Draggable<T extends Object> class Null safety

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.

link
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.
To create a local project with this code sample, run:
flutter create --sample=widgets.Draggable.1 mysample

See also:

Inheritance
Implementers

Constructors

Draggable({Key? key, required Widget child, 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.') DragAnchor 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
child → Widget
The widget below this widget in the tree.
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 → DragAnchor
Where this widget should be anchored during a drag.
Deprecated('Use dragAnchorStrategy instead. ' 'This feature was deprecated after v2.1.0-10.0.pre.')">@Deprecated('Use dragAnchorStrategy instead. ' 'This feature was deprecated after v2.1.0-10.0.pre.')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.
nonVirtual">@nonVirtualread-onlyinherited
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
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.
read-onlyinherited

Methods

createElement() → StatefulElement
Creates a StatefulElement to manage this widget's location in the tree.
inherited
createRecognizer(GestureMultiDragStartCallback onStart) → MultiDragGestureRecognizer
Creates a gesture recognizer that recognizes the start of the drag.
protected">@protected
createState() → State<Draggable<T>>
Creates the mutable state for this widget at a given location in the tree.
override
debugDescribeChildren() → List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children.
protected">@protectedinherited
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 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.
nonVirtual">@nonVirtualinherited