Class AccessibilityBridge
- java.lang.Object
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- android.view.accessibility.AccessibilityNodeProvider
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- io.flutter.view.AccessibilityBridge
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public class AccessibilityBridge extends AccessibilityNodeProvider
Bridge between Android's OS accessibility system and Flutter's accessibility system.An
AccessibilityBridge
requires:- A real Android
View
, called therootAccessibilityView
, which contains a Flutter UI. TherootAccessibilityView
is required at the time ofAccessibilityBridge
's instantiation and is held for the duration ofAccessibilityBridge
's lifespan.AccessibilityBridge
invokes various accessibility methods on therootAccessibilityView
, e.g.,View.onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo)
. TherootAccessibilityView
is expected to notify theAccessibilityBridge
of relevant interactions:onAccessibilityHoverEvent(MotionEvent)
,reset()
,updateSemantics(ByteBuffer, String[], ByteBuffer[])
, andupdateCustomAccessibilityActions(ByteBuffer, String[])
- An
AccessibilityChannel
that is connected to the running Flutter app. - Android's
AccessibilityManager
to query and listen for accessibility settings. - Android's
ContentResolver
to listen for changes to system animation settings.
AccessibilityBridge
causes Android to treat FlutterSemanticsNode
s as if they were accessible AndroidView
s. Accessibility requests may be sent from a Flutter widget to the Android OS, as if it were an AndroidView
, and accessibility events may be consumed by a Flutter widget, as if it were an AndroidView
.AccessibilityBridge
refers to Flutter's accessible widgets as "virtual views" and identifies them with "virtual view IDs". - A real Android
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
AccessibilityBridge.Action
static interface
AccessibilityBridge.OnAccessibilityChangeListener
Listener that can be set on aAccessibilityBridge
, which is invoked any time accessibility is turned on/off, or touch exploration is turned on/off.
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Field Summary
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Fields inherited from class android.view.accessibility.AccessibilityNodeProvider
HOST_VIEW_ID
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Constructor Summary
Constructors Constructor Description AccessibilityBridge(View rootAccessibilityView, AccessibilityChannel accessibilityChannel, AccessibilityManager accessibilityManager, ContentResolver contentResolver, PlatformViewsAccessibilityDelegate platformViewsAccessibilityDelegate)
AccessibilityBridge(View rootAccessibilityView, AccessibilityChannel accessibilityChannel, AccessibilityManager accessibilityManager, ContentResolver contentResolver, io.flutter.view.AccessibilityViewEmbedder accessibilityViewEmbedder, PlatformViewsAccessibilityDelegate platformViewsAccessibilityDelegate)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description AccessibilityNodeInfo
createAccessibilityNodeInfo(int virtualViewId)
ReturnsAccessibilityNodeInfo
for the view corresponding to the givenvirtualViewId
.boolean
externalViewRequestSendAccessibilityEvent(View embeddedView, View eventOrigin, AccessibilityEvent event)
Delegates handling ofViewParent.requestSendAccessibilityEvent(android.view.View, android.view.accessibility.AccessibilityEvent)
to the accessibility bridge.AccessibilityNodeInfo
findFocus(int focus)
Finds the view in a hierarchy that currently has the given type offocus
.int
getHoveredObjectId()
boolean
isAccessibilityEnabled()
Returns true if the Android OS currently has accessibility enabled, false otherwise.boolean
isTouchExplorationEnabled()
Returns true if the Android OS currently has touch exploration enabled, false otherwise.AccessibilityNodeInfo
obtainAccessibilityNodeInfo(View rootView, int virtualViewId)
boolean
onAccessibilityHoverEvent(MotionEvent event)
boolean
performAction(int virtualViewId, int accessibilityAction, Bundle arguments)
Instructs the view represented byvirtualViewId
to carry out the desiredaccessibilityAction
, perhaps configured by additionalarguments
.void
release()
Disconnects any listeners and/or delegates that were initialized inAccessibilityBridge
's constructor, or added after.void
reset()
Resets theAccessibilityBridge
: ClearsflutterSemanticsTree
, the Android cache of Flutter's semantics tree Releases focus on any activeaccessibilityFocusedSemanticsNode
Clears any hoveredSemanticsNode
Sends aAccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED
eventvoid
setOnAccessibilityChangeListener(AccessibilityBridge.OnAccessibilityChangeListener listener)
Sets a listener on thisAccessibilityBridge
, which is notified whenever accessibility activation, or touch exploration activation changes.-
Methods inherited from class android.view.accessibility.AccessibilityNodeProvider
addExtraDataToAccessibilityNodeInfo, findAccessibilityNodeInfosByText
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Constructor Detail
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AccessibilityBridge
public AccessibilityBridge(@NonNull View rootAccessibilityView, @NonNull AccessibilityChannel accessibilityChannel, @NonNull AccessibilityManager accessibilityManager, @NonNull ContentResolver contentResolver, @NonNull PlatformViewsAccessibilityDelegate platformViewsAccessibilityDelegate)
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AccessibilityBridge
public AccessibilityBridge(@NonNull View rootAccessibilityView, @NonNull AccessibilityChannel accessibilityChannel, @NonNull AccessibilityManager accessibilityManager, @NonNull ContentResolver contentResolver, @NonNull io.flutter.view.AccessibilityViewEmbedder accessibilityViewEmbedder, @NonNull PlatformViewsAccessibilityDelegate platformViewsAccessibilityDelegate)
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Method Detail
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getHoveredObjectId
public int getHoveredObjectId()
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release
public void release()
Disconnects any listeners and/or delegates that were initialized inAccessibilityBridge
's constructor, or added after.Do not use this instance after invoking
release
. The behavior of any method invoked on thisAccessibilityBridge
after invokingrelease()
is undefined.
