder the children in this way, consider giving the children non-null keys. These keys will cause the framework to move the underlying objects for the children to their new locations rather than recreate them at their new location.

For more details about the stack layout algorithm, see RenderStack.

If you want to lay a number of children out in a particular pattern, or if you want to make a custom layout manager, you probably want to use CustomMultiChildLayout instead. In particular, when using a Stack you can't position children relative to their size or the stack's own size.

See also:

Implemented by


Stack({Key key, AlignmentGeometry alignment: AlignmentDirectional.topStart, TextDirection textDirection, StackFit fit: StackFit.loose, Overflow overflow: Overflow.clip, List<Widget> children: const [] })
Creates a stack layout widget. [...]


alignment AlignmentGeometry
How to align the non-positioned and partially-positioned children in the stack. [...]
fit StackFit
How to size the non-positioned children in the stack. [...]
overflow Overflow
Whether overflowing children should be clipped. See Overflow. [...]
textDirection TextDirection
The text direction with which to resolve alignment. [...]
children → List<Widget>
The widgets 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


createRenderObject(BuildContext context) RenderStack
Creates an instance of the RenderObject class that this RenderObjectWidget represents, using the configuration described by this RenderObjectWidget. [...]
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
updateRenderObject(BuildContext context, RenderStack 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. [...]
createElement() MultiChildRenderObjectElement
RenderObjectWidgets always inflate to a RenderObjectElement subclass.
debugDescribeChildren() → List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children. [...]
@protected, inherited
didUnmountRenderObject(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, inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
toDiagnosticsNode({String name, DiagnosticsTreeStyle style }) DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by toStringDeep. [...]
toString({DiagnosticLevel minLevel: DiagnosticLevel.debug }) → String
Returns a string representation of this object.
toStringDeep({String prefixLineOne: '', String prefixOtherLines, DiagnosticLevel minLevel: DiagnosticLevel.debug }) → String
Returns a string representation of this node and its descendants. [...]
toStringShallow({String joiner: ', ', DiagnosticLevel minLevel: DiagnosticLevel.debug }) → String
Returns a one-line detailed description of the object. [...]
toStringShort() → String
A short, textual description of this widget.


operator ==(dynamic other) → bool
The equality operator. [...]