diff --git a/Android.bp b/Android.bp
index 9584767..eafb605 100644
--- a/Android.bp
+++ b/Android.bp
@@ -376,6 +376,7 @@
         "core/java/android/view/IApplicationToken.aidl",
         "core/java/android/view/IAppTransitionAnimationSpecsFuture.aidl",
         "core/java/android/view/IDockedStackListener.aidl",
+        "core/java/android/view/IDisplayFoldListener.aidl",
         "core/java/android/view/IGraphicsStats.aidl",
         "core/java/android/view/IGraphicsStatsCallback.aidl",
         "core/java/android/view/IInputFilter.aidl",
diff --git a/core/java/android/view/IDisplayFoldListener.aidl b/core/java/android/view/IDisplayFoldListener.aidl
new file mode 100644
index 0000000..2c91149
--- /dev/null
+++ b/core/java/android/view/IDisplayFoldListener.aidl
@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2019 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.view;
+
+/**
+ * {@hide}
+ */
+oneway interface IDisplayFoldListener
+{
+    /** Called when the foldedness of a display changes */
+    void onDisplayFoldChanged(int displayId, boolean folded);
+}
diff --git a/core/java/android/view/IWindowManager.aidl b/core/java/android/view/IWindowManager.aidl
index 42ac880..8ae4757 100644
--- a/core/java/android/view/IWindowManager.aidl
+++ b/core/java/android/view/IWindowManager.aidl
@@ -34,6 +34,7 @@
 import android.view.IApplicationToken;
 import android.view.IAppTransitionAnimationSpecsFuture;
 import android.view.IDockedStackListener;
+import android.view.IDisplayFoldListener;
 import android.view.IOnKeyguardExitResult;
 import android.view.IPinnedStackListener;
 import android.view.RemoteAnimationAdapter;
@@ -403,6 +404,16 @@
     Region getCurrentImeTouchRegion();
 
     /**
+     * Registers an IDisplayFoldListener.
+     */
+    void registerDisplayFoldListener(IDisplayFoldListener listener);
+
+    /**
+     * Unregisters an IDisplayFoldListener.
+     */
+    void unregisterDisplayFoldListener(IDisplayFoldListener listener);
+
+    /**
      * Starts a window trace.
      */
     void startWindowTrace();
diff --git a/services/core/java/com/android/server/policy/DisplayFoldController.java b/services/core/java/com/android/server/policy/DisplayFoldController.java
index 71d6dfc..fdcafa7 100644
--- a/services/core/java/com/android/server/policy/DisplayFoldController.java
+++ b/services/core/java/com/android/server/policy/DisplayFoldController.java
@@ -23,8 +23,13 @@
 import android.hardware.SensorEventListener;
 import android.hardware.SensorManager;
 import android.hardware.display.DisplayManagerInternal;
+import android.os.Handler;
+import android.os.RemoteCallbackList;
+import android.os.RemoteException;
 import android.view.DisplayInfo;
+import android.view.IDisplayFoldListener;
 
+import com.android.server.DisplayThread;
 import com.android.server.LocalServices;
 import com.android.server.wm.WindowManagerInternal;
 
@@ -40,16 +45,24 @@
 
     /** The display area while device is folded. */
     private final Rect mFoldedArea;
+    private final Handler mHandler;
 
     private final DisplayInfo mNonOverrideDisplayInfo = new DisplayInfo();
+    private final RemoteCallbackList<IDisplayFoldListener> mListeners = new RemoteCallbackList<>();
     private Boolean mFolded;
 
     DisplayFoldController(WindowManagerInternal windowManagerInternal,
-            DisplayManagerInternal displayManagerInternal, int displayId, Rect foldedArea) {
+            DisplayManagerInternal displayManagerInternal, int displayId, Rect foldedArea,
+            Handler handler) {
         mWindowManagerInternal = windowManagerInternal;
         mDisplayManagerInternal = displayManagerInternal;
         mDisplayId = displayId;
         mFoldedArea = new Rect(foldedArea);
+        mHandler = handler;
+    }
+
+    void requestDeviceFolded(boolean folded) {
+        mHandler.post(() -> setDeviceFolded(folded));
     }
 
     void setDeviceFolded(boolean folded) {
@@ -71,6 +84,34 @@
             mDisplayManagerInternal.setDisplayOffsets(mDisplayId, 0, 0);
         }
         mFolded = folded;
+
+        final int n = mListeners.beginBroadcast();
+        for (int i = 0; i < n; i++) {
+            try {
+                mListeners.getBroadcastItem(i).onDisplayFoldChanged(mDisplayId, folded);
+            } catch (RemoteException e) {
+                // Listener died.
+            }
+        }
+        mListeners.finishBroadcast();
+    }
+
+    void registerDisplayFoldListener(IDisplayFoldListener listener) {
+        mListeners.register(listener);
+        if (mFolded == null) {
+            return;
+        }
+        mHandler.post(() -> {
+            try {
+                listener.onDisplayFoldChanged(mDisplayId, mFolded);
+            } catch (RemoteException e) {
+                // Listener died.
+            }
+        });
+    }
+
+    void unregisterDisplayFoldListener(IDisplayFoldListener listener) {
+        mListeners.unregister(listener);
     }
 
