Draggable<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.
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
-
- Object
- DiagnosticableTree
- Widget
- StatefulWidget
- Draggable
- Implementers
Constructors
- Draggable({Key? key, required Widget child, required Widget feedback, T? data, Axis? axis, Widget? childWhenDragging, Offset feedbackOffset = Offset.zero, DragAnchorStrategy dragAnchorStrategy = childDragAnchorStrategy, 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, AllowedButtonsFilter? allowedButtonsFilter})
-
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
- allowedButtonsFilter → AllowedButtonsFilter?
-
Called when interaction starts. This limits the dragging behavior
for custom clicks (such as scroll click). Its parameter comes
from PointerEvent.buttons.
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
- 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
- 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
-
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.
-
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.
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