diff --git a/java/com/android/incallui/AndroidManifest.xml b/java/com/android/incallui/AndroidManifest.xml
index 832a5e8..7286b0d 100644
--- a/java/com/android/incallui/AndroidManifest.xml
+++ b/java/com/android/incallui/AndroidManifest.xml
@@ -106,6 +106,13 @@
         android:theme="@style/Theme.Incall.DialogHolder"
         />
 
+    <activity
+        android:excludeFromRecents="true"
+        android:exported="false"
+        android:name="com.android.incallui.PostCharDialogActivity"
+        android:noHistory="true"
+        android:theme="@style/Theme.Incall.DialogHolder"/>
+
     <!-- BroadcastReceiver for receiving Intents from Notification mechanism. -->
     <receiver
         android:directBootAware="true"
diff --git a/java/com/android/incallui/InCallActivity.java b/java/com/android/incallui/InCallActivity.java
index 2b6c2b4..02335b6 100644
--- a/java/com/android/incallui/InCallActivity.java
+++ b/java/com/android/incallui/InCallActivity.java
@@ -145,8 +145,6 @@
   private View pseudoBlackScreenOverlay;
   private SelectPhoneAccountDialogFragment selectPhoneAccountDialogFragment;
   private String dtmfTextToPrepopulate;
-  private String showPostCharWaitDialogCallId;
-  private String showPostCharWaitDialogChars;
   private boolean allowOrientationChange;
   private boolean animateDialpadOnShow;
   private boolean didShowAnswerScreen;
@@ -160,7 +158,6 @@
   private boolean isRecreating; // whether the activity is going to be recreated
   private boolean isVisible;
   private boolean needDismissPendingDialogs;
-  private boolean showPostCharWaitDialogOnResume;
   private boolean touchDownWhenPseudoScreenOff;
   private int[] backgroundDrawableColors;
   @DialpadRequestType private int showDialpadRequest = DIALPAD_REQUEST_NONE;
@@ -531,10 +528,6 @@
     }
     updateNavigationBar(isDialpadVisible());
 
-    if (showPostCharWaitDialogOnResume) {
-      showDialogForPostCharWait(showPostCharWaitDialogCallId, showPostCharWaitDialogChars);
-    }
-
     CallList.getInstance()
         .onInCallUiShown(getIntent().getBooleanExtra(IntentExtraNames.FOR_FULL_SCREEN, false));
 
@@ -1016,18 +1009,8 @@
   }
 
   public void showDialogForPostCharWait(String callId, String chars) {
-    if (isVisible) {
-      PostCharDialogFragment fragment = new PostCharDialogFragment(callId, chars);
-      fragment.show(getSupportFragmentManager(), Tags.POST_CHAR_DIALOG_FRAGMENT);
-
-