WidgetsFlutterBinding class Null safety

A concrete binding for applications based on the Widgets framework.

This is the glue that binds the framework to the Flutter engine.

When using the widgets framework, this binding, or one that implements the same interfaces, must be used. The following mixins are used to implement this binding:

GestureBinding, which implements the basics of hit testing.
SchedulerBinding, which introduces the concepts of frames.
ServicesBinding, which provides access to the plugin subsystem.
PaintingBinding, which enables decoding images.
SemanticsBinding, which supports accessibility.
RendererBinding, which handles the render tree.
WidgetsBinding, which handles the widget tree.

Inheritance

Object
BindingBase
WidgetsFlutterBinding

Mixed in types

Constructors

WidgetsFlutterBinding()

Properties

accessibilityFeatures → AccessibilityFeatures: The currently active set of AccessibilityFeatures.
read-onlyinherited
buildOwner → BuildOwner?: The BuildOwner in charge of executing the build pipeline for the widget tree rooted at this binding.
read-onlyinherited
channelBuffers → ChannelBuffers: The low level buffering and dispatch mechanism for messages sent by plugins on the engine side to their corresponding plugin code on the framework side.
read-onlyinherited
currentFrameTimeStamp → Duration: The time stamp for the frame currently being processed.
read-onlyinherited
currentSystemFrameTimeStamp → Duration: The raw time stamp as provided by the engine to dart:ui.PlatformDispatcher.onBeginFrame for the frame currently being processed.
read-onlyinherited
debugBuildingDirtyElements ↔ bool: Whether we are currently in a frame. This is used to verify that frames are not scheduled redundantly.
protected">@protectedread / writeinherited
debugDidSendFirstFrameEvent → bool: Whether the first frame has finished building.
read-onlyinherited
debugSamplingClock → SamplingClock?: Overrides the sampling clock for debugging and testing.
protected">@protectedread-onlyinherited
defaultBinaryMessenger → BinaryMessenger: The default instance of BinaryMessenger.
read-onlyinherited
disableAnimations → bool: The platform is requesting that animations be disabled or simplified.
read-onlyinherited
endOfFrame → Future<void>: Returns a Future that completes after the frame completes.
read-onlyinherited
firstFrameRasterized → bool: Whether the Flutter engine has rasterized the first frame.
read-onlyinherited
focusManager → FocusManager: The object in charge of the focus tree.
read-onlyinherited
framesEnabled → bool: Whether frames are currently being scheduled when scheduleFrame is called.
read-onlyinherited
gestureArena → GestureArenaManager: The gesture arenas used for disambiguating the meaning of sequences of pointer events.
finalinherited
hashCode → int: The hash code for this object.
read-onlyinherited
hasScheduledFrame → bool: Whether this scheduler has requested that handleBeginFrame be called soon.
read-onlyinherited
imageCache → ImageCache: The singleton that implements the Flutter framework's image cache.
read-onlyinherited
isRootWidgetAttached → bool: Whether the renderViewElement has been initialized.
read-onlyinherited
keyboard → HardwareKeyboard: The global singleton instance of HardwareKeyboard, which can be used to query keyboard states.
read-onlyinherited
keyEventManager → KeyEventManager: The global singleton instance of KeyEventManager, which is used internally to dispatch key messages.
read-onlyinherited
lifecycleState → AppLifecycleState?: Whether the application is visible, and if so, whether it is currently interactive.
read-onlyinherited
locked → bool: Whether lockEvents is currently locking events.
protected">@protectedread-onlyinherited
mouseTracker → MouseTracker: The object that manages state about currently connected mice, for hover notification.
read-onlyinherited
pipelineOwner → PipelineOwner: The render tree's owner, which maintains dirty state for layout, composite, paint, and accessibility semantics.
read-onlyinherited
platformDispatcher → PlatformDispatcher: The ui.PlatformDispatcher to which this binding is bound.
read-onlyinherited
platformMenuDelegate ↔ PlatformMenuDelegate: A delegate that communicates with a platform plugin for serializing and managing platform-rendered menu bars created by PlatformMenuBar.
read / writeinherited
pointerRouter → PointerRouter: A router that routes all pointer events received from the engine.
finalinherited
pointerSignalResolver → PointerSignalResolver: The resolver used for determining which widget handles a PointerSignalEvent.
finalinherited
renderView ↔ RenderView: The render tree that's attached to the output surface.
read / writeinherited
renderViewElement → Element?: The Element that is at the root of the hierarchy (and which wraps the RenderView object at the root of the rendering hierarchy).
read-onlyinherited
resamplingEnabled ↔ bool: Enable pointer event resampling for touch devices by setting this to true.
read / writeinherited
restorationManager → RestorationManager: The RestorationManager synchronizes the restoration data between engine and framework.
read-onlyinherited
runtimeType → Type: A representation of the runtime type of the object.
read-onlyinherited
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 / writeinherited
schedulerPhase → SchedulerPhase: The phase that the scheduler is currently operating under.
read-onlyinherited
schedulingStrategy ↔ SchedulingStrategy: The strategy to use when deciding whether to run a task or not.
read / writeinherited
sendFramesToEngine → bool: Whether frames produced by drawFrame are sent to the engine.
read-onlyinherited
systemFonts → Listenable: Listenable that notifies when the available fonts on the system have changed.
read-onlyinherited
transientCallbackCount → int: The current number of transient frame callbacks scheduled.
read-onlyinherited
waitUntilFirstFrameRasterized → Future<void>: A future that completes when the Flutter engine has rasterized the first frame.
read-onlyinherited
window → SingletonFlutterWindow: The main window to which this binding is bound.
read-onlyinherited

