WidgetsBinding mixin

The glue between the widgets layer and the Flutter engine.

Superclass Constraints
Implemented by




buildOwner BuildOwner
The BuildOwner in charge of executing the build pipeline for the widget tree rooted at this binding.
debugBuildingDirtyElements bool
Whether we are currently in a frame. This is used to verify that frames are not scheduled redundantly. [...]
@protected, read / write
debugDidSendFirstFrameEvent bool
Whether the first frame has finished building. [...]
firstFrameRasterized bool
Whether the Flutter engine has rasterized the first frame. [...]
focusManager FocusManager
The object in charge of the focus tree. [...]
isRootWidgetAttached bool
Whether the renderViewElement has been initialized. [...]
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). [...]
waitUntilFirstFrameRasterized Future<void>
A future that completes when the Flutter engine has rasterized the first frame. [...]
accessibilityFeatures AccessibilityFeatures
The currently active set of AccessibilityFeatures. [...]
read-only, inherited
currentFrameTimeStamp Duration
The time stamp for the frame currently being processed. [...]
read-only, inherited
currentSystemFrameTimeStamp Duration
The raw time stamp as provided by the engine to Window.onBeginFrame for the frame currently being processed. [...]
read-only, inherited
disableAnimations bool
The platform is requesting that animations be disabled or simplified. [...]
read-only, inherited
endOfFrame Future<void>
Returns a Future that completes after the frame completes. [...]
read-only, inherited
framesEnabled bool
Whether frames are currently being scheduled when scheduleFrame is called. [...]
read-only, inherited
gestureArena GestureArenaManager
The gesture arenas used for disambiguating the meaning of sequences of pointer events.
final, inherited
hashCode int
The hash code for this object. [...]
read-only, inherited
hasScheduledFrame bool
Whether this scheduler has requested that handleBeginFrame be called soon.
read-only, inherited
lifecycleState AppLifecycleState
Whether the application is visible, and if so, whether it is currently interactive. [...]
read-only, inherited
locked bool
Whether lockEvents is currently locking events. [...]
@protected, read-only, inherited
mouseTracker MouseTracker
The object that manages state about currently connected mice, for hover notification.
read-only, inherited
pipelineOwner PipelineOwner
The render tree's owner, which maintains dirty state for layout, composite, paint, and accessibility semantics
read-only, inherited
pointerRouter PointerRouter
A router that routes all pointer events received from the engine.
final, inherited
pointerSignalResolver PointerSignalResolver
The resolver used for determining which widget handles a pointer signal event.
final, inherited
renderView RenderView
The render tree that's attached to the output surface.
read / write, inherited
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited
schedulerPhase SchedulerPhase
The phase that the scheduler is currently operating under.
read-only, inherited
schedulingStrategy SchedulingStrategy
The strategy to use when deciding whether to run a task or not. [...]
read / write, inherited
transientCallbackCount int
The current number of transient frame callbacks scheduled. [...]
read-only, inherited
window Window
The window to which this binding is bound. [...]
read-only, inherited


