CustomPaint class
A widget that provides a canvas on which to draw during the paint phase.
When asked to paint, CustomPaint first asks its painter to paint on the current canvas, then it paints its child, and then, after painting its child, it asks its foregroundPainter to paint. The coordinate system of the canvas matches the coordinate system of the CustomPaint object. The painters are expected to paint within a rectangle starting at the origin and encompassing a region of the given size. (If the painters paint outside those bounds, there might be insufficient memory allocated to rasterize the painting commands and the resulting behavior is undefined.)
Painters are implemented by subclassing CustomPainter.
Because custom paint calls its painters during paint, you cannot call
setState or markNeedsLayout during the callback (the layout for this
frame has already happened).
Custom painters normally size themselves to their child. If they do not have a child, they attempt to size themselves to the size, which defaults to Size.zero. size must not be null.
isComplex and willChange are hints to the compositor's raster cache and must not be null.
CustomPaint(
painter: Sky(),
child: Center(
child: Text(
'Once upon a time...',
style: const 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
Constructors
- CustomPaint({Key key, CustomPainter painter, CustomPainter foregroundPainter, Size size: Size.zero, bool isComplex: false, bool willChange: false, Widget child })
-
Creates a widget that delegates its painting.
const
Properties
- foregroundPainter → CustomPainter
-
The painter that paints after the children.
final
- isComplex → bool
-
Whether the painting is complex enough to benefit from caching. [...]
final
- painter → CustomPainter
-
The painter that paints before the children.
final
- size → Size
-
The size that this CustomPaint should aim for, given the layout
constraints, if there is no child. [...]
final
- willChange → bool
-
Whether the raster cache should be told that this painting is likely
to change in the next frame.
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
-
createRenderObject(
BuildContext context) → RenderCustomPaint -
Creates an instance of the RenderObject class that this
RenderObjectWidget represents, using the configuration described by this
RenderObjectWidget. [...]
override
-
didUnmountRenderObject(
covariant RenderCustomPaint 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.
override
-
updateRenderObject(
BuildContext context, covariant RenderCustomPaint 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. [...]
override
-
createElement(
) → SingleChildRenderObjectElement -
RenderObjectWidgets always inflate to a RenderObjectElement subclass.
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. [...]
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