diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHandedDisplayAreaOrganizer.java b/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHandedDisplayAreaOrganizer.java
index d1b3f1a2e8a54..390985c09dcc9 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHandedDisplayAreaOrganizer.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHandedDisplayAreaOrganizer.java
@@ -82,6 +82,14 @@ public class OneHandedDisplayAreaOrganizer extends DisplayAreaOrganizer {
                 @Override
                 public void onOneHandedAnimationStart(
                         OneHandedAnimationController.OneHandedTransitionAnimator animator) {
+                    final boolean isEntering = animator.getTransitionDirection()
+                            == TRANSITION_DIRECTION_TRIGGER;
+                    if (!mTransitionCallbacks.isEmpty()) {
+                        for (int i = mTransitionCallbacks.size() - 1; i >= 0; i--) {
+                            final OneHandedTransitionCallback cb = mTransitionCallbacks.get(i);
+                            cb.onStartTransition(isEntering);
+                        }
+                    }
                 }
 
                 @Override
@@ -266,11 +274,12 @@ public class OneHandedDisplayAreaOrganizer extends DisplayAreaOrganizer {
         mLastVisualDisplayBounds.offsetTo(0,
                 direction == TRANSITION_DIRECTION_TRIGGER ? offset : 0);
         for (int i = mTransitionCallbacks.size() - 1; i >= 0; i--) {
-            final OneHandedTransitionCallback callback = mTransitionCallbacks.get(i);
+            final OneHandedTransitionCallback cb = mTransitionCallbacks.get(i);
+            cb.onStartTransition(false /* isTransitioning */);
             if (direction == TRANSITION_DIRECTION_TRIGGER) {
-                callback.onStartFinished(getLastVisualDisplayBounds());
+                cb.onStartFinished(getLastVisualDisplayBounds());
             } else {
-                callback.onStopFinished(getLastVisualDisplayBounds());
+                cb.onStopFinished(getLastVisualDisplayBounds());
             }
         }
     }
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHandedTransitionCallback.java b/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHandedTransitionCallback.java
index 3af7c4b71d0ac..e8291862947b5 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHandedTransitionCallback.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/onehanded/OneHandedTransitionCallback.java
@@ -23,6 +23,12 @@ import android.graphics.Rect;
  * touch region.(e.g: one handed activated, user tap out regions of displayArea to stop one handed)
  */
 public interface OneHandedTransitionCallback {
+    /**
+     * Called when one handed mode entering or exiting transition starting
+     */
+    default void onStartTransition(boolean isEntering) {
+    }
+
     /**
      * Called when start one handed transition finished
      */
diff --git a/packages/SystemUI/src/com/android/systemui/wmshell/WMShell.java b/packages/SystemUI/src/com/android/systemui/wmshell/WMShell.java
index 81bb819d77eac..74077a2482d13 100644
--- a/packages/SystemUI/src/com/android/systemui/wmshell/WMShell.java
+++ b/packages/SystemUI/src/com/android/systemui/wmshell/WMShell.java
@@ -235,6 +235,14 @@ public final class WMShell extends SystemUI
         oneHanded.setThreeButtonModeEnabled(currentMode == NAV_BAR_MODE_3BUTTON);
 
         oneHanded.registerTransitionCallback(new OneHandedTransitionCallback() {
+            @Override
+            public void onStartTransition(boolean isEntering) {
+                mSysUiMainExecutor.execute(() -> {
+                    mSysUiState.setFlag(SYSUI_STATE_ONE_HANDED_ACTIVE,
+                            true).commitUpdate(DEFAULT_DISPLAY);
+                });
+            }
+
             @Override
             public void onStartFinished(Rect bounds) {
                 mSysUiMainExecutor.execute(() -> {