diff --git a/core/java/android/inputmethodservice/InputMethodService.java b/core/java/android/inputmethodservice/InputMethodService.java
index 6831eca32f726..df9a7c2cb5860 100644
--- a/core/java/android/inputmethodservice/InputMethodService.java
+++ b/core/java/android/inputmethodservice/InputMethodService.java
@@ -1700,8 +1700,12 @@ public class InputMethodService extends AbstractInputMethodService {
         if (config.orientation != Configuration.ORIENTATION_LANDSCAPE) {
             return false;
         }
-        if (mInputEditorInfo != null
-                && (mInputEditorInfo.imeOptions & EditorInfo.IME_FLAG_NO_FULLSCREEN) != 0) {
+        if ((mInputEditorInfo != null
+                && (mInputEditorInfo.imeOptions & EditorInfo.IME_FLAG_NO_FULLSCREEN) != 0)
+                // If app window has portrait orientation, regardless of what display orientation
+                // is, IME shouldn't use fullscreen-mode.
+                || (mInputEditorInfo.internalImeOptions
+                        & EditorInfo.IME_FLAG_APP_WINDOW_PORTRAIT) != 0) {
             return false;
         }
         return true;
diff --git a/core/java/android/view/inputmethod/EditorInfo.java b/core/java/android/view/inputmethod/EditorInfo.java
index 7dbf693699964..1cf25a77fa38a 100644
--- a/core/java/android/view/inputmethod/EditorInfo.java
+++ b/core/java/android/view/inputmethod/EditorInfo.java
@@ -28,6 +28,7 @@ import android.annotation.IntDef;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
+import android.content.res.Configuration;
 import android.os.Build.VERSION_CODES;
 import android.os.Bundle;
 import android.os.LocaleList;
@@ -292,6 +293,13 @@ public class EditorInfo implements InputType, Parcelable {
      */
     public static final int IME_FLAG_FORCE_ASCII = 0x80000000;
 
+    /**
+     * Flag of {@link #internalImeOptions}: flag is set when app window containing this
+     * {@link EditorInfo} is using {@link Configuration#ORIENTATION_PORTRAIT} mode.
+     * @hide
+     */
+    public static final int IME_FLAG_APP_WINDOW_PORTRAIT = 0x80000000;
+
     /**
      * Generic unspecified type for {@link #imeOptions}.
      */
@@ -312,6 +320,7 @@ public class EditorInfo implements InputType, Parcelable {
      *                               1 1 IME_ACTION_NEXT
      *                               11  IME_ACTION_DONE
      *                               111 IME_ACTION_PREVIOUS
+     *          1                        IME_FLAG_APP_WINDOW_PORTRAIT
      *         1                         IME_FLAG_NO_PERSONALIZED_LEARNING
      *        1                          IME_FLAG_NO_FULLSCREEN
      *       1                           IME_FLAG_NAVIGATE_PREVIOUS
@@ -342,6 +351,20 @@ public class EditorInfo implements InputType, Parcelable {
      */
     public String privateImeOptions = null;
 
+    /**
+     * Masks for {@link internalImeOptions}
+     *
+     * <pre>
+     *  1                                IME_FLAG_APP_WINDOW_PORTRAIT
+     * |-------|-------|-------|-------|</pre>
+     */
+
+    /**
+     * Same as {@link android.R.attr#imeOptions} but for framework's internal-use only.
+     * @hide
+     */
+    public int internalImeOptions = IME_NULL;
+
     /**
      * In some cases an IME may be able to display an arbitrary label for
      * a command the user can perform, which you can specify here. This is
diff --git a/core/java/android/widget/TextView.java b/core/java/android/widget/TextView.java
index 12c91fac0c65a..977a0e89a143d 100644
--- a/core/java/android/widget/TextView.java
+++ b/core/java/android/widget/TextView.java
@@ -17,6 +17,7 @@
 package android.widget;
 
 import static android.Manifest.permission.INTERACT_ACROSS_USERS_FULL;
+import static android.content.res.Configuration.ORIENTATION_PORTRAIT;
 import static android.view.ContentInfo.FLAG_CONVERT_TO_PLAIN_TEXT;
 import static android.view.ContentInfo.SOURCE_AUTOFILL;
 import static android.view.ContentInfo.SOURCE_CLIPBOARD;
@@ -8738,6 +8739,9 @@ public class TextView extends View implements ViewTreeObserver.OnPreDrawListener
                     outAttrs.imeOptions |= EditorInfo.IME_FLAG_NO_ENTER_ACTION;
                 }
             }
+            if (getResources().getConfiguration().orientation == ORIENTATION_PORTRAIT) {
+                outAttrs.internalImeOptions |= EditorInfo.IME_FLAG_APP_WINDOW_PORTRAIT;
+            }
             if (isMultilineInputType(outAttrs.inputType)) {
                 // Multi-line text editors should always show an enter key.
                 outAttrs.imeOptions |= EditorInfo.IME_FLAG_NO_ENTER_ACTION;
diff --git a/core/tests/coretests/src/android/widget/TextViewTest.java b/core/tests/coretests/src/android/widget/TextViewTest.java
index 40ecf9a83981d..66fdfff990f8e 100644
--- a/core/tests/coretests/src/android/widget/TextViewTest.java
+++ b/core/tests/coretests/src/android/widget/TextViewTest.java
@@ -16,6 +16,9 @@
 
 package android.widget;
 
+import static android.content.pm.ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE;
+import static android.content.pm.ActivityInfo.SCREEN_ORIENTATION_PORTRAIT;
+
 import static junit.framework.Assert.assertEquals;
 import static junit.framework.Assert.assertFalse;
 import static junit.framework.Assert.assertNotNull;
@@ -30,6 +33,7 @@ import android.text.GetChars;
 import android.text.Layout;
 import android.text.PrecomputedText;
 import android.view.View;
+import android.view.inputmethod.EditorInfo;
 import android.widget.TextView.BufferType;
 
 import androidx.test.InstrumentationRegistry;
@@ -254,6 +258,24 @@ public class TextViewTest {
         assertEquals("", mTextView.getTransformed().toString());
     }
 
+    @Test
+    @UiThreadTest
+    public void testPortraitDoesntSupportFullscreenIme() {
+        mActivity.setRequestedOrientation(SCREEN_ORIENTATION_PORTRAIT);
+        mTextView = new NullSetTextTextView(mActivity);
+        mTextView.requestFocus();
+        assertEquals("IME_FLAG_NO_FULLSCREEN should be set",
+                mTextView.getImeOptions(),
+                mTextView.getImeOptions() & EditorInfo.IME_FLAG_NO_FULLSCREEN);
+
+        mTextView.clearFocus();
+        mActivity.setRequestedOrientation(SCREEN_ORIENTATION_LANDSCAPE);
+        mTextView = new NullSetTextTextView(mActivity);
+        mTextView.requestFocus();
+        assertEquals("IME_FLAG_NO_FULLSCREEN should not be set",
+                0, mTextView.getImeOptions() & EditorInfo.IME_FLAG_NO_FULLSCREEN);
+    }
+
     private String createLongText() {
         int size = 600 * 1000;
         final StringBuilder builder = new StringBuilder(size);