A widget that uses the stack layout algorithm for its children.

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). The positioned children are then placed relative to the stack according to their top, right, bottom, and left properties.

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:

  • Align, which sizes itself based on its child's size and positions the child according to a FractionalOffset value.
  • CustomSingleChildLayout, which uses a delegate to control the layout of a single child.
  • CustomMultiChildLayout, which uses a delegate to position multiple children.
  • Flow, which provides paint-time control of its children using transform matrices.
Inheritance

Constructors

Stack({Key key, FractionalOffset alignment: FractionalOffset.topLeft, Overflow overflow: Overflow.clip, List<Widget> children: const [] })

Creates a stack layout widget.

Properties

alignment FractionalOffset

How to align the non-positioned children in the stack.

read-only
overflow Overflow

Whether overflowing children should be clipped. See Overflow.

read-only
children List<Widget>

The widgets below this widget in the tree.

read-only, inherited
hashCode int

Get a hash code for this object.

read-only, inherited
key Key

Controls how one widget replaces another widget in the tree.

read-only, inherited
runtimeType Type

A representation of the runtime type of the object.

read-only, inherited

Operators

operator ==(other) bool

The equality operator.

inherited

Methods

createRenderObject(BuildContext context) RenderStack

Creates an instance of the RenderObject class that this RenderObjectWidget represents, using the configuration described by this RenderObjectWidget.

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.

inherited
debugFillDescription(List<String> description) → void

Add additional information to the given description for use by toString.

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.

inherited
noSuchMethod(Invocation invocation) → dynamic

Invoked when a non-existent method or property is accessed.

inherited
toString() String

Returns a string representation of this object.

inherited
toStringShort() String

A short, textual description of this widget.

inherited