Make OnBackAnimationCallback and BackEvent public.

Bug: 238475284
Test: BackNavigationGestureTest
Test: BackAnimationControllerTest
Change-Id: Ib342a92add166d804336653ab868bc0349540b2c
diff --git a/boot/preloaded-classes b/boot/preloaded-classes
index d8b348e..528ce86 100644
--- a/boot/preloaded-classes
+++ b/boot/preloaded-classes
@@ -9358,8 +9358,8 @@
 android.widget.inline.InlinePresentationSpec$BaseBuilder
 android.widget.inline.InlinePresentationSpec$Builder
 android.widget.inline.InlinePresentationSpec
-android.window.BackEvent$1
-android.window.BackEvent
+android.window.BackMotionEvent$1
+android.window.BackMotionEvent
 android.window.ClientWindowFrames$1
 android.window.ClientWindowFrames
 android.window.CompatOnBackInvokedCallback
diff --git a/config/preloaded-classes b/config/preloaded-classes
index f750249..fa60140 100644
--- a/config/preloaded-classes
+++ b/config/preloaded-classes
@@ -9389,8 +9389,8 @@
 android.widget.inline.InlinePresentationSpec$BaseBuilder
 android.widget.inline.InlinePresentationSpec$Builder
 android.widget.inline.InlinePresentationSpec
-android.window.BackEvent$1
-android.window.BackEvent
+android.window.BackMotionEvent$1
+android.window.BackMotionEvent
 android.window.ClientWindowFrames$1
 android.window.ClientWindowFrames
 android.window.CompatOnBackInvokedCallback
diff --git a/core/api/current.txt b/core/api/current.txt
index 5f87537..64f7fcb 100644
--- a/core/api/current.txt
+++ b/core/api/current.txt
@@ -59112,6 +59112,22 @@
 
 package android.window {
 
+  public final class BackEvent {
+    ctor public BackEvent(float, float, float, int);
+    method @FloatRange(from=0, to=1) public float getProgress();
+    method public int getSwipeEdge();
+    method public float getTouchX();
+    method public float getTouchY();
+    field public static final int EDGE_LEFT = 0; // 0x0
+    field public static final int EDGE_RIGHT = 1; // 0x1
+  }
+
+  public interface OnBackAnimationCallback extends android.window.OnBackInvokedCallback {
+    method public default void onBackCancelled();
+    method public default void onBackProgressed(@NonNull android.window.BackEvent);
+    method public default void onBackStarted(@NonNull android.window.BackEvent);
+  }
+
   public interface OnBackInvokedCallback {
     method public void onBackInvoked();
   }
diff --git a/core/java/android/window/BackEvent.java b/core/java/android/window/BackEvent.java
index 85b2881..40c0fee 100644
--- a/core/java/android/window/BackEvent.java
+++ b/core/java/android/window/BackEvent.java
@@ -16,29 +16,24 @@
 
 package android.window;
 
+import android.annotation.FloatRange;
 import android.annotation.IntDef;
-import android.annotation.NonNull;
-import android.annotation.Nullable;
-import android.os.Parcel;
-import android.os.Parcelable;
-import android.view.RemoteAnimationTarget;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 
 /**
- * Represents an event that is sent out by the system during back navigation gesture.
- * Holds information about the touch event, swipe direction and overall progress of the gesture
- * interaction.
- *
- * @hide
+ * Object used to report back gesture progress.
+ * Holds information about the touch event, swipe direction and the animation progress that
+ * predictive back animations should seek to.
  */
-public class BackEvent implements Parcelable {
+public final class BackEvent {
     /** Indicates that the edge swipe starts from the left edge of the screen */
     public static final int EDGE_LEFT = 0;
     /** Indicates that the edge swipe starts from the right edge of the screen */
     public static final int EDGE_RIGHT = 1;
 
+    /** @hide */
     @IntDef({
             EDGE_LEFT,
             EDGE_RIGHT,
@@ -52,78 +47,52 @@
 
     @SwipeEdge
     private final int mSwipeEdge;
-    @Nullable
-    private final RemoteAnimationTarget mDepartingAnimationTarget;
 
