SelectionPainter class abstract

SelectionPainter

To implement a custom selection painter, either subclass or implement this interface to define your custom paint delegate. SelectionPainter subclasses must implement the paint and shouldRepaint methods, and may optionally also implement the hitTest method.

The paint method is called whenever the custom object needs to be repainted.

The shouldRepaint method is called when a new instance of the class is provided, to check if the new instance actually represents different information.

The most efficient way to trigger a repaint is to either:

  • Extend this class and supply a repaint argument to the constructor of the SelectionPainter, where that object notifies its listeners when it is time to repaint.
  • Extend Listenable (e.g. via ChangeNotifier) and implement SelectionPainter, so that the object itself provides the notifications directly.

In either case, the Selectable widget or RenderSelectable render object will listen to the Listenable and repaint whenever the animation ticks, avoiding both the build and layout phases of the pipeline.

The hitTest method is called when the user interacts with the underlying render object, to determine if the user hit the object or missed it.

Inheritance
Implementers

Constructors

SelectionPainter({Listenable? repaint})
Creates a custom selection painter.
const

Properties

hashCode → int
The hash code for this object.
no setterinherited
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited

Methods

addListener(VoidCallback listener) → void
Register a closure to be notified when it is time to repaint.
override
hitTest(Offset position) → bool?
Called whenever a hit test is being performed on an object that is using this custom paint delegate.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
paint(Canvas canvas, Size size, Selection selection) → void
Called whenever the object needs to paint. The Canvas has its coordinate space configured such that the origin is at the top left of the box. The area of the box is the size of the size argument.
removeListener(VoidCallback listener) → void
Remove a previously registered closure from the list of closures that the object notifies when it is time to repaint.
override
shouldRepaint(covariant SelectionPainter oldDelegate) → bool
Called whenever a new instance of the custom painter delegate class is provided to the RenderSelectable object, or any time that a new Selectable object is created with a new instance of the custom painter delegate class (which amounts to the same thing, because the latter is implemented in terms of the former).
toString() → String
A string representation of this object.
override

Operators

operator ==(Object other) → bool
The equality operator.
inherited