DraggableModifier<T extends Object> class

A widget that can be dragged from to a DragTarget.

When a draggable widget recognizes the start of a drag gesture, it displays a feedback widget that tracks the user's finger across the screen. If the user lifts their finger while on top of a DragTarget, that target is given the opportunity to accept the data carried by the draggable.

The ignoringFeedbackPointer defaults to true, which means that the feedback widget ignores the pointer during hit testing. Similarly, ignoringFeedbackSemantics defaults to true, and the feedback also ignores semantics when building the semantics tree.

On multitouch devices, multiple drags can occur simultaneously because there can be multiple pointers in contact with the device at once. To limit the number of simultaneous drags, use the maxSimultaneousDrags property. The default is to allow an unlimited number of simultaneous drags.

This widget displays child when zero drags are under way. If childWhenDragging is non-null, this widget instead displays childWhenDragging when one or more drags are underway. Otherwise, this widget always displays child.

{@tool dartpad} The following example has a Draggable widget along with a DragTarget in a row demonstrating an incremented acceptedData integer value when you drag the element to the target.

** See code in examples/api/lib/widgets/drag_target/draggable.0.dart ** {@end-tool}

See also:

Inheritance
Available extensions

Constructors

DraggableModifier({Key? key, Widget? child, Key? modifierKey, required Widget feedback, T? data, Axis? axis, Widget? childWhenDragging, Offset feedbackOffset = Offset.zero, @Deprecated('Use dragAnchorStrategy instead. ' 'Replace "dragAnchor: DragAnchor.child" with "dragAnchorStrategy: childDragAnchorStrategy". ' 'Replace "dragAnchor: DragAnchor.pointer" with "dragAnchorStrategy: pointerDragAnchorStrategy". ' 'This feature was deprecated after v2.1.0-10.0.pre.') dynamic dragAnchor = DragAnchor.child, DragAnchorStrategy? dragAnchorStrategy, Axis? affinity, int? maxSimultaneousDrags, VoidCallback? onDragStarted, DragUpdateCallback? onDragUpdate, DraggableCanceledCallback? onDraggableCanceled, DragEndCallback? onDragEnd, VoidCallback? onDragCompleted, bool ignoringFeedbackSemantics = true, bool ignoringFeedbackPointer = true, bool rootOverlay = false, HitTestBehavior hitTestBehavior = HitTestBehavior.deferToChild})
Creates a widget that can be dragged to a DragTarget.
const

Properties

affinity → Axis?
Controls how this widget competes with other gestures to initiate a drag.
final
axis → Axis?
The Axis to restrict this draggable's movement, if specified.
final
childWhenDragging → Widget?
The widget to display instead of child when one or more drags are under way.
final
data → T?
The data that will be dropped by this draggable.
final
dragAnchor → dynamic
Where this widget should be anchored during a drag.
final
dragAnchorStrategy → DragAnchorStrategy?
A strategy that is used by this draggable to get the anchor offset when it is dragged.
final
feedback → Widget
The widget to show under the pointer when a drag is under way.
final
feedbackOffset → Offset
The feedbackOffset can be used to set the hit test target point for the purposes of finding a drag target. It is especially useful if the feedback is transformed compared to the child.
final
hashCode → int
The hash code for this object.
no setterinherited
hitTestBehavior → HitTestBehavior
How to behave during hit test.
final
ignoringFeedbackPointer → bool
Whether the feedback widget is ignored during hit testing.
final
ignoringFeedbackSemantics → bool
Whether the semantics of the feedback widget is ignored when building the semantics tree.
final
key → Key?
Controls how one widget replaces another widget in the tree.
finalinherited
maxSimultaneousDrags → int?
How many simultaneous drags to support.
final
modifierKey → Key?
The actual key of the widget, which Modifier wrapped
finalinherited
onDragCompleted → VoidCallback?
Called when the draggable is dropped and accepted by a DragTarget.
final
onDragEnd → DragEndCallback?
Called when the draggable is dropped.
final
onDraggableCanceled → DraggableCanceledCallback?
Called when the draggable is dropped without being accepted by a DragTarget.
final
onDragStarted → VoidCallback?
Called when the draggable starts being dragged.
final
onDragUpdate → DragUpdateCallback?
Called when the draggable is dragged.
final
rootOverlay → bool
Whether the feedback widget will be put on the root Overlay.
final
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited

Methods

build(BuildContext context) → Widget
Describes the part of the user interface represented by this widget.
inherited
buildWithChild(BuildContext context, Widget? child) → Widget
A build method that receives an extra child parameter.
override
createElement() → SingleChildStatelessElement
Create a SingleChildStatelessElement
inherited
debugDescribeChildren() → List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children.
inherited
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node.
inherited
noSuchMethod(Invocation invocation) → 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 debugging tools and by DiagnosticsNode.toStringDeep.
inherited
toString({DiagnosticLevel minLevel = DiagnosticLevel.info}) → String
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 ==(Object other) → bool
The equality operator.
inherited