diff --git a/core/java/android/view/ImeFocusController.java b/core/java/android/view/ImeFocusController.java
index 2d2b0f5369d15..f4daec121fc60 100644
--- a/core/java/android/view/ImeFocusController.java
+++ b/core/java/android/view/ImeFocusController.java
@@ -136,45 +136,58 @@ public final class ImeFocusController {
 
         boolean forceFocus = false;
         final InputMethodManagerDelegate immDelegate = getImmDelegate();
-        if (immDelegate.isRestartOnNextWindowFocus(true /* reset */)) {
-            if (DEBUG) Log.v(TAG, "Restarting due to isRestartOnNextWindowFocus as true");
-            forceFocus = true;
-        }
+        synchronized (immDelegate.getLockObject()) {
+            // TODO(b/244504062): Remove isRestartOnNextWindowFocus.
+            if (immDelegate.isRestartOnNextWindowFocus(true /* reset */)) {
+                if (DEBUG) Log.v(TAG, "Restarting due to isRestartOnNextWindowFocus as true");
+                forceFocus = true;
+            }
 
-        // Update mNextServedView when focusedView changed.
-        onViewFocusChanged(viewForWindowFocus, true);
+            // Update mNextServedView when focusedView changed.
+            onViewFocusChanged(viewForWindowFocus, true);
 
-        // Starting new input when the next focused view is same as served view but the currently
-        // active connection (if any) is not associated with it.
-        final boolean nextFocusIsServedView = mServedView == viewForWindowFocus;
-        if (nextFocusIsServedView && !immDelegate.hasActiveConnection(viewForWindowFocus)) {
-            forceFocus = true;
+            // Starting new input when the next focused view is same as served view but the
+            // currently active connection (if any) is not associated with it.
+            final boolean nextFocusIsServedView = mServedView == viewForWindowFocus;
+
+            if (nextFocusIsServedView && !immDelegate.hasActiveConnection(viewForWindowFocus)) {
+                forceFocus = true;
+            }
         }
 
         immDelegate.startInputAsyncOnWindowFocusGain(viewForWindowFocus,
                 windowAttribute.softInputMode, windowAttribute.flags, forceFocus);
     }
 
+    /**
+     * @see InputMethodManager#checkFocus()
+     */
     public boolean checkFocus(boolean forceNewFocus, boolean startInput) {
         final InputMethodManagerDelegate immDelegate = getImmDelegate();
-        if (!immDelegate.isCurrentRootView(mViewRootImpl)
-                || (mServedView == mNextServedView && !forceNewFocus)) {
-            return false;
+        synchronized (immDelegate.getLockObject()) {
+            if (!immDelegate.isCurrentRootView(mViewRootImpl)) {
+                return false;
+            }
+            if (mServedView == mNextServedView && !forceNewFocus) {
+                return false;
+            }
+            if (DEBUG) {
+                Log.v(TAG, "checkFocus: view=" + mServedView
+                        + " next=" + mNextServedView
+                        + " force=" + forceNewFocus
+                        + " package="
+                        + (mServedView != null ? mServedView.getContext().getPackageName()
+                        : "<none>"));
+            }
+            // Close the connection when no next served view coming.
+            if (mNextServedView == null) {
+                immDelegate.finishInput();
+                immDelegate.closeCurrentIme();
+                return false;
+            }
+            mServedView = mNextServedView;
+            immDelegate.finishComposingText();
         }
-        if (DEBUG) Log.v(TAG, "checkFocus: view=" + mServedView
-                + " next=" + mNextServedView
-                + " force=" + forceNewFocus
-                + " package="
-                + (mServedView != null ? mServedView.getContext().getPackageName() : "<none>"));
-
-        // Close the connection when no next served view coming.
-        if (mNextServedView == null) {
-            immDelegate.finishInput();
-            immDelegate.closeCurrentIme();
-            return false;
-        }
-        mServedView = mNextServedView;
-        immDelegate.finishComposingText();
 
         if (startInput) {
             immDelegate.startInput(StartInputReason.CHECK_FOCUS, null /* focusedView */,
@@ -188,51 +201,61 @@ public final class ImeFocusController {
         if (view == null || view.isTemporarilyDetached()) {
             return;
         }
-        if (!getImmDelegate().isCurrentRootView(view.getViewRootImpl())) {
-            return;
-        }
-        if (!view.hasImeFocus() || !view.hasWindowFocus()) {
-            return;
-        }
-        if (DEBUG) Log.d(TAG, "onViewFocusChanged, view=" + InputMethodDebug.dumpViewInfo(view)
-                + ", mServedView=" + InputMethodDebug.dumpViewInfo(mServedView));
+        final InputMethodManagerDelegate immDelegate = getImmDelegate();
+        synchronized (immDelegate.getLockObject()) {
+            if (!immDelegate.isCurrentRootView(view.getViewRootImpl())) {
+                return;
+            }
+            if (!view.hasImeFocus() || !view.hasWindowFocus()) {
+                return;
+            }
+            if (DEBUG) {
+                Log.d(TAG, "onViewFocusChanged, view=" + InputMethodDebug.dumpViewInfo(view)
+                        + ", mServedView=" + InputMethodDebug.dumpViewInfo(mServedView));
+            }
 
