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ExploreByTouchHelper

public abstract class ExploreByTouchHelper
extends AccessibilityDelegateCompat

java.lang.Object
↳	android.support.v4.view.AccessibilityDelegateCompat
	↳	android.support.v4.widget.ExploreByTouchHelper

ExploreByTouchHelper is a utility class for implementing accessibility support in custom Views that represent a collection of View-like logical items. It extends AccessibilityNodeProviderCompat and simplifies many aspects of providing information to accessibility services and managing accessibility focus. This class does not currently support hierarchies of logical items.

Clients should override abstract methods on this class and attach it to the host view using setAccessibilityDelegate(View, AccessibilityDelegateCompat):

 class MyCustomView extends View {
     private MyVirtualViewHelper mVirtualViewHelper;

     public MyCustomView(Context context, ...) {
         ...
         mVirtualViewHelper = new MyVirtualViewHelper(this);
         ViewCompat.setAccessibilityDelegate(this, mVirtualViewHelper);
     }

     @Override
     public boolean dispatchHoverEvent(MotionEvent event) {
       return mHelper.dispatchHoverEvent(this, event)
           || super.dispatchHoverEvent(event);
     }

     @Override
     public boolean dispatchKeyEvent(KeyEvent event) {
       return mHelper.dispatchKeyEvent(event)
           || super.dispatchKeyEvent(event);
     }

     @Override
     public boolean onFocusChanged(boolean gainFocus, int direction,
         Rect previouslyFocusedRect) {
       super.onFocusChanged(gainFocus, direction, previouslyFocusedRect);
       mHelper.onFocusChanged(gainFocus, direction, previouslyFocusedRect);
     }
 }
 mAccessHelper = new MyExploreByTouchHelper(someView);
 ViewCompat.setAccessibilityDelegate(someView, mAccessHelper);

Summary

Constants
`int`	`HOST_ID` Virtual node identifier value for the host view's node.
`int`	`INVALID_ID` Virtual node identifier value for invalid nodes.

Public constructors
`ExploreByTouchHelper(View host)` Constructs a new helper that can expose a virtual view hierarchy for the specified host view.

Public methods
`final boolean`	`clearKeyboardFocusForVirtualView(int virtualViewId)` Attempts to clear keyboard focus from a virtual view.
`final boolean`	`dispatchHoverEvent(MotionEvent event)` Delegates hover events from the host view.
`final boolean`	`dispatchKeyEvent(KeyEvent event)` Delegates key events from the host view.
`final int`	`getAccessibilityFocusedVirtualViewId()`
`AccessibilityNodeProviderCompat`	`getAccessibilityNodeProvider(View host)` Gets the provider for managing a virtual view hierarchy rooted at this View and reported to `AccessibilityService`s that explore the window content.
`int`	`getFocusedVirtualView()` This method is deprecated. Use `getAccessibilityFocusedVirtualViewId()`.
`final int`	`getKeyboardFocusedVirtualViewId()`
`final void`	`invalidateRoot()` Notifies the accessibility framework that the properties of the parent view have changed.
`final void`	`invalidateVirtualView(int virtualViewId)` Notifies the accessibility framework that the properties of a particular item have changed.
`final void`	`invalidateVirtualView(int virtualViewId, int changeTypes)` Notifies the accessibility framework that the properties of a particular item have changed.
`final void`	`onFocusChanged(boolean gainFocus, int direction, Rect previouslyFocusedRect)` Delegates focus changes from the host view.
`void`	`onInitializeAccessibilityEvent(View host, AccessibilityEvent event)` Initializes an `AccessibilityEvent` with information about the the host View which is the event source.
`void`	`onInitializeAccessibilityNodeInfo(View host, AccessibilityNodeInfoCompat info)` Initializes an `AccessibilityNodeInfoCompat` with information about the host view.
`final boolean`	`requestKeyboardFocusForVirtualView(int virtualViewId)` Attempts to give keyboard focus to a virtual view.
`final boolean`	`sendEventForVirtualView(int virtualViewId, int eventType)` Populates an event of the specified type with information about an item and attempts to send it up through the view hierarchy.

