GestureBinding mixin Null safety

A binding for the gesture subsystem.

Lifecycle of pointer events and the gesture arena

PointerDownEvent

When a PointerDownEvent is received by the GestureBinding (from dart:ui.PlatformDispatcher.onPointerDataPacket, as interpreted by the PointerEventConverter), a hitTest is performed to determine which HitTestTarget nodes are affected. (Other bindings are expected to implement hitTest to defer to HitTestable objects. For example, the rendering layer defers to the RenderView and the rest of the render object hierarchy.)

The affected nodes then are given the event to handle (dispatchEvent calls HitTestTarget.handleEvent for each affected node). If any have relevant GestureRecognizers, they provide the event to them using GestureRecognizer.addPointer. This typically causes the recognizer to register with the PointerRouter to receive notifications regarding the pointer in question.

Once the hit test and dispatching logic is complete, the event is then passed to the aforementioned PointerRouter, which passes it to any objects that have registered interest in that event.

Finally, the gestureArena is closed for the given pointer (GestureArenaManager.close), which begins the process of selecting a gesture to win that pointer.

Other events

A pointer that is PointerEvent.down may send further events, such as PointerMoveEvent, PointerUpEvent, or PointerCancelEvent. These are sent to the same HitTestTarget nodes as were found when the PointerDownEvent was received (even if they have since been disposed; it is the responsibility of those objects to be aware of that possibility).

Then, the events are routed to any still-registered entrants in the PointerRouter's table for that pointer.

When a PointerUpEvent is received, the GestureArenaManager.sweep method is invoked to force the gesture arena logic to terminate if necessary.

Superclass Constraints
Implements
Implemented by

Constructors

GestureBinding()

Properties

debugSamplingClock SamplingClock?
Overrides the sampling clock for debugging and testing. [...]
@protected, read-only
pointerRouter PointerRouter
A router that routes all pointer events received from the engine.
final
gestureArena GestureArenaManager
The gesture arenas used for disambiguating the meaning of sequences of pointer events.
final
pointerSignalResolver PointerSignalResolver
The resolver used for determining which widget handles a PointerSignalEvent.
final
resamplingEnabled bool
Enable pointer event resampling for touch devices by setting this to true. [...]
read / write
samplingOffset Duration
Offset relative to current frame time that should be used for resampling. The samplingOffset is expected to be negative. Non-negative samplingOffset is allowed but will effectively disable resampling.
read / write
window SingletonFlutterWindow
The main window to which this binding is bound. [...]
read-only, inherited
platformDispatcher PlatformDispatcher
The ui.PlatformDispatcher to which this binding is bound. [...]
read-only, inherited
locked bool
Whether lockEvents is currently locking events. [...]
@protected, read-only, inherited
hashCode int
The hash code for this object. [...]
read-only, inherited
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited

Methods

initInstances() → void
The initialization method. Subclasses override this method to hook into the platform and otherwise configure their services. Subclasses must call "super.initInstances()". [...]
override
unlocked() → void
Called by lockEvents when events get unlocked. [...]
override
cancelPointer(int pointer) → void
Dispatch a PointerCancelEvent for the given pointer soon. [...]
handlePointerEvent(PointerEvent event) → void
Dispatch an event to the targets found by a hit test on its position. [...]
hitTest(HitTestResult result, Offset position) → void
Determine which HitTestTarget objects are located at a given position.
override
dispatchEvent(PointerEvent event, HitTestResult? hitTestResult) → void
Dispatch an event to pointerRouter and the path of a hit test result. [...]
override
handleEvent(PointerEvent event, HitTestEntry entry) → void
Override this method to receive events.
override
resetGestureBinding() → void
Reset states of GestureBinding. [...]
initServiceExtensions() → void
Called when the binding is initialized, to register service extensions. [...]
@mustCallSuper, @protected, inherited
lockEvents(Future<void> callback()) Future<void>
Locks the dispatching of asynchronous events and callbacks until the callback's future completes. [...]
@protected, inherited
reassembleApplication() Future<void>
Cause the entire application to redraw, e.g. after a hot reload. [...]
inherited
performReassemble() Future<void>
This method is called by reassembleApplication to actually cause the application to reassemble, e.g. after a hot reload. [...]
@mustCallSuper, @protected, inherited
registerSignalServiceExtension({required String name, required AsyncCallback callback}) → void
Registers a service extension method with the given name (full name "ext.flutter.name"), which takes no arguments and returns no value. [...]
@protected, inherited
registerBoolServiceExtension({required String name, required AsyncValueGetter<bool> getter, required AsyncValueSetter<bool> setter}) → void
Registers a service extension method with the given name (full name "ext.flutter.name"), which takes a single argument "enabled" which can have the value "true" or the value "false" or can be omitted to read the current value. (Any value other than "true" is considered equivalent to "false". Other arguments are ignored.) [...]
@protected, inherited
registerNumericServiceExtension({required String name, required AsyncValueGetter<double> getter, required AsyncValueSetter<double> setter}) → void
Registers a service extension method with the given name (full name "ext.flutter.name"), which takes a single argument with the same name as the method which, if present, must have a value that can be parsed by double.parse, and can be omitted to read the current value. (Other arguments are ignored.) [...]
@protected, inherited
postEvent(String eventKind, Map<String, dynamic> eventData) → void
All events dispatched by a BindingBase use this method instead of calling developer.postEvent directly so that tests for BindingBase can track which events were dispatched by overriding this method.
@protected, inherited
registerStringServiceExtension({required String name, required AsyncValueGetter<String> getter, required AsyncValueSetter<String> setter}) → void
Registers a service extension method with the given name (full name "ext.flutter.name"), which optionally takes a single argument with the name "value". If the argument is omitted, the value is to be read, otherwise it is to be set. Returns the current value. [...]
@protected, inherited
registerServiceExtension({required String name, required ServiceExtensionCallback callback}) → void
Registers a service extension method with the given name (full name "ext.flutter.name"). [...]
@protected, inherited
toString() String
A string representation of this object. [...]
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
inherited

Operators

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

Static Properties

instance GestureBinding?
The singleton instance of this object.
read-only