DragGestureRecognizer class Null safety

Recognizes movement.

In contrast to MultiDragGestureRecognizer, DragGestureRecognizer recognizes a single gesture sequence for all the pointers it watches, which means that the recognizer has at most one drag sequence active at any given time regardless of how many pointers are in contact with the screen.

DragGestureRecognizer is not intended to be used directly. Instead, consider using one of its subclasses to recognize specific types for drag gestures.

DragGestureRecognizer competes on pointer events of kPrimaryButton only when it has at least one non-null callback. If it has no callbacks, it is a no-op.

See also:

Inheritance
Implementers

Constructors

DragGestureRecognizer({Object? debugOwner, PointerDeviceKind? kind, DragStartBehavior dragStartBehavior, GestureVelocityTrackerBuilder velocityTrackerBuilder})
Initialize the object. [...]

Properties

debugDescription → String
Returns a very short pretty description of the gesture that the recognizer looks for, like 'tap' or 'horizontal drag'.
read-only, inherited
debugOwner → Object?
The recognizer's owner. [...]
final, inherited
dragStartBehavior ↔ DragStartBehavior
Configure the behavior of offsets sent to onStart. [...]
read / write
hashCode → int
The hash code for this object. [...]
read-only, inherited
maxFlingVelocity ↔ double?
Fling velocity magnitudes will be clamped to this value. [...]
read / write
minFlingDistance ↔ double?
The minimum distance an input pointer drag must have moved to to be considered a fling gesture. [...]
read / write
minFlingVelocity ↔ double?
The minimum velocity for an input pointer drag to be considered fling. [...]
read / write
onCancel ↔ GestureDragCancelCallback?
The pointer that previously triggered onDown did not complete. [...]
read / write
onDown ↔ GestureDragDownCallback?
A pointer has contacted the screen with a primary button and might begin to move. [...]
read / write
onEnd ↔ GestureDragEndCallback?
A pointer that was previously in contact with the screen with a primary button and moving is no longer in contact with the screen and was moving at a specific velocity when it stopped contacting the screen. [...]
read / write
onStart ↔ GestureDragStartCallback?
A pointer has contacted the screen with a primary button and has begun to move. [...]
read / write
onUpdate ↔ GestureDragUpdateCallback?
A pointer that is in contact with the screen with a primary button and moving has moved again. [...]
read / write
runtimeType → Type
A representation of the runtime type of the object.
read-only, inherited
team ↔ GestureArenaTeam?
The team that this recognizer belongs to, if any. [...]
read / write, inherited
velocityTrackerBuilder ↔ GestureVelocityTrackerBuilder
Determines the type of velocity estimation method to use for a potential drag gesture, when a new pointer is added. [...]
read / write

Methods

acceptGesture(int pointer) → void
Called when this member wins the arena for the given pointer id.
override
addAllowedPointer(PointerEvent event) → void
Registers a new pointer that's been checked to be allowed by this gesture recognizer. [...]
override
addPointer(PointerDownEvent event) → void
Registers a new pointer that might be relevant to this gesture detector. [...]
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. [...]
override
didStopTrackingLastPointer(int pointer) → void
Called when the number of pointers this recognizer is tracking changes from one to zero. [...]
override
dispose() → void
Releases any resources used by the object. [...]
override
getKindForPointer(int pointer) → PointerDeviceKind
For a given pointer ID, returns the device kind associated with it. [...]
@protected, inherited
handleEvent(PointerEvent event) → void
Called when a pointer event is routed to this recognizer.
override
handleNonAllowedPointer(PointerDownEvent event) → void
Handles a pointer being added that's not allowed by this recognizer. [...]
inherited
invokeCallback<T>(String name, RecognizerCallback<T> callback, {String debugReport()?}) → T?
Invoke a callback provided by the application, catching and logging any exceptions. [...]
@protected, inherited
isFlingGesture(VelocityEstimate estimate, PointerDeviceKind kind) → bool
Determines if a gesture is a fling or not based on velocity. [...]
isPointerAllowed(PointerEvent event) → bool
Checks whether or not a pointer is allowed to be tracked by this recognizer.
override
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
inherited
rejectGesture(int pointer) → void
Called when this member loses the arena for the given pointer id.
override
resolve(GestureDisposition disposition) → void
Resolves this recognizer's participation in each gesture arena with the given disposition.
@mustCallSuper, @protected, inherited
resolvePointer(int pointer, GestureDisposition disposition) → void
Resolves this recognizer's participation in the given gesture arena with the given disposition.
@mustCallSuper, @protected, inherited
startTrackingPointer(int pointer, [Matrix4? transform]) → void
Causes events related to the given pointer ID to be routed to this recognizer. [...]
@protected, inherited
stopTrackingIfPointerNoLongerDown(PointerEvent event) → void
Stops tracking the pointer associated with the given event if the event is a PointerUpEvent or a PointerCancelEvent event.
@protected, inherited
stopTrackingPointer(int pointer) → void
Stops events related to the given pointer ID from being routed to this recognizer. [...]
@protected, 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 brief description of this object, usually just the runtimeType and the hashCode. [...]
inherited

Operators

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