Add View.findOnBackInvokedDispatcher

To make it easier for developer to migrate away from KEYCODE_BACK
without having to walk up the view hierachy in order to find an
OnBackDispatcher, introduce findOnBackInvokedDispatcher.

Bug: 227301455
Test: android.view.cts.OnBackInvokedDispatcherTest#testGetDispatcherOnView
Change-Id: I7f3e76df596d306fa26d72df8115d5b15d7ac564

core/api/current.txt

@@ -49642,6 +49642,7 @@ package android.view {
     method @CallSuper public void drawableHotspotChanged(float, float);
     method @CallSuper protected void drawableStateChanged();
     method public android.view.View findFocus();
+    method @Nullable public final android.window.OnBackInvokedDispatcher findOnBackInvokedDispatcher();
     method public final <T extends android.view.View> T findViewById(@IdRes int);
     method public final <T extends android.view.View> T findViewWithTag(Object);
     method public void findViewsWithText(java.util.ArrayList<android.view.View>, CharSequence, int);
@@ -50819,6 +50820,7 @@ package android.view {
     method public void childHasTransientStateChanged(@NonNull android.view.View, boolean);
     method public void clearChildFocus(android.view.View);
     method public void createContextMenu(android.view.ContextMenu);
+    method @Nullable public default android.window.OnBackInvokedDispatcher findOnBackInvokedDispatcherForChild(@NonNull android.view.View, @NonNull android.view.View);
     method public android.view.View focusSearch(android.view.View, int);
     method public void focusableViewAvailable(android.view.View);
     method public boolean getChildVisibleRect(android.view.View, android.graphics.Rect, android.graphics.Point);

core/java/android/view/View.java

@@ -162,6 +162,7 @@ import android.view.translation.ViewTranslationResponse;
 import android.widget.Checkable;
 import android.widget.FrameLayout;
 import android.widget.ScrollBarDrawable;
+import android.window.OnBackInvokedDispatcher;
 
 import com.android.internal.R;
 import com.android.internal.util.ArrayUtils;
@@ -12098,6 +12099,23 @@ public class View implements Drawable.Callback, KeyEvent.Callback,
         return null;
     }
 
+
+    /**
+     * Walk up the View hierarchy to find the nearest {@link OnBackInvokedDispatcher}.
+     *
+     * @return The {@link OnBackInvokedDispatcher} from this or the nearest
+     * ancestor, or null if this view is both not attached and have no ancestor providing an
+     * {@link OnBackInvokedDispatcher}.
+     */
+    @Nullable
+    public final OnBackInvokedDispatcher findOnBackInvokedDispatcher() {
+        ViewParent parent = getParent();
+        if (parent != null) {
+            return parent.findOnBackInvokedDispatcherForChild(this, this);
+        }
+        return null;
+    }
+
     /**
      * @hide Compute the insets that should be consumed by this view and the ones
      * that should propagate to those under it.

core/java/android/view/ViewGroup.java

@@ -72,6 +72,7 @@ import android.view.inspector.InspectableProperty.EnumEntry;
 import android.view.translation.TranslationCapability;
 import android.view.translation.TranslationSpec.DataFormat;
 import android.view.translation.ViewTranslationRequest;
+import android.window.OnBackInvokedDispatcher;
 
 import com.android.internal.R;
 
@@ -9296,4 +9297,25 @@ public abstract class ViewGroup extends View implements ViewParent, ViewManager
                     requests);
         }
     }
+
+    /**
+     * Walk up the View hierarchy to find the nearest {@link OnBackInvokedDispatcher}.
+     *
+     * @return The {@link OnBackInvokedDispatcher} from this or the nearest
+     * ancestor, or null if the view is both not attached and have no ancestor providing an
+     * {@link OnBackInvokedDispatcher}.
+     *
+     * @param child The direct child of this view for which to find a dispatcher.
+     * @param requester The requester that will use the dispatcher. Can be the same as child.
+     */
+    @Nullable
+    @Override
+    public OnBackInvokedDispatcher findOnBackInvokedDispatcherForChild(@NonNull View child,
+            @NonNull View requester) {
+        ViewParent parent = getParent();
+        if (parent != null) {
+            return parent.findOnBackInvokedDispatcherForChild(this, requester);
+        }
+        return null;
+    }
 }

core/java/android/view/ViewParent.java

@@ -22,6 +22,7 @@ import android.graphics.Rect;
 import android.graphics.Region;
 import android.os.Bundle;
 import android.view.accessibility.AccessibilityEvent;
+import android.window.OnBackInvokedDispatcher;
 
 /**
  * Defines the responsibilities for a class that will be a parent of a View.
@@ -697,4 +698,20 @@ public interface ViewParent {
             getParent().onDescendantUnbufferedRequested();
         }
     }
+
+    /**
+     * Walk up the View hierarchy to find the nearest {@link OnBackInvokedDispatcher}.
+     *
+     * @return The {@link OnBackInvokedDispatcher} from this or the nearest
+     * ancestor, or null if the view is both not attached and have no ancestor providing an
+     * {@link OnBackInvokedDispatcher}.
+     *
+     * @param child The direct child of this view for which to find a dispatcher.
+     * @param requester The requester that will use the dispatcher. Can be the same as child.
+     */
+    @Nullable
+    default OnBackInvokedDispatcher findOnBackInvokedDispatcherForChild(@NonNull View child,
+            @NonNull View requester) {
+        return null;
+    }
 }

core/java/android/view/ViewRootImpl.java

@@ -10736,6 +10736,13 @@ public final class ViewRootImpl implements ViewParent,
         return mOnBackInvokedDispatcher;
     }
 
+    @NonNull
+    @Override
+    public OnBackInvokedDispatcher findOnBackInvokedDispatcherForChild(
+            @NonNull View child, @NonNull View requester) {
+        return getOnBackInvokedDispatcher();
+    }
+
     /**
      * When this ViewRootImpl is added to the window manager, transfers the first
      * {@link OnBackInvokedCallback} to be called to the server.