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isAccessibilityEnabled
public boolean isAccessibilityEnabled()
Returns true if the Android OS currently has accessibility enabled, false otherwise.
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isTouchExplorationEnabled
public boolean isTouchExplorationEnabled()
Returns true if the Android OS currently has touch exploration enabled, false otherwise.
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setOnAccessibilityChangeListener
public void setOnAccessibilityChangeListener(@Nullable AccessibilityBridge.OnAccessibilityChangeListener listener)
Sets a listener on thisAccessibilityBridge
, which is notified whenever accessibility activation, or touch exploration activation changes.
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obtainAccessibilityNodeInfo
public AccessibilityNodeInfo obtainAccessibilityNodeInfo(View rootView, int virtualViewId)
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createAccessibilityNodeInfo
public AccessibilityNodeInfo createAccessibilityNodeInfo(int virtualViewId)
ReturnsAccessibilityNodeInfo
for the view corresponding to the givenvirtualViewId
.This method is invoked by Android's accessibility system when Android needs accessibility info for a given view.
When a
virtualViewId
ofView.NO_ID
is requested, accessibility node info is returned for ourrootAccessibilityView
. Otherwise, Flutter's semantics tree, represented byflutterSemanticsTree
, is searched for aAccessibilityBridge.SemanticsNode
with the givenvirtualViewId
. If no suchAccessibilityBridge.SemanticsNode
is found, then this method returns null. If the desiredAccessibilityBridge.SemanticsNode
is found, then anAccessibilityNodeInfo
is obtained from therootAccessibilityView
, filled with appropriate info, and then returned.Depending on the type of Flutter
SemanticsNode
that is requested, the returnedAccessibilityNodeInfo
pretends that theSemanticsNode
in question comes from a specialize Android view, e.g.,AccessibilityBridge.Flag.IS_TEXT_FIELD
maps toandroid.widget.EditText
,AccessibilityBridge.Flag.IS_BUTTON
maps toandroid.widget.Button
, andAccessibilityBridge.Flag.IS_IMAGE
maps toandroid.widget.ImageView
. In the case that no specialized view applies, the returnedAccessibilityNodeInfo
pretends that it represents aandroid.view.View
.- Overrides:
createAccessibilityNodeInfo
in classAccessibilityNodeProvider
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performAction
public boolean performAction(int virtualViewId, int accessibilityAction, @Nullable Bundle arguments)
Instructs the view represented byvirtualViewId
to carry out the desiredaccessibilityAction
, perhaps configured by additionalarguments
.This method is invoked by Android's accessibility system. This method returns true if the desired
SemanticsNode
was found and was capable of performing the desired action, false otherwise.In a traditional Android app, the given view ID refers to a
View
within an AndroidView
hierarchy. Flutter does not have an AndroidView
hierarchy, therefore the given view ID is avirtualViewId
that refers to aSemanticsNode
within a Flutter app. The given arguments of this method are forwarded from Android to Flutter.- Overrides:
performAction
in classAccessibilityNodeProvider
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findFocus
public AccessibilityNodeInfo findFocus(int focus)
Finds the view in a hierarchy that currently has the given type offocus
.This method is invoked by Android's accessibility system.
Flutter does not have an Android
View
hierarchy. Therefore, Flutter conceptually handles this request by searching its semantics tree for the givenfocus
, represented byflutterSemanticsTree
. In practice, thisAccessibilityBridge
always caches any activeaccessibilityFocusedSemanticsNode
andinputFocusedSemanticsNode
. Therefore, no searching is necessary. This method directly inspects the givenfocus
type to return one of the cached nodes, null if the cached node is null, or null if a differentfocus
type is requested.- Overrides:
findFocus
in classAccessibilityNodeProvider
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onAccessibilityHoverEvent
public boolean onAccessibilityHoverEvent(MotionEvent event)
A hoverMotionEvent
has occurred in theView
that corresponds to thisAccessibilityBridge
.This method returns true if Flutter's accessibility system handled the hover event, false otherwise.
This method should be invoked from the corresponding
View
'sView.onHoverEvent(MotionEvent)
.
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reset
public void reset()
Resets theAccessibilityBridge
:- Clears
flutterSemanticsTree
, the Android cache of Flutter's semantics tree - Releases focus on any active
accessibilityFocusedSemanticsNode
- Clears any hovered
SemanticsNode
- Sends a
AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED
event
- Clears
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externalViewRequestSendAccessibilityEvent
public boolean externalViewRequestSendAccessibilityEvent(View embeddedView, View eventOrigin, AccessibilityEvent event)
Delegates handling ofViewParent.requestSendAccessibilityEvent(android.view.View, android.view.accessibility.AccessibilityEvent)
to the accessibility bridge.This is used by embedded platform views to propagate accessibility events from their view hierarchy to the accessibility bridge.
As the embedded view doesn't have to be the only View in the embedded hierarchy (it can have child views) and the event might have been originated from any view in this hierarchy, this method gets both a reference to the embedded platform view, and a reference to the view from its hierarchy that sent the event.
- Parameters:
embeddedView
- the embedded platform view for which the event is delegatedeventOrigin
- the view in the embedded view's hierarchy that sent the event.- Returns:
- True if the event was sent.
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