     /**
-     * Creates a new {@link BackEvent} instance.
+     * Creates a new {@link BackMotionEvent} instance.
      *
      * @param touchX Absolute X location of the touch point of this event.
      * @param touchY Absolute Y location of the touch point of this event.
      * @param progress Value between 0 and 1 on how far along the back gesture is.
      * @param swipeEdge Indicates which edge the swipe starts from.
-     * @param departingAnimationTarget The remote animation target of the departing
-     *                                 application window.
      */
-    public BackEvent(float touchX, float touchY, float progress, @SwipeEdge int swipeEdge,
-            @Nullable RemoteAnimationTarget departingAnimationTarget) {
+    public BackEvent(float touchX, float touchY, float progress, @SwipeEdge int swipeEdge) {
         mTouchX = touchX;
         mTouchY = touchY;
         mProgress = progress;
         mSwipeEdge = swipeEdge;
-        mDepartingAnimationTarget = departingAnimationTarget;
-    }
-
-    private BackEvent(@NonNull Parcel in) {
-        mTouchX = in.readFloat();
-        mTouchY = in.readFloat();
-        mProgress = in.readFloat();
-        mSwipeEdge = in.readInt();
-        mDepartingAnimationTarget = in.readTypedObject(RemoteAnimationTarget.CREATOR);
-    }
-
-    public static final Creator<BackEvent> CREATOR = new Creator<BackEvent>() {
-        @Override
-        public BackEvent createFromParcel(Parcel in) {
-            return new BackEvent(in);
-        }
-
-        @Override
-        public BackEvent[] newArray(int size) {
-            return new BackEvent[size];
-        }
-    };
-
-    @Override
-    public int describeContents() {
-        return 0;
-    }
-
-    @Override
-    public void writeToParcel(@NonNull Parcel dest, int flags) {
-        dest.writeFloat(mTouchX);
-        dest.writeFloat(mTouchY);
-        dest.writeFloat(mProgress);
-        dest.writeInt(mSwipeEdge);
-        dest.writeTypedObject(mDepartingAnimationTarget, flags);
     }
 
     /**
-     * Returns a value between 0 and 1 on how far along the back gesture is.
+     * Returns a value between 0 and 1 on how far along the back gesture is. This value is
+     * driven by the horizontal location of the touch point, and should be used as the fraction to
+     * seek the predictive back animation with. Specifically,
+     * <ol>
+     * <li>The progress is 0 when the touch is at the starting edge of the screen (left or right),
+     * and animation should seek to its start state.
+     * <li>The progress is approximately 1 when the touch is at the opposite side of the screen,
+     * and animation should seek to its end state. Exact end value may vary depending on
+     * screen size.
+     * </ol>
+     * In-between locations are linearly interpolated based on horizontal distance from the starting
+     * edge and smooth clamped to 1 when the distance exceeds a system-wide threshold.
      */
+    @FloatRange(from = 0, to = 1)
     public float getProgress() {
         return mProgress;
     }
 
     /**
-     * Returns the absolute X location of the touch point.
+     * Returns the absolute X location of the touch point, or NaN if the event is from
+     * a button press.
      */
     public float getTouchX() {
         return mTouchX;
     }
 
     /**
-     * Returns the absolute Y location of the touch point.
+     * Returns the absolute Y location of the touch point, or NaN if the event is from
+     * a button press.
      */
     public float getTouchY() {
         return mTouchY;
@@ -132,20 +101,11 @@
     /**
      * Returns the screen edge that the swipe starts from.
      */
+    @SwipeEdge
     public int getSwipeEdge() {
         return mSwipeEdge;
     }
 