Methods

addObserver(WidgetsBindingObserver observer) → void: Registers the given object as a binding observer. Binding observers are notified when various application events occur, for example when the system locale changes. Generally, one widget in the widget tree registers itself as a binding observer, and converts the system state into inherited widgets.
inherited
addPersistentFrameCallback(FrameCallback callback) → void: Adds a persistent frame callback.
inherited
addPostFrameCallback(FrameCallback callback) → void: Schedule a callback for the end of this frame.
inherited
addTimingsCallback(TimingsCallback callback) → void: Add a TimingsCallback that receives FrameTiming sent from the engine.
inherited
allowFirstFrame() → void: Called after deferFirstFrame to tell the framework that it is ok to send the first frame to the engine now.
inherited
attachRootWidget(Widget rootWidget) → void: Takes a widget and attaches it to the renderViewElement, creating it if necessary.
inherited
cancelFrameCallbackWithId(int id) → void: Cancels the transient frame callback with the given id.
inherited
cancelPointer(int pointer) → void: Dispatch a PointerCancelEvent for the given pointer soon.
inherited
computePlatformResolvedLocale(List<Locale> supportedLocales) → Locale?: Computes the locale the current platform would resolve to.
inherited
createBinaryMessenger() → BinaryMessenger: Creates a default BinaryMessenger instance that can be used for sending platform messages.
protected">@protectedinherited
createImageCache() → ImageCache: Creates the ImageCache singleton (accessible via imageCache).
protected">@protectedinherited
createRestorationManager() → RestorationManager: Creates the RestorationManager instance available via restorationManager.
protected">@protectedinherited
createSemanticsUpdateBuilder() → SemanticsUpdateBuilder: Creates an empty semantics update builder.
inherited
createViewConfiguration() → ViewConfiguration: Returns a ViewConfiguration configured for the RenderView based on the current environment.
inherited
debugAssertNoTransientCallbacks(String reason) → bool: Asserts that there are no registered transient callbacks; if there are, prints their locations and throws an exception.
inherited
deferFirstFrame() → void: Tell the framework to not send the first frames to the engine until there is a corresponding call to allowFirstFrame.
inherited
dispatchAccessibilityFeaturesChanged() → void: Notify all the observers that the active set of AccessibilityFeatures has changed (using WidgetsBindingObserver.didChangeAccessibilityFeatures), giving them the features argument.
mustCallSuper">@mustCallSuperprotected">@protectedinherited
dispatchEvent(PointerEvent event, HitTestResult? hitTestResult) → void: Dispatch an event to pointerRouter and the path of a hit test result.
inherited
dispatchLocalesChanged(List<Locale>? locales) → void: Notify all the observers that the locale has changed (using WidgetsBindingObserver.didChangeLocales), giving them the locales argument.
mustCallSuper">@mustCallSuperprotected">@protectedinherited
drawFrame() → void: Pump the build and rendering pipeline to generate a frame.
inherited
ensureFrameCallbacksRegistered() → void: Ensures callbacks for PlatformDispatcher.onBeginFrame and PlatformDispatcher.onDrawFrame are registered.
protected">@protectedinherited
ensureVisualUpdate() → void: Schedules a new frame using scheduleFrame if this object is not currently producing a frame.
inherited
evict(String asset) → void: Called in response to the ext.flutter.evict service extension.
inherited