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. [...]
allowFirstFrameReport() → void
When called after deferFirstFrameReport: tell the framework to report the frame it is building as a "useful" first frame. [...]
attachRootWidget(Widget rootWidget) → void
Takes a widget and attaches it to the renderViewElement, creating it if necessary. [...]
deferFirstFrameReport() → void
Tell the framework not to report the frame it is building as a "useful" first frame until there is a corresponding call to allowFirstFrameReport. [...]
dispatchAccessibilityFeaturesChanged() → void
Notify all the observers that the active set of AccessibilityFeatures has changed (using WidgetsBindingObserver.didChangeAccessibilityFeatures), giving them the features argument. [...]
@mustCallSuper, @protected
dispatchLocalesChanged(List<Locale> locales) → void
Notify all the observers that the locale has changed (using WidgetsBindingObserver.didChangeLocales), giving them the locales argument. [...]
@mustCallSuper, @protected
drawFrame() → void
Pump the build and rendering pipeline to generate a frame. [...]
handleAccessibilityFeaturesChanged() → void
Called when the platform accessibility features change. [...]
handleAppLifecycleStateChanged(AppLifecycleState state) → void
Called when the application lifecycle state changes. [...]
handleLocaleChanged() → void
Called when the system locale changes. [...]
@mustCallSuper, @protected
handleMemoryPressure() → void
Called when the operating system notifies the application of a memory pressure situation. [...]
handleMetricsChanged() → void
Called when the system metrics change. [...]
handlePlatformBrightnessChanged() → void
Called when the platform brightness changes. [...]
handlePopRoute() Future<void>
Called when the system pops the current route. [...]
handlePushRoute(String route) Future<void>
Called when the host tells the app to push a new route onto the navigator. [...]
@mustCallSuper, @protected
handleTextScaleFactorChanged() → void
Called when the platform text scale factor changes. [...]
initInstances() → void
The initialization method. Subclasses override this method to hook into the platform and otherwise configure their services. Subclasses must call "super.initInstances()". [...]
initServiceExtensions() → void
Called when the binding is initialized, to register service extensions. [...]
performReassemble() Future<void>
This method is called by reassembleApplication to actually cause the application to reassemble, e.g. after a hot reload. [...]
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). [...]
addPersistentFrameCallback(FrameCallback callback) → void
Adds a persistent frame callback. [...]
addPostFrameCallback(FrameCallback callback) → void
Schedule a callback for the end of this frame. [...]
cancelFrameCallbackWithId(int id) → void
Cancels the transient frame callback with the given id. [...]
cancelPointer(int pointer) → void
Dispatch a PointerCancelEvent for the given pointer soon. [...]
createViewConfiguration() ViewConfiguration
Returns a ViewConfiguration configured for the RenderView based on the current environment. [...]
debugAssertNoTransientCallbacks(String reason) bool
Asserts that there are no registered transient callbacks; if there are, prints their locations and throws an exception. [...]
dispatchEvent(PointerEvent event, HitTestResult hitTestResult) → void
Dispatch an event to a hit test result's path. [...]
ensureVisualUpdate() → void
Schedules a new frame using scheduleFrame if this object is not currently producing a frame. [...]
evict(String asset) → void
Called in response to the ext.flutter.evict service extension. [...]
@mustCallSuper, @protected, inherited
handleBeginFrame(Duration rawTimeStamp) → void
Called by the engine to prepare the framework to produce a new frame. [...]
handleDrawFrame() → void
Called by the engine to produce a new frame. [...]
handleEvent(PointerEvent event, HitTestEntry entry) → void
Override this method to receive events.
handleEventLoopCallback() bool
Execute the highest-priority task, if it is of a high enough priority. [...]
@visibleForTesting, inherited
hitTest(HitTestResult result, Offset position) → void
Determine which HitTestTarget objects are located at a given position.
initLicenses() → void
Adds relevant licenses to the LicenseRegistry. [...]
@mustCallSuper, @protected, inherited
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 engine is next ready to display a frame. [...]
lockEvents(Future<void> callback()) Future<void>
Locks the dispatching of asynchronous events and callbacks until the callback's future completes. [...]
@protected, inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
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
readInitialLifecycleStateFromNativeWindow() → void
Initializes the lifecycleState with the initialLifecycleState from the window. [...]
@protected, inherited
reassembleApplication() Future<void>
Cause the entire application to redraw, e.g. after a hot reload. [...]
registerBoolServiceExtension({String name, AsyncValueGetter<bool> getter, 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({String name, AsyncValueGetter<double> getter, 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
registerServiceExtension({String name, ServiceExtensionCallback callback }) → void
Registers a service extension method with the given name (full name "ext.flutter.name"). [...]
@protected, inherited
registerSignalServiceExtension({String name, 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
registerStringServiceExtension({String name, AsyncValueGetter<String> getter, 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
resetEpoch() → void
Prepares the scheduler for a non-monotonic change to how time stamps are calculated. [...]
scheduleForcedFrame() → void
Schedules a new frame by calling Window.scheduleFrame. [...]
scheduleFrame() → void
If necessary, schedules a new frame by calling Window.scheduleFrame. [...]
scheduleFrameCallback(FrameCallback callback, { bool rescheduling: false }) int
Schedules the given transient frame callback. [...]
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. [...]
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. [...]
setSemanticsEnabled(bool enabled) → void
Whether the render tree associated with this binding should produce a tree of SemanticsNode objects.
toString() String
Returns a string representation of this object.
unlocked() → void
Called by lockEvents when events get unlocked. [...]
@mustCallSuper, @protected, inherited


operator ==(dynamic other) bool
The equality operator. [...]

Static Properties

instance WidgetsBinding
The current WidgetsBinding, if one has been created. [...]