-    /**
-     * Returns the {@link RemoteAnimationTarget} of the top departing application window,
-     * or {@code null} if the top window should not be moved for the current type of back
-     * destination.
-     */
-    @Nullable
-    public RemoteAnimationTarget getDepartingAnimationTarget() {
-        return mDepartingAnimationTarget;
-    }
-
     @Override
     public String toString() {
         return "BackEvent{"
diff --git a/core/java/android/window/BackEvent.aidl b/core/java/android/window/BackMotionEvent.aidl
similarity index 95%
rename from core/java/android/window/BackEvent.aidl
rename to core/java/android/window/BackMotionEvent.aidl
index 821f1fa..7c675c3 100644
--- a/core/java/android/window/BackEvent.aidl
+++ b/core/java/android/window/BackMotionEvent.aidl
@@ -19,4 +19,4 @@
 /**
  * @hide
  */
-parcelable BackEvent;
+parcelable BackMotionEvent;
diff --git a/core/java/android/window/BackMotionEvent.java b/core/java/android/window/BackMotionEvent.java
new file mode 100644
index 0000000..8012a1c
--- /dev/null
+++ b/core/java/android/window/BackMotionEvent.java
@@ -0,0 +1,150 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.window;
+
+import android.annotation.FloatRange;
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.os.Parcel;
+import android.os.Parcelable;
+import android.view.RemoteAnimationTarget;
+
+/**
+ * Object used to report back gesture progress. Holds information about a {@link BackEvent} plus
+ * any {@link RemoteAnimationTarget} the gesture manipulates.
+ *
+ * @see BackEvent
+ * @hide
+ */
+public final class BackMotionEvent implements Parcelable {
+    private final float mTouchX;
+    private final float mTouchY;
+    private final float mProgress;
+
+    @BackEvent.SwipeEdge
+    private final int mSwipeEdge;
+    @Nullable
+    private final RemoteAnimationTarget mDepartingAnimationTarget;
+
+    /**
+     * Creates a new {@link BackMotionEvent} instance.
+     *
+     * @param touchX Absolute X location of the touch point of this event.
+     * @param touchY Absolute Y location of the touch point of this event.
+     * @param progress Value between 0 and 1 on how far along the back gesture is.
+     * @param swipeEdge Indicates which edge the swipe starts from.
+     * @param departingAnimationTarget The remote animation target of the departing
+     *                                 application window.
+     */
+    public BackMotionEvent(float touchX, float touchY, float progress,
+            @BackEvent.SwipeEdge int swipeEdge,
+            @Nullable RemoteAnimationTarget departingAnimationTarget) {
+        mTouchX = touchX;
+        mTouchY = touchY;
+        mProgress = progress;
+        mSwipeEdge = swipeEdge;
+        mDepartingAnimationTarget = departingAnimationTarget;
+    }
+
+    private BackMotionEvent(@NonNull Parcel in) {
+        mTouchX = in.readFloat();
+        mTouchY = in.readFloat();
+        mProgress = in.readFloat();
+        mSwipeEdge = in.readInt();
+        mDepartingAnimationTarget = in.readTypedObject(RemoteAnimationTarget.CREATOR);
+    }
+
+    @NonNull
+    public static final Creator<BackMotionEvent> CREATOR = new Creator<BackMotionEvent>() {
+        @Override
+        public BackMotionEvent createFromParcel(Parcel in) {
+            return new BackMotionEvent(in);
+        }
+
+        @Override
+        public BackMotionEvent[] newArray(int size) {
+            return new BackMotionEvent[size];
+        }
+    };
+
+    @Override
+    public int describeContents() {
+        return 0;
+    }
+
+    @Override
+    public void writeToParcel(@NonNull Parcel dest, int flags) {
+        dest.writeFloat(mTouchX);
+        dest.writeFloat(mTouchY);
+        dest.writeFloat(mProgress);
+        dest.writeInt(mSwipeEdge);
+        dest.writeTypedObject(mDepartingAnimationTarget, flags);
+    }
+
+    /**
+     * Returns the progress of a {@link BackEvent}.
+     *
+     * @see BackEvent#getProgress()
+     */
+    @FloatRange(from = 0, to = 1)
+    public float getProgress() {
+        return mProgress;
+    }
+
+    /**
+     * Returns the absolute X location of the touch point.
+     */
+    public float getTouchX() {
+        return mTouchX;
+    }
+
+    /**
+     * Returns the absolute Y location of the touch point.
+     */
+    public float getTouchY() {
+        return mTouchY;
+    }
+
+    /**
+     * Returns the screen edge that the swipe starts from.
+     */
+    @BackEvent.SwipeEdge
+    public int getSwipeEdge() {
+        return mSwipeEdge;
+    }
+
+    /**
+     * Returns the {@link RemoteAnimationTarget} of the top departing application window,
+     * or {@code null} if the top window should not be moved for the current type of back
+     * destination.
+     */
+    @Nullable
+    public RemoteAnimationTarget getDepartingAnimationTarget() {
+        return mDepartingAnimationTarget;
+    }
+
+    @Override
+    public String toString() {
+        return "BackMotionEvent{"
+                + "mTouchX=" + mTouchX
+                + ", mTouchY=" + mTouchY
+                + ", mProgress=" + mProgress
+                + ", mSwipeEdge" + mSwipeEdge
+                + ", mDepartingAnimationTarget" + mDepartingAnimationTarget
+                + "}";
+    }
+}
diff --git a/core/java/android/window/BackProgressAnimator.java b/core/java/android/window/BackProgressAnimator.java
index 2e3afde..14a57e0 100644
--- a/core/java/android/window/BackProgressAnimator.java
+++ b/core/java/android/window/BackProgressAnimator.java
@@ -40,7 +40,7 @@
     private final SpringAnimation mSpring;
     private ProgressCallback mCallback;
     private float mProgress = 0;
-    private BackEvent mLastBackEvent;
+    private BackMotionEvent mLastBackEvent;
     private boolean mStarted = false;
 