-        // We don't need to track the next served view when the view lost focus here because:
-        // 1) The current view focus may be cleared temporary when in touch mode, closing input
-        //    at this moment isn't the right way.
-        // 2) We only care about the served view change when it focused, since changing input
-        //    connection when the focus target changed is reasonable.
-        // 3) Setting the next served view as null when no more served view should be handled in
-        //    other special events (e.g. view detached from window or the window dismissed).
-        if (hasFocus) {
-            mNextServedView = view;
+            // We don't need to track the next served view when the view lost focus here because:
+            // 1) The current view focus may be cleared temporary when in touch mode, closing input
+            //    at this moment isn't the right way.
+            // 2) We only care about the served view change when it focused, since changing input
+            //    connection when the focus target changed is reasonable.
+            // 3) Setting the next served view as null when no more served view should be handled in
+            //    other special events (e.g. view detached from window or the window dismissed).
+            if (hasFocus) {
+                mNextServedView = view;
+            }
         }
         mViewRootImpl.dispatchCheckFocus();
     }
 
     @UiThread
     void onViewDetachedFromWindow(View view) {
-        if (!getImmDelegate().isCurrentRootView(view.getViewRootImpl())) {
-            return;
-        }
-        if (mNextServedView == view) {
-            mNextServedView = null;
-        }
-        if (mServedView == view) {
-            mViewRootImpl.dispatchCheckFocus();
+        final InputMethodManagerDelegate immDelegate = getImmDelegate();
+        synchronized (immDelegate.getLockObject()) {
+            if (!immDelegate.isCurrentRootView(view.getViewRootImpl())) {
+                return;
+            }
+            if (mNextServedView == view) {
+                mNextServedView = null;
+            }
+            if (mServedView == view) {
+                mViewRootImpl.dispatchCheckFocus();
+            }
         }
     }
 
     @UiThread
     void onWindowDismissed() {
         final InputMethodManagerDelegate immDelegate = getImmDelegate();
-        if (!immDelegate.isCurrentRootView(mViewRootImpl)) {
-            return;
+        synchronized (immDelegate.getLockObject()) {
+            if (!immDelegate.isCurrentRootView(mViewRootImpl)) {
+                return;
+            }
+            if (mServedView != null) {
+                immDelegate.finishInput();
+            }
+            immDelegate.setCurrentRootView(null);
         }
-        if (mServedView != null) {
-            immDelegate.finishInput();
-        }
-        immDelegate.setCurrentRootView(null);
         mHasImeFocus = false;
     }
 
@@ -283,9 +306,21 @@ public final class ImeFocusController {
      * @hide
      */
     public interface InputMethodManagerDelegate {
+        /**
+         * Starts the input connection.
+         * Note that this method must not hold the {@link InputMethodManager} lock with
+         * {@link InputMethodManagerDelegate#getLockObject()} while {@link InputMethodManager}
+         * calling into app-code in different threads.
+         */
         boolean startInput(@StartInputReason int startInputReason, View focusedView,
                 @StartInputFlags int startInputFlags,
                 @WindowManager.LayoutParams.SoftInputModeFlags int softInputMode, int windowFlags);
+        /**
+         * Starts the input connection when gaining the window focus.
+         * Note that this method must not hold the {@link InputMethodManager} lock with
+         * {@link InputMethodManagerDelegate#getLockObject()} while {@link InputMethodManager}
+         * calling into app-code in different threads.
+         */
         void startInputAsyncOnWindowFocusGain(View rootView,
                 @WindowManager.LayoutParams.SoftInputModeFlags int softInputMode, int windowFlags,
                 boolean forceNewFocus);
@@ -302,8 +337,6 @@ public final class ImeFocusController {
          * Returns the {@code InputMethodManager#mH} lock object.
          * Used for {@link ImeFocusController} to guard the served view being accessed by
          * {@link InputMethodManager} in different threads.
-         *
-         * TODO(b/244504062): Use this to all places requires synchronization in controller.
          */
         Object getLockObject();
     }