handleAccessibilityFeaturesChanged() → void: Called when the platform accessibility features change.
inherited
handleAppLifecycleStateChanged(AppLifecycleState state) → void: Called when the application lifecycle state changes.
inherited
handleBeginFrame(Duration? rawTimeStamp) → void: Called by the engine to prepare the framework to produce a new frame.
inherited
handleDrawFrame() → void: Called by the engine to produce a new frame.
inherited
handleEvent(PointerEvent event, HitTestEntry<HitTestTarget> entry) → void: Override this method to receive events.
inherited
handleEventLoopCallback() → bool: Execute the highest-priority task, if it is of a high enough priority.
visibleForTesting">@visibleForTestinginherited
handleLocaleChanged() → void: Called when the system locale changes.
mustCallSuper">@mustCallSuperprotected">@protectedinherited
handleMemoryPressure() → void: Called when the operating system notifies the application of a memory pressure situation.
inherited
handleMetricsChanged() → void: Called when the system metrics change.
inherited
handlePlatformBrightnessChanged() → void: Called when the platform brightness changes.
inherited
handlePointerEvent(PointerEvent event) → void: Dispatch an event to the targets found by a hit test on its position.
inherited
handlePopRoute() → Future<void>: Called when the system pops the current route.
protected">@protectedinherited
handlePushRoute(String route) → Future<void>: Called when the host tells the app to push a new route onto the navigator.
mustCallSuper">@mustCallSuperprotected">@protectedinherited
handleSystemMessage(Object systemMessage) → Future<void>: Handler called for messages received on the SystemChannels.system message channel.
inherited
handleTextScaleFactorChanged() → void: Called when the platform text scale factor changes.
inherited
hitTest(HitTestResult result, Offset position) → void: Determine which HitTestTarget objects are located at a given position.
inherited
initInstances() → void: The initialization method. Subclasses override this method to hook into the platform and otherwise configure their services. Subclasses must call "super.initInstances()".
inherited
initLicenses() → void: Adds relevant licenses to the LicenseRegistry.
mustCallSuper">@mustCallSuperprotected">@protectedinherited
initMouseTracker([MouseTracker? tracker]) → void: Creates a MouseTracker which manages state about currently connected mice, for hover notification.
visibleForTesting">@visibleForTestinginherited
initRenderView() → void: Creates a RenderView object to be the root of the RenderObject rendering tree, and initializes it so that it will be rendered when the next frame is requested.
inherited
initServiceExtensions() → void: Called when the binding is initialized, to register service extensions.
inherited
instantiateImageCodec(Uint8List bytes, {int? cacheWidth, int? cacheHeight, bool allowUpscaling = false}) → Future<Codec>: Calls through to dart:ui.instantiateImageCodec from ImageCache.
Deprecated('Use instantiateImageCodecFromBuffer with an ImmutableBuffer instance instead. ' 'This feature was deprecated after v2.13.0-1.0.pre.')">@Deprecated('Use instantiateImageCodecFromBuffer with an ImmutableBuffer instance instead. ' 'This feature was deprecated after v2.13.0-1.0.pre.')inherited
instantiateImageCodecFromBuffer(ImmutableBuffer buffer, {int? cacheWidth, int? cacheHeight, bool allowUpscaling = false}) → Future<Codec>: Calls through to dart:ui.instantiateImageCodecFromBuffer from ImageCache.
inherited
lockEvents(Future<void> callback()) → Future<void>: Locks the dispatching of asynchronous events and callbacks until the callback's future completes.