     private void setProgress(float progress) {
@@ -82,9 +82,9 @@
     /**
      * Sets a new target position for the back progress.
      *
-     * @param event the {@link BackEvent} containing the latest target progress.
+     * @param event the {@link BackMotionEvent} containing the latest target progress.
      */
-    public void onBackProgressed(BackEvent event) {
+    public void onBackProgressed(BackMotionEvent event) {
         if (!mStarted) {
             return;
         }
@@ -98,11 +98,11 @@
     /**
      * Starts the back progress animation.
      *
-     * @param event the {@link BackEvent} that started the gesture.
+     * @param event the {@link BackMotionEvent} that started the gesture.
      * @param callback the back callback to invoke for the gesture. It will receive back progress
      *                 dispatches as the progress animation updates.
      */
-    public void onBackStarted(BackEvent event, ProgressCallback callback) {
+    public void onBackStarted(BackMotionEvent event, ProgressCallback callback) {
         reset();
         mLastBackEvent = event;
         mCallback = callback;
@@ -132,8 +132,7 @@
         }
         mCallback.onProgressUpdate(
                 new BackEvent(mLastBackEvent.getTouchX(), mLastBackEvent.getTouchY(),
-                        progress / SCALE_FACTOR, mLastBackEvent.getSwipeEdge(),
-                        mLastBackEvent.getDepartingAnimationTarget()));
+                        progress / SCALE_FACTOR, mLastBackEvent.getSwipeEdge()));
     }
 
 }
diff --git a/core/java/android/window/IOnBackInvokedCallback.aidl b/core/java/android/window/IOnBackInvokedCallback.aidl
index 6af8ddd..159c0e8 100644
--- a/core/java/android/window/IOnBackInvokedCallback.aidl
+++ b/core/java/android/window/IOnBackInvokedCallback.aidl
@@ -17,7 +17,7 @@
 
 package android.window;
 
-import android.window.BackEvent;
+import android.window.BackMotionEvent;
 
 /**
  * Interface that wraps a {@link OnBackInvokedCallback} object, to be stored in window manager
@@ -30,18 +30,19 @@
     * Called when a back gesture has been started, or back button has been pressed down.
     * Wraps {@link OnBackInvokedCallback#onBackStarted(BackEvent)}.
     *
-    * @param backEvent The {@link BackEvent} containing information about the touch or button press.
+    * @param backMotionEvent The {@link BackMotionEvent} containing information about the touch
+    *        or button press.
     */
-    void onBackStarted(in BackEvent backEvent);
+    void onBackStarted(in BackMotionEvent backMotionEvent);
 
     /**
      * Called on back gesture progress.
      * Wraps {@link OnBackInvokedCallback#onBackProgressed(BackEvent)}.
      *
-     * @param backEvent The {@link BackEvent} containing information about the latest touch point
-     *                  and the progress that the back animation should seek to.
+     * @param backMotionEvent The {@link BackMotionEvent} containing information about the latest
+     *                        touch point and the progress that the back animation should seek to.
      */
-    void onBackProgressed(in BackEvent backEvent);
+    void onBackProgressed(in BackMotionEvent backMotionEvent);
 
     /**
      * Called when a back gesture or back button press has been cancelled.
diff --git a/core/java/android/window/OnBackAnimationCallback.java b/core/java/android/window/OnBackAnimationCallback.java
index c05809b..9119e71 100644
--- a/core/java/android/window/OnBackAnimationCallback.java
+++ b/core/java/android/window/OnBackAnimationCallback.java
@@ -18,6 +18,8 @@
 import android.app.Activity;
 import android.app.Dialog;
 import android.view.View;
+import android.view.Window;
+
 /**
  * Interface for applications to register back animation callbacks along their custom back
  * handling.
@@ -25,24 +27,29 @@
  * This allows the client to customize various back behaviors by overriding the corresponding
  * callback methods.
  * <p>
- * Callback instances can be added to and removed from {@link OnBackInvokedDispatcher}, held
- * by classes that implement {@link OnBackInvokedDispatcherOwner} (such as {@link Activity},
- * {@link Dialog} and {@link View}).
+ * Callback instances can be added to and removed from {@link OnBackInvokedDispatcher}, which
+ * is held at window level and accessible through {@link Activity#getOnBackInvokedDispatcher()},
+ * {@link Dialog#getOnBackInvokedDispatcher()}, {@link Window#getOnBackInvokedDispatcher()}
+ * and {@link View#findOnBackInvokedDispatcher()}.
  * <p>
  * When back is triggered, callbacks on the in-focus window are invoked in reverse order in which
  * they are added within the same priority. Between different priorities, callbacks with higher
  * priority are invoked first.
  * <p>
  * @see OnBackInvokedCallback
- * @hide
  */
 public interface OnBackAnimationCallback extends OnBackInvokedCallback {
     /**
      * Called when a back gesture has been started, or back button has been pressed down.
+     *
+     * @param backEvent The {@link BackEvent} containing information about the touch or
+     *                  button press.
+     * @see BackEvent
      */
-    default void onBackStarted() { }
+    default void onBackStarted(@NonNull BackEvent backEvent) {}
+
     /**
-     * Called on back gesture progress.
+     * Called when a back gesture progresses.
      *
      * @param backEvent An {@link BackEvent} object describing the progress event.
      *
diff --git a/core/java/android/window/OnBackInvokedCallback.java b/core/java/android/window/OnBackInvokedCallback.java
index 62c41bf..6beaad3 100644
--- a/core/java/android/window/OnBackInvokedCallback.java
+++ b/core/java/android/window/OnBackInvokedCallback.java
@@ -16,9 +16,9 @@
 
