A widget that provides a canvas on which to draw during the paint phase.

When asked to paint,CustomPaint first asks itspainter to paint on thecurrent canvas, then it paints its child, and then, after painting itschild, it asks itsforegroundPainter to paint. The coordinate system of thecanvas matches the coordinate system of theCustomPaint object. Thepainters are expected to paint within a rectangle starting at the origin andencompassing a region of the given size. (If the painters paint outsidethose bounds, there might be insufficient memory allocated to rasterize thepainting commands and the resulting behavior is undefined.) To enforcepainting within those bounds, consider wrapping thisCustomPaint with aClipRect widget.

Painters are implemented by subclassingCustomPainter.

Because custom paint calls its painters during paint, you cannot callsetState ormarkNeedsLayout during the callback (the layout for thisframe has already happened).

Custom painters normally size themselves to theirchild. If they do nothave a child, they attempt to size themselves to the specifiedsize, whichdefaults toSize.zero. The parentmay enforce constraints on thissize.

TheisComplex andwillChange properties are hints to the compositor'sraster cache.

CustomPaint(  painter: Sky(),  child: const Center(    child: Text(      'Once upon a time...',      style: TextStyle(        fontSize: 40.0,        fontWeight: FontWeight.w900,        color: Color(0xFFFFFFFF),      ),    ),  ),)

See also:

• CustomPainter, the class to extend when creating custom painters.
• Canvas, the class that a custom painter uses to paint.

Inheritance

• Object
• DiagnosticableTree
• Widget
• RenderObjectWidget
• SingleChildRenderObjectWidget
• CustomPaint

Constructors

CustomPaint({Key?key,CustomPainter?painter,CustomPainter?foregroundPainter,Sizesize =Size.zero,boolisComplex =false,boolwillChange =false,Widget?child})

Creates a widget that delegates its painting.

const

Properties

child→Widget?

The widget below this widget in the tree.

finalinherited

foregroundPainter→CustomPainter?

The painter that paints after the children.

final

hashCode→int

The hash code for this object.

no setterinherited

isComplex→bool

Whether the painting is complex enough to benefit from caching.

final

key→Key?

Controls how one widget replaces another widget in the tree.

finalinherited

painter→CustomPainter?

The painter that paints before the children.

final

runtimeType→Type

A representation of the runtime type of the object.

no setterinherited

size→Size

The size that thisCustomPaint should aim for, given the layoutconstraints, if there is no child.

final

willChange→bool

Whether the raster cache should be told that this painting is likelyto change in the next frame.

final

Methods

createElement()→SingleChildRenderObjectElement

RenderObjectWidgets always inflate to aRenderObjectElement subclass.

inherited

createRenderObject(BuildContextcontext)→RenderCustomPaint

Creates an instance of theRenderObject class that thisRenderObjectWidget represents, using the configuration described by thisRenderObjectWidget.

override

debugDescribeChildren()→List<DiagnosticsNode>

Returns a list ofDiagnosticsNode objects describing this node'schildren.

inherited

debugFillProperties(DiagnosticPropertiesBuilderproperties)→ void

Add additional properties associated with the node.

inherited

didUnmountRenderObject(covariantRenderCustomPaintrenderObject)→ void

This method is called when a RenderObject that was previouslyassociated with this widget is removed from the render tree.The providedRenderObject will be of the same type as the one created bythis widget'screateRenderObject method.

override

noSuchMethod(Invocationinvocation)→ dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toDiagnosticsNode({String?name,DiagnosticsTreeStyle?style})→DiagnosticsNode

Returns a debug representation of the object that is used by debuggingtools and byDiagnosticsNode.toStringDeep.

inherited

toString({DiagnosticLevelminLevel =DiagnosticLevel.info})→String

A string representation of this object.

inherited

toStringDeep({StringprefixLineOne ='',String?prefixOtherLines,DiagnosticLevelminLevel =DiagnosticLevel.debug,intwrapWidth =65})→String

Returns a string representation of this node and its descendants.

inherited

toStringShallow({Stringjoiner =', ',DiagnosticLevelminLevel =DiagnosticLevel.debug})→String

Returns a one-line detailed description of the object.

inherited

toStringShort()→String

A short, textual description of this widget.

inherited

updateRenderObject(BuildContextcontext,covariantRenderCustomPaintrenderObject)→ void

Copies the configuration described by thisRenderObjectWidget to thegivenRenderObject, which will be of the same type as returned by thisobject'screateRenderObject.

override

Operators

operator ==(Objectother)→bool

The equality operator.

inherited