     /**
@@ -88,7 +129,7 @@
         sensorManager.registerListener(new SensorEventListener() {
             @Override
             public void onSensorChanged(SensorEvent event) {
-                result.setDeviceFolded(event.values[0] < 1f);
+                result.requestDeviceFolded(event.values[0] < 1f);
             }
 
             @Override
@@ -109,6 +150,6 @@
                 displayInfo.logicalWidth, displayInfo.logicalHeight);
 
         return new DisplayFoldController(LocalServices.getService(WindowManagerInternal.class),
-                displayService, displayId, foldedArea);
+                displayService, displayId, foldedArea, DisplayThread.getHandler());
     }
 }
diff --git a/services/core/java/com/android/server/policy/PhoneWindowManager.java b/services/core/java/com/android/server/policy/PhoneWindowManager.java
index 25cfc72..0796a9c 100644
--- a/services/core/java/com/android/server/policy/PhoneWindowManager.java
+++ b/services/core/java/com/android/server/policy/PhoneWindowManager.java
@@ -177,6 +177,7 @@
 import android.util.proto.ProtoOutputStream;
 import android.view.Display;
 import android.view.HapticFeedbackConstants;
+import android.view.IDisplayFoldListener;
 import android.view.IWindowManager;
 import android.view.InputDevice;
 import android.view.KeyCharacterMap;
@@ -3205,6 +3206,20 @@
     }
 
     @Override
+    public void registerDisplayFoldListener(IDisplayFoldListener listener) {
+        if (mDisplayFoldController != null) {
+            mDisplayFoldController.registerDisplayFoldListener(listener);
+        }
+    }
+
+    @Override
+    public void unregisterDisplayFoldListener(IDisplayFoldListener listener) {
+        if (mDisplayFoldController != null) {
+            mDisplayFoldController.unregisterDisplayFoldListener(listener);
+        }
+    }
+
+    @Override
     public void registerShortcutKey(long shortcutCode, IShortcutService shortcutService)
             throws RemoteException {
         synchronized (mLock) {
@@ -4984,7 +4999,7 @@
     private void applyLidSwitchState() {
         final int lidState = mDefaultDisplayPolicy.getLidState();
         if (mLidControlsDisplayFold && mDisplayFoldController != null) {
-            mDisplayFoldController.setDeviceFolded(lidState == LID_CLOSED);
+            mDisplayFoldController.requestDeviceFolded(lidState == LID_CLOSED);
         } else if (lidState == LID_CLOSED && mLidControlsSleep) {
             goToSleep(SystemClock.uptimeMillis(), PowerManager.GO_TO_SLEEP_REASON_LID_SWITCH,
                     PowerManager.GO_TO_SLEEP_FLAG_NO_DOZE);
diff --git a/services/core/java/com/android/server/policy/WindowManagerPolicy.java b/services/core/java/com/android/server/policy/WindowManagerPolicy.java
index 1d82970..e18cd17 100644
--- a/services/core/java/com/android/server/policy/WindowManagerPolicy.java
+++ b/services/core/java/com/android/server/policy/WindowManagerPolicy.java
@@ -78,6 +78,7 @@
 import android.util.proto.ProtoOutputStream;
 import android.view.Display;
 import android.view.IApplicationToken;
+import android.view.IDisplayFoldListener;
 import android.view.IWindowManager;
 import android.view.InputEventReceiver;
 import android.view.KeyEvent;
@@ -1457,6 +1458,16 @@
     public void requestUserActivityNotification();
 
     /**
+     * Registers an IDisplayFoldListener.
+     */
+    default void registerDisplayFoldListener(IDisplayFoldListener listener) {}
+
+    /**
+     * Unregisters an IDisplayFoldListener.
+     */
+    default void unregisterDisplayFoldListener(IDisplayFoldListener listener) {}
+
+    /**
      * Updates the flag about whether AOD is showing.
      *
      * @return whether the value was changed.
diff --git a/services/core/java/com/android/server/wm/WindowManagerService.java b/services/core/java/com/android/server/wm/WindowManagerService.java
index 12b858c..8373b44 100644
--- a/services/core/java/com/android/server/wm/WindowManagerService.java
+++ b/services/core/java/com/android/server/wm/WindowManagerService.java
@@ -192,6 +192,7 @@
 import android.view.DisplayInfo;
 import android.view.Gravity;
 import android.view.IAppTransitionAnimationSpecsFuture;
+import android.view.IDisplayFoldListener;
 import android.view.IDockedStackListener;
 import android.view.IInputFilter;
 import android.view.IOnKeyguardExitResult;
@@ -3748,6 +3749,16 @@
     }
 
     @Override
+    public void registerDisplayFoldListener(IDisplayFoldListener listener) {
+        mPolicy.registerDisplayFoldListener(listener);
+    }
+
+    @Override
+    public void unregisterDisplayFoldListener(IDisplayFoldListener listener) {
+        mPolicy.unregisterDisplayFoldListener(listener);
+    }
+
+    @Override
     public int getPreferredOptionsPanelGravity(int displayId) {
         synchronized (mGlobalLock) {
             final DisplayContent displayContent = mRoot.getDisplayContent(displayId);