 package android.window;
 
-import android.annotation.NonNull;
 import android.app.Activity;
 import android.app.Dialog;
+import android.view.View;
 import android.view.Window;
 
 /**
@@ -26,7 +26,8 @@
  * <p>
  * Callback instances can be added to and removed from {@link OnBackInvokedDispatcher}, which
  * is held at window level and accessible through {@link Activity#getOnBackInvokedDispatcher()},
- * {@link Dialog#getOnBackInvokedDispatcher()} and {@link Window#getOnBackInvokedDispatcher()}.
+ * {@link Dialog#getOnBackInvokedDispatcher()}, {@link Window#getOnBackInvokedDispatcher()}
+ * and {@link View#findOnBackInvokedDispatcher()}.
  * <p>
  * When back is triggered, callbacks on the in-focus window are invoked in reverse order in which
  * they are added within the same priority. Between different priorities, callbacks with higher
@@ -35,6 +36,9 @@
  * This replaces {@link Activity#onBackPressed()}, {@link Dialog#onBackPressed()} and
  * {@link android.view.KeyEvent#KEYCODE_BACK}
  * <p>
+ * If you want to customize back animation behaviors, in addition to handling back invocations,
+ * register its subclass instances {@link OnBackAnimationCallback} instead.
+ * <p>
  * @see OnBackInvokedDispatcher#registerOnBackInvokedCallback(int, OnBackInvokedCallback)
  * registerOnBackInvokedCallback(priority, OnBackInvokedCallback)
  * to specify callback priority.
@@ -42,35 +46,8 @@
 @SuppressWarnings("deprecation")
 public interface OnBackInvokedCallback {
     /**
-     * Called when a back gesture has been started, or back button has been pressed down.
-     *
-     * @param backEvent The {@link BackEvent} containing information about the touch or
-     *                  button press.
-     *
-     * @hide
-     */
-    default void onBackStarted(@NonNull BackEvent backEvent) {}
-
-    /**
-     * Called when a back gesture has been progressed.
-     *
-     * @param backEvent The {@link BackEvent} containing information about the latest touch point
-     *                  and the progress that the back animation should seek to.
-     *
-     * @hide
-     */
-    default void onBackProgressed(@NonNull BackEvent backEvent) {}
-
-    /**
      * Called when a back gesture has been completed and committed, or back button pressed
      * has been released and committed.
      */
     void onBackInvoked();
-
-    /**
-     * Called when a back gesture or button press has been cancelled.
-     *
-     * @hide
-     */
-    default void onBackCancelled() {}
 }
diff --git a/core/java/android/window/WindowOnBackInvokedDispatcher.java b/core/java/android/window/WindowOnBackInvokedDispatcher.java
index fda39c1..dd9483a 100644
--- a/core/java/android/window/WindowOnBackInvokedDispatcher.java
+++ b/core/java/android/window/WindowOnBackInvokedDispatcher.java
@@ -229,19 +229,21 @@
         }
 
         @Override
-        public void onBackStarted(BackEvent backEvent) {
+        public void onBackStarted(BackMotionEvent backEvent) {
             Handler.getMain().post(() -> {
                 final OnBackAnimationCallback callback = getBackAnimationCallback();
                 if (callback != null) {
                     mProgressAnimator.onBackStarted(backEvent, event ->
                             callback.onBackProgressed(event));
-                    callback.onBackStarted(backEvent);
+                    callback.onBackStarted(new BackEvent(
+                            backEvent.getTouchX(), backEvent.getTouchY(),
+                            backEvent.getProgress(), backEvent.getSwipeEdge()));
                 }
             });
         }
 
