Draggable<T> 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.

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.

See also:

Inheritance
Implemented by

Constructors

Draggable({Key key, @required Widget child, @required Widget feedback, T data, Axis axis, Widget childWhenDragging, Offset feedbackOffset: Offset.zero, DragAnchor dragAnchor: DragAnchor.child, Axis affinity, int maxSimultaneousDrags, VoidCallback onDragStarted, DraggableCanceledCallback onDraggableCanceled, VoidCallback onDragCompleted })
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.
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
maxSimultaneousDrags int
How many simultaneous drags to support. [...]
final
onDragCompleted VoidCallback
Called when the draggable is dropped and accepted by a DragTarget. [...]
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
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

createRecognizer(GestureMultiDragStartCallback onStart) MultiDragGestureRecognizer<MultiDragPointerState>
Creates a gesture recognizer that recognizes the start of the drag. [...]
@protected
createState() → _DraggableState<T>
Creates the mutable state for this widget at a given location in the tree. [...]
createElement() StatefulElement
Creates a StatefulElement to manage this widget's location in the tree. [...]
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