Protected methods
`abstract int`	`getVirtualViewAt(float x, float y)` Provides a mapping between view-relative coordinates and logical items.
`abstract void`	`getVisibleVirtualViews(List<Integer> virtualViewIds)` Populates a list with the view's visible items.
`abstract boolean`	`onPerformActionForVirtualView(int virtualViewId, int action, Bundle arguments)` Performs the specified accessibility action on the item associated with the virtual view identifier.
`void`	`onPopulateEventForHost(AccessibilityEvent event)` Populates an `AccessibilityEvent` with information about the host view.
`void`	`onPopulateEventForVirtualView(int virtualViewId, AccessibilityEvent event)` Populates an `AccessibilityEvent` with information about the specified item.
`void`	`onPopulateNodeForHost(AccessibilityNodeInfoCompat node)` Populates an `AccessibilityNodeInfoCompat` with information about the host view.
`abstract void`	`onPopulateNodeForVirtualView(int virtualViewId, AccessibilityNodeInfoCompat node)` Populates an `AccessibilityNodeInfoCompat` with information about the specified item.
`void`	`onVirtualViewKeyboardFocusChanged(int virtualViewId, boolean hasFocus)` Called when the focus state of a virtual view changes.

Inherited methods

From class


  
    android.support.v4.view.AccessibilityDelegateCompat

From class


  
    java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long millis, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void`	`wait(long millis)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void`	`wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.

Constants

HOST_ID

int HOST_ID

Virtual node identifier value for the host view's node.

Constant Value: -1 (0xffffffff)

INVALID_ID

int INVALID_ID

Virtual node identifier value for invalid nodes.

Constant Value: -2147483648 (0x80000000)

Public constructors

ExploreByTouchHelper

ExploreByTouchHelper (View host)

Constructs a new helper that can expose a virtual view hierarchy for the specified host view.

Parameters
`host`	`View`: view whose virtual view hierarchy is exposed by this helper

Public methods

clearKeyboardFocusForVirtualView

boolean clearKeyboardFocusForVirtualView (int virtualViewId)

Attempts to clear keyboard focus from a virtual view.

Parameters
`virtualViewId`	`int`: the identifier of the virtual view from which to clear keyboard focus

Returns
`boolean`	whether this virtual view actually cleared keyboard focus

dispatchHoverEvent

boolean dispatchHoverEvent (MotionEvent event)

Delegates hover events from the host view.

Dispatches hover MotionEvents to the virtual view hierarchy when the Explore by Touch feature is enabled.

This method should be called by overriding the host view's dispatchHoverEvent(MotionEvent) method:

@Override
 public boolean dispatchHoverEvent(MotionEvent event) {
   return mHelper.dispatchHoverEvent(this, event)
       || super.dispatchHoverEvent(event);
 }

Parameters
`event`	`MotionEvent`: The hover event to dispatch to the virtual view hierarchy.

Returns
`boolean`	Whether the hover event was handled.

dispatchKeyEvent

boolean dispatchKeyEvent (KeyEvent event)

Delegates key events from the host view.

This method should be called by overriding the host view's dispatchKeyEvent(KeyEvent) method:

@Override
 public boolean dispatchKeyEvent(KeyEvent event) {
   return mHelper.dispatchKeyEvent(event)
       || super.dispatchKeyEvent(event);
 }

Parameters
`event`	`KeyEvent`

Returns
`boolean`

getAccessibilityFocusedVirtualViewId

int getAccessibilityFocusedVirtualViewId ()

Returns
`int`	the identifier of the virtual view that has accessibility focus or `INVALID_ID` if no virtual view has accessibility focus

getAccessibilityNodeProvider

AccessibilityNodeProviderCompat getAccessibilityNodeProvider (View host)

Gets the provider for managing a virtual view hierarchy rooted at this View and reported to AccessibilityServices that explore the window content.

The default implementation behaves as ViewCompat#getAccessibilityNodeProvider(View) for the case of no accessibility delegate been set.

Parameters
`host`	`View`

Returns
`AccessibilityNodeProviderCompat`	The provider.

getFocusedVirtualView

int getFocusedVirtualView ()

This method is deprecated.
Use getAccessibilityFocusedVirtualViewId().

Returns the virtual view ID for the currently accessibility focused item.

Returns
`int`	the identifier of the virtual view that has accessibility focus or `INVALID_ID` if no virtual view has accessibility focus

getKeyboardFocusedVirtualViewId

int getKeyboardFocusedVirtualViewId ()

Returns
`int`	the identifier of the virtual view that has keyboard focus or `INVALID_ID` if no virtual view has keyboard focus

invalidateRoot

void invalidateRoot ()

Notifies the accessibility framework that the properties of the parent view have changed.

You must call this method after adding or removing items from the parent view.

invalidateVirtualView

void invalidateVirtualView (int virtualViewId)

Notifies the accessibility framework that the properties of a particular item have changed.