         @Override
-        public void onBackProgressed(BackEvent backEvent) {
+        public void onBackProgressed(BackMotionEvent backEvent) {
             Handler.getMain().post(() -> {
                 final OnBackAnimationCallback callback = getBackAnimationCallback();
                 if (callback != null) {
diff --git a/core/tests/coretests/src/android/window/WindowOnBackInvokedDispatcherTest.java b/core/tests/coretests/src/android/window/WindowOnBackInvokedDispatcherTest.java
index f370ebd..9d6b29e 100644
--- a/core/tests/coretests/src/android/window/WindowOnBackInvokedDispatcherTest.java
+++ b/core/tests/coretests/src/android/window/WindowOnBackInvokedDispatcherTest.java
@@ -17,6 +17,7 @@
 package android.window;
 
 import static org.junit.Assert.assertEquals;
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.isNull;
 import static org.mockito.Mockito.reset;
 import static org.mockito.Mockito.times;
@@ -60,8 +61,8 @@
     private OnBackAnimationCallback mCallback1;
     @Mock
     private OnBackAnimationCallback mCallback2;
-    @Mock
-    private BackEvent mBackEvent;
+    private final BackMotionEvent mBackEvent = new BackMotionEvent(
+            0, 0, 0, BackEvent.EDGE_LEFT, null);
 
     @Before
     public void setUp() throws Exception {
@@ -89,12 +90,12 @@
                 captor.capture());
         captor.getAllValues().get(0).getCallback().onBackStarted(mBackEvent);
         waitForIdle();
-        verify(mCallback1).onBackStarted(mBackEvent);
+        verify(mCallback1).onBackStarted(any(BackEvent.class));
         verifyZeroInteractions(mCallback2);
 
         captor.getAllValues().get(1).getCallback().onBackStarted(mBackEvent);
         waitForIdle();
-        verify(mCallback2).onBackStarted(mBackEvent);
+        verify(mCallback2).onBackStarted(any(BackEvent.class));
         verifyNoMoreInteractions(mCallback1);
     }
 
@@ -114,7 +115,7 @@
         assertEquals(captor.getValue().getPriority(), OnBackInvokedDispatcher.PRIORITY_OVERLAY);
         captor.getValue().getCallback().onBackStarted(mBackEvent);
         waitForIdle();
-        verify(mCallback1).onBackStarted(mBackEvent);
+        verify(mCallback1).onBackStarted(any(BackEvent.class));
     }
 
     @Test
@@ -152,6 +153,6 @@
         verify(mWindowSession).setOnBackInvokedCallbackInfo(Mockito.eq(mWindow), captor.capture());
         captor.getValue().getCallback().onBackStarted(mBackEvent);
         waitForIdle();
-        verify(mCallback2).onBackStarted(mBackEvent);
+        verify(mCallback2).onBackStarted(any(BackEvent.class));
     }
 }
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java b/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java
index 0133f6b..57a0fd5 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/back/BackAnimationController.java
@@ -47,6 +47,7 @@
 import android.view.RemoteAnimationTarget;
 import android.window.BackAnimationAdapter;
 import android.window.BackEvent;
+import android.window.BackMotionEvent;
 import android.window.BackNavigationInfo;
 import android.window.IBackAnimationFinishedCallback;
 import android.window.IBackAnimationRunner;
@@ -385,7 +386,7 @@
             return;
         }
 
-        final BackEvent backEvent = mTouchTracker.createProgressEvent();
+        final BackMotionEvent backEvent = mTouchTracker.createProgressEvent();
         dispatchOnBackProgressed(mActiveCallback, backEvent);
     }
 
@@ -415,7 +416,7 @@
     }
 
     private void dispatchOnBackStarted(IOnBackInvokedCallback callback,
-            BackEvent backEvent) {
+            BackMotionEvent backEvent) {
         if (callback == null) {
             return;
         }
@@ -453,7 +454,7 @@
     }
 
     private void dispatchOnBackProgressed(IOnBackInvokedCallback callback,
-            BackEvent backEvent) {
+            BackMotionEvent backEvent) {
         if (callback == null) {
             return;
         }
@@ -466,6 +467,11 @@
         }
     }
 