protected">@protectedinherited
noSuchMethod(Invocation invocation) → dynamic: Invoked when a non-existent method or property is accessed.
inherited
performReassemble() → Future<void>: This method is called by reassembleApplication to actually cause the application to reassemble, e.g. after a hot reload.
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">@protectedinherited
readInitialLifecycleStateFromNativeWindow() → void: Initializes the lifecycleState with the dart:ui.PlatformDispatcher.initialLifecycleState.
protected">@protectedinherited
reassembleApplication() → Future<void>: Cause the entire application to redraw, e.g. after a hot reload.
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">@protectedinherited
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">@protectedinherited
registerServiceExtension({required String name, required ServiceExtensionCallback callback}) → void: Registers a service extension method with the given name (full name "ext.flutter.name").
protected">@protectedinherited
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">@protectedinherited
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">@protectedinherited
removeObserver(WidgetsBindingObserver observer) → bool: Unregisters the given observer. This should be used sparingly as it is relatively expensive (O(N) in the number of registered observers).
inherited
removeTimingsCallback(TimingsCallback callback) → void: Removes a callback that was earlier added by addTimingsCallback.
inherited
resetEpoch() → void: Prepares the scheduler for a non-monotonic change to how time stamps are calculated.
inherited
resetFirstFrameSent() → void: Call this to pretend that no frames have been sent to the engine yet.
inherited
resetGestureBinding() → void: Reset states of GestureBinding.
protected">@protectedinherited
scheduleAttachRootWidget(Widget rootWidget) → void: Schedules a Timer for attaching the root widget.
protected">@protectedinherited
scheduleForcedFrame() → void: Schedules a new frame by calling dart:ui.PlatformDispatcher.scheduleFrame.
inherited
scheduleFrame() → void: If necessary, schedules a new frame by calling dart:ui.PlatformDispatcher.scheduleFrame.
inherited
scheduleFrameCallback(FrameCallback callback, {bool rescheduling = false}) → int: Schedules the given transient frame callback.
inherited
scheduleTask<T>(TaskCallback<T> task, Priority priority, {String? debugLabel, Flow? flow}) → Future<T>: Schedules the given task with the given priority and returns a Future that completes to the task's eventual return value.
inherited
scheduleWarmUpFrame() → void: Schedule a frame to run as soon as possible, rather than waiting for the engine to request a frame in response to a system "Vsync" signal.
inherited
setSemanticsEnabled(bool enabled) → void: Whether the render tree associated with this binding should produce a tree of SemanticsNode objects.
inherited
setSystemUiChangeCallback(SystemUiChangeCallback? callback) → void: Sets the callback for the SystemChrome.systemUIChange method call received on the SystemChannels.platform channel.
inherited
toString() → String: A string representation of this object.
inherited
unlocked() → void: Called by lockEvents when events get unlocked.
inherited

Operators

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

Static Methods

ensureInitialized() → WidgetsBinding: Returns an instance of the binding that implements WidgetsBinding. If no binding has yet been initialized, the WidgetsFlutterBinding class is used to create and initialize one.