You must call this method after changing any of the properties set in onPopulateNodeForVirtualView(int, AccessibilityNodeInfoCompat).

Parameters
`virtualViewId`	`int`: the virtual view id to invalidate, or `HOST_ID` to invalidate the root view

See also:

invalidateVirtualView(int, int)

invalidateVirtualView

void invalidateVirtualView (int virtualViewId, 
                int changeTypes)

Notifies the accessibility framework that the properties of a particular item have changed.

You must call this method after changing any of the properties set in onPopulateNodeForVirtualView(int, AccessibilityNodeInfoCompat).

Parameters
`virtualViewId`	`int`: the virtual view id to invalidate, or `HOST_ID` to invalidate the root view
`changeTypes`	`int`: the bit mask of change types. May be `0` for the default (undefined) change type or one or more of: `CONTENT_CHANGE_TYPE_CONTENT_DESCRIPTION` `CONTENT_CHANGE_TYPE_SUBTREE` `CONTENT_CHANGE_TYPE_TEXT` `CONTENT_CHANGE_TYPE_UNDEFINED`

onFocusChanged

void onFocusChanged (boolean gainFocus, 
                int direction, 
                Rect previouslyFocusedRect)

Delegates focus changes from the host view.

This method should be called by overriding the host view's onFocusChanged(boolean, int, Rect) method:

@Override
 public boolean onFocusChanged(boolean gainFocus, int direction,
     Rect previouslyFocusedRect) {
   super.onFocusChanged(gainFocus, direction, previouslyFocusedRect);
   mHelper.onFocusChanged(gainFocus, direction, previouslyFocusedRect);
 }

Parameters
`gainFocus`	`boolean`
`direction`	`int`
`previouslyFocusedRect`	`Rect`

onInitializeAccessibilityEvent

void onInitializeAccessibilityEvent (View host, 
                AccessibilityEvent event)

Initializes an AccessibilityEvent with information about the the host View which is the event source.

The default implementation behaves as ViewCompat#onInitalizeAccessibilityEvent(View v, AccessibilityEvent event) for the case of no accessibility delegate been set.

Parameters
`host`	`View`: The View hosting the delegate.
`event`	`AccessibilityEvent`: The event to initialize.

onInitializeAccessibilityNodeInfo

void onInitializeAccessibilityNodeInfo (View host, 
                AccessibilityNodeInfoCompat info)

Initializes an AccessibilityNodeInfoCompat with information about the host view.

The default implementation behaves as ViewCompat#onInitializeAccessibilityNodeInfo(View, AccessibilityNodeInfoCompat) for the case of no accessibility delegate been set.

Parameters
`host`	`View`: The View hosting the delegate.
`info`	`AccessibilityNodeInfoCompat`: The instance to initialize.

requestKeyboardFocusForVirtualView

boolean requestKeyboardFocusForVirtualView (int virtualViewId)

Attempts to give keyboard focus to a virtual view.

Parameters
`virtualViewId`	`int`: the identifier of the virtual view on which to place keyboard focus

Returns
`boolean`	whether this virtual view actually took keyboard focus

sendEventForVirtualView

boolean sendEventForVirtualView (int virtualViewId, 
                int eventType)

Populates an event of the specified type with information about an item and attempts to send it up through the view hierarchy.

You should call this method after performing a user action that normally fires an accessibility event, such as clicking on an item.

public void performItemClick(T item) {
   ...
   sendEventForVirtualViewId(item.id, AccessibilityEvent.TYPE_VIEW_CLICKED);
 }

Parameters
`virtualViewId`	`int`: the identifier of the virtual view for which to send an event
`eventType`	`int`: the type of event to send

Returns
`boolean`	`true` if the event was sent successfully, `false` otherwise

Protected methods

getVirtualViewAt

int getVirtualViewAt (float x, 
                float y)

Provides a mapping between view-relative coordinates and logical items.

Parameters
`x`	`float`: The view-relative x coordinate
`y`	`float`: The view-relative y coordinate

Returns
`int`	virtual view identifier for the logical item under coordinates (x,y) or `HOST_ID` if there is no item at the given coordinates

getVisibleVirtualViews

void getVisibleVirtualViews (List<Integer> virtualViewIds)

Populates a list with the view's visible items. The ordering of items within virtualViewIds specifies order of accessibility focus traversal.

Parameters
`virtualViewIds`	`List`: The list to populate with visible items

onPerformActionForVirtualView

boolean onPerformActionForVirtualView (int virtualViewId, 
                int action, 
                Bundle arguments)

Performs the specified accessibility action on the item associated with the virtual view identifier. See performAction(int, Bundle) for more information.