+    private boolean shouldDispatchAnimation(IOnBackInvokedCallback callback) {
+        // TODO(b/258698745): Only dispatch to animation callbacks.
+        return mEnableAnimations.get();
+    }
+
     /**
      * Sets to true when the back gesture has passed the triggering threshold, false otherwise.
      */
@@ -640,7 +646,7 @@
                     if (!mBackGestureStarted) {
                         // if the down -> up gesture happened before animation start, we have to
                         // trigger the uninterruptible transition to finish the back animation.
-                        final BackEvent backFinish = mTouchTracker.createProgressEvent();
+                        final BackMotionEvent backFinish = mTouchTracker.createProgressEvent();
                         dispatchOnBackProgressed(mActiveCallback, backFinish);
                         startPostCommitAnimation();
                     }
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/back/CrossActivityAnimation.java b/libs/WindowManager/Shell/src/com/android/wm/shell/back/CrossActivityAnimation.java
index 9f6bc5d..e36e16c 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/back/CrossActivityAnimation.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/back/CrossActivityAnimation.java
@@ -39,6 +39,7 @@
 import android.view.animation.DecelerateInterpolator;
 import android.view.animation.Interpolator;
 import android.window.BackEvent;
+import android.window.BackMotionEvent;
 import android.window.BackProgressAnimator;
 import android.window.IOnBackInvokedCallback;
 
@@ -315,13 +316,13 @@
 
     private final class Callback extends IOnBackInvokedCallback.Default {
         @Override
-        public void onBackStarted(BackEvent backEvent) {
+        public void onBackStarted(BackMotionEvent backEvent) {
             mProgressAnimator.onBackStarted(backEvent,
                     CrossActivityAnimation.this::onGestureProgress);
         }
 
         @Override
-        public void onBackProgressed(@NonNull BackEvent backEvent) {
+        public void onBackProgressed(@NonNull BackMotionEvent backEvent) {
             mProgressAnimator.onBackProgressed(backEvent);
         }
 
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/back/CrossTaskBackAnimation.java b/libs/WindowManager/Shell/src/com/android/wm/shell/back/CrossTaskBackAnimation.java
index a9a7b77..676e259 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/back/CrossTaskBackAnimation.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/back/CrossTaskBackAnimation.java
@@ -39,6 +39,7 @@
 import android.view.animation.AccelerateDecelerateInterpolator;
 import android.view.animation.Interpolator;
 import android.window.BackEvent;
+import android.window.BackMotionEvent;
 import android.window.BackProgressAnimator;
 import android.window.IOnBackInvokedCallback;
 
@@ -316,13 +317,13 @@
 
     private final class Callback extends IOnBackInvokedCallback.Default  {
         @Override
-        public void onBackStarted(BackEvent backEvent) {
+        public void onBackStarted(BackMotionEvent backEvent) {
             mProgressAnimator.onBackStarted(backEvent,
                     CrossTaskBackAnimation.this::onGestureProgress);
         }
 
         @Override
-        public void onBackProgressed(@NonNull BackEvent backEvent) {
+        public void onBackProgressed(@NonNull BackMotionEvent backEvent) {
             mProgressAnimator.onBackProgressed(backEvent);
         }
 
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/back/TouchTracker.java b/libs/WindowManager/Shell/src/com/android/wm/shell/back/TouchTracker.java
index ccfac65..695ef4e 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/back/TouchTracker.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/back/TouchTracker.java
@@ -19,6 +19,7 @@
 import android.os.SystemProperties;
 import android.view.RemoteAnimationTarget;
 import android.window.BackEvent;
+import android.window.BackMotionEvent;
 
 /**
  * Helper class to record the touch location for gesture and generate back events.
@@ -82,11 +83,11 @@
         mSwipeEdge = BackEvent.EDGE_LEFT;
     }
 
-    BackEvent createStartEvent(RemoteAnimationTarget target) {
-        return new BackEvent(mInitTouchX, mInitTouchY, 0, mSwipeEdge, target);
+    BackMotionEvent createStartEvent(RemoteAnimationTarget target) {
+        return new BackMotionEvent(mInitTouchX, mInitTouchY, 0, mSwipeEdge, target);
     }
 
-    BackEvent createProgressEvent() {
+    BackMotionEvent createProgressEvent() {
         float progressThreshold = PROGRESS_THRESHOLD >= 0
                 ? PROGRESS_THRESHOLD : mProgressThreshold;
         progressThreshold = progressThreshold == 0 ? 1 : progressThreshold;
@@ -109,8 +110,8 @@
         return createProgressEvent(progress);
     }
 
