ExploreByTouchHelper

public static final int HOST_ID = -1

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

public static final int INVALID_ID = -2147483648

Virtual node identifier value for invalid nodes.

public ExploreByTouchHelper(@NonNull View host)

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

public final boolean clearKeyboardFocusForVirtualView(int virtualViewId)

Attempts to clear keyboard focus from a virtual view.

public final boolean dispatchHoverEvent(@NonNull 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 method:

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

public final boolean dispatchKeyEvent(@NonNull KeyEvent event)

Delegates key events from the host view.

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

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

public 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.

public int getFocusedVirtualView()

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

public final 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.

public final 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.

public final 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.

public final void onFocusChanged(
    boolean gainFocus,
    int direction,
    @Nullable Rect previouslyFocusedRect
)

Delegates focus changes from the host view.

This method should be called by overriding the host view's onFocusChanged method:

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

public 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.

public 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.

public final boolean requestKeyboardFocusForVirtualView(int virtualViewId)

Attempts to give keyboard focus to a virtual view.

public 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.

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);
}

public final void setBoundsInScreenFromBoundsInParent(
    @NonNull AccessibilityNodeInfoCompat node,
    @NonNull Rect boundsInParent
)

Calculates and assigns screen-relative bounds based on bounds in parent. Instead of calling the deprecated setBoundsInParent, it provides a convenient method to calculate and assign setBoundsInScreen based on boundsInParent.

protected abstract int getVirtualViewAt(float x, float y)

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

protected abstract 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.

protected abstract boolean onPerformActionForVirtualView(
    int virtualViewId,
    int action,
    @Nullable Bundle arguments
)

Performs the specified accessibility action on the item associated with the virtual view identifier. See performAction for more information.

Implementations must handle any actions added manually in onPopulateNodeForVirtualView.

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

protected void onPopulateEventForHost(@NonNull AccessibilityEvent event)

Populates an AccessibilityEvent with information about the host view.

The default implementation is a no-op.

protected void onPopulateEventForVirtualView(
    int virtualViewId,
    @NonNull 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, but implementations may optionally override them:

• event text, see getText
• content description, see setContentDescription
• scrollability, see setScrollable
• password state, see setPassword
• enabled state, see setEnabled
• checked state, see setChecked

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
• package name, set to the package of the host view's Context, see setPackageName
• event source, set to the host view and virtual view identifier, see setSource

protected void onPopulateNodeForHost(@NonNull AccessibilityNodeInfoCompat node)

Populates an AccessibilityNodeInfoCompat with information about the host view.

The default implementation is a no-op.

protected abstract void onPopulateNodeForVirtualView(
    int virtualViewId,
    @NonNull AccessibilityNodeInfoCompat node
)

Populates an AccessibilityNodeInfoCompat with information about the specified item.

Implementations must populate the following required fields:

• event text, see setText or setContentDescription
• bounds in screen coordinates, see setBoundsInScreen and (AccessibilityNodeInfoCompat, 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
• keyboard focusability, set to true, see setFocusable
• item class name, set to android.view.View, see setClassName

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, see setPackageName
• node source, identical to the event source set in onPopulateEventForVirtualView, see setSource
• parent view, set to the host view, see setParent
• visibility, computed based on parent-relative bounds, see setVisibleToUser
• accessibility focus, computed based on internal helper state, see setAccessibilityFocused
• keyboard focus, computed based on internal helper state, see setFocused

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.

protected void onVirtualViewKeyboardFocusChanged(int virtualViewId, boolean hasFocus)

Called when the focus state of a virtual view changes.