Implementations must handle any actions added manually in onPopulateNodeForVirtualView(int, AccessibilityNodeInfoCompat).

The helper class automatically handles focus management resulting from ACTION_ACCESSIBILITY_FOCUS and ACTION_CLEAR_ACCESSIBILITY_FOCUS actions.

Parameters
`virtualViewId`	`int`: The virtual view identifier of the item on which to perform the action
`action`	`int`: The accessibility action to perform
`arguments`	`Bundle`: (Optional) A bundle with additional arguments, or null

Returns
`boolean`	true if the action was performed

onPopulateEventForHost

void onPopulateEventForHost (AccessibilityEvent event)

Populates an AccessibilityEvent with information about the host view.

The default implementation is a no-op.

Parameters
`event`	`AccessibilityEvent`: the event to populate with information about the host view

onPopulateEventForVirtualView

void onPopulateEventForVirtualView (int virtualViewId, 
                AccessibilityEvent event)

Populates an AccessibilityEvent with information about the specified item.

The helper class automatically populates the following fields based on the values set by onPopulateNodeForVirtualView(int, AccessibilityNodeInfoCompat), but implementations may optionally override them:

event text, see getText()
content description, see setContentDescription(CharSequence)
scrollability, see setScrollable(boolean)
password state, see setPassword(boolean)
enabled state, see setEnabled(boolean)
checked state, see setChecked(boolean)

The following required fields are automatically populated by the helper class and may not be overridden:

item class name, set to the value used in onPopulateNodeForVirtualView(int, AccessibilityNodeInfoCompat)
package name, set to the package of the host view's Context, see setPackageName(CharSequence)
event source, set to the host view and virtual view identifier, see setSource(View, int)

Parameters
`virtualViewId`	`int`: The virtual view id for the item for which to populate the event
`event`	`AccessibilityEvent`: The event to populate

onPopulateNodeForHost

void onPopulateNodeForHost (AccessibilityNodeInfoCompat node)

Populates an AccessibilityNodeInfoCompat with information about the host view.

The default implementation is a no-op.

Parameters
`node`	`AccessibilityNodeInfoCompat`: the node to populate with information about the host view

onPopulateNodeForVirtualView

void onPopulateNodeForVirtualView (int virtualViewId, 
                AccessibilityNodeInfoCompat node)

Populates an AccessibilityNodeInfoCompat with information about the specified item.

Implementations must populate the following required fields:

event text, see setText(CharSequence) or setContentDescription(CharSequence)
bounds in parent coordinates, see setBoundsInParent(Rect)

The helper class automatically populates the following fields with default values, but implementations may optionally override them:

enabled state, set to true, see setEnabled(boolean)
keyboard focusability, set to true, see setFocusable(boolean)
item class name, set to android.view.View, see setClassName(CharSequence)

The following required fields are automatically populated by the helper class and may not be overridden:

package name, identical to the package name set by onPopulateEventForVirtualView(int, AccessibilityEvent), see setPackageName(CharSequence)
node source, identical to the event source set in onPopulateEventForVirtualView(int, AccessibilityEvent), see setSource(View, int)
parent view, set to the host view, see setParent(View)
visibility, computed based on parent-relative bounds, see setVisibleToUser(boolean)
accessibility focus, computed based on internal helper state, see setAccessibilityFocused(boolean)
keyboard focus, computed based on internal helper state, see setFocused(boolean)
bounds in screen coordinates, computed based on host view bounds, see setBoundsInScreen(Rect)

Additionally, the helper class automatically handles keyboard focus and accessibility focus management by adding the appropriate ACTION_FOCUS, ACTION_CLEAR_FOCUS, ACTION_ACCESSIBILITY_FOCUS, or ACTION_CLEAR_ACCESSIBILITY_FOCUS actions. Implementations must never manually add these actions.

The helper class also automatically modifies parent- and screen-relative bounds to reflect the portion of the item visible within its parent.

Parameters
`virtualViewId`	`int`: The virtual view identifier of the item for which to populate the node
`node`	`AccessibilityNodeInfoCompat`: The node to populate

onVirtualViewKeyboardFocusChanged

void onVirtualViewKeyboardFocusChanged (int virtualViewId, 
                boolean hasFocus)

Called when the focus state of a virtual view changes.

Parameters
`virtualViewId`	`int`: the virtual view identifier
`hasFocus`	`boolean`: `true` if the view has focus, `false` otherwise