-    BackEvent createProgressEvent(float progress) {
-        return new BackEvent(mLatestTouchX, mLatestTouchY, progress, mSwipeEdge, null);
+    BackMotionEvent createProgressEvent(float progress) {
+        return new BackMotionEvent(mLatestTouchX, mLatestTouchY, progress, mSwipeEdge, null);
     }
 
     public void setProgressThreshold(float progressThreshold) {
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/BackAnimationControllerTest.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/BackAnimationControllerTest.java
index bee9a90..8a5b490 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/BackAnimationControllerTest.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/BackAnimationControllerTest.java
@@ -53,6 +53,7 @@
 import android.view.RemoteAnimationTarget;
 import android.view.SurfaceControl;
 import android.window.BackEvent;
+import android.window.BackMotionEvent;
 import android.window.BackNavigationInfo;
 import android.window.IBackAnimationFinishedCallback;
 import android.window.IOnBackInvokedCallback;
@@ -223,9 +224,10 @@
 
         simulateRemoteAnimationStart(BackNavigationInfo.TYPE_RETURN_TO_HOME);
 
-        verify(mAnimatorCallback).onBackStarted(any(BackEvent.class));
+        verify(mAnimatorCallback).onBackStarted(any(BackMotionEvent.class));
         verify(mBackAnimationRunner).onAnimationStart(anyInt(), any(), any(), any(), any());
-        ArgumentCaptor<BackEvent> backEventCaptor = ArgumentCaptor.forClass(BackEvent.class);
+        ArgumentCaptor<BackMotionEvent> backEventCaptor =
+                ArgumentCaptor.forClass(BackMotionEvent.class);
         verify(mAnimatorCallback, atLeastOnce()).onBackProgressed(backEventCaptor.capture());
 
         // Check that back invocation is dispatched.
@@ -246,7 +248,8 @@
         shellInit.init();
         registerAnimation(BackNavigationInfo.TYPE_RETURN_TO_HOME);
 
-        ArgumentCaptor<BackEvent> backEventCaptor = ArgumentCaptor.forClass(BackEvent.class);
+        ArgumentCaptor<BackMotionEvent> backEventCaptor =
+                ArgumentCaptor.forClass(BackMotionEvent.class);
 
         createNavigationInfo(BackNavigationInfo.TYPE_RETURN_TO_HOME, false);
 
diff --git a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/TouchTrackerTest.java b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/TouchTrackerTest.java
index 3aefc3f..ba9c159 100644
--- a/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/TouchTrackerTest.java
+++ b/libs/WindowManager/Shell/tests/unittest/src/com/android/wm/shell/back/TouchTrackerTest.java
@@ -19,6 +19,7 @@
 import static org.junit.Assert.assertEquals;
 
 import android.window.BackEvent;
+import android.window.BackMotionEvent;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -38,7 +39,7 @@
     @Test
     public void generatesProgress_onStart() {
         mTouchTracker.setGestureStartLocation(INITIAL_X_LEFT_EDGE, 0, BackEvent.EDGE_LEFT);
-        BackEvent event = mTouchTracker.createStartEvent(null);
+        BackMotionEvent event = mTouchTracker.createStartEvent(null);
         assertEquals(event.getProgress(), 0f, 0f);
     }
 
diff --git a/services/tests/wmtests/src/com/android/server/wm/BackNavigationControllerTests.java b/services/tests/wmtests/src/com/android/server/wm/BackNavigationControllerTests.java
index dc3515d..a3fb717 100644
--- a/services/tests/wmtests/src/com/android/server/wm/BackNavigationControllerTests.java
+++ b/services/tests/wmtests/src/com/android/server/wm/BackNavigationControllerTests.java
@@ -42,7 +42,7 @@
 import android.platform.test.annotations.Presubmit;
 import android.view.WindowManager;
 import android.window.BackAnimationAdapter;
-import android.window.BackEvent;
+import android.window.BackMotionEvent;
 import android.window.BackNavigationInfo;
 import android.window.IOnBackInvokedCallback;
 import android.window.OnBackInvokedCallback;
@@ -259,11 +259,11 @@
     private IOnBackInvokedCallback createOnBackInvokedCallback() {
         return new IOnBackInvokedCallback.Stub() {
             @Override
-            public void onBackStarted(BackEvent backEvent) {
+            public void onBackStarted(BackMotionEvent backMotionEvent) {
             }
 
             @Override
-            public void onBackProgressed(BackEvent backEvent) {
+            public void onBackProgressed(BackMotionEvent backMotionEvent) {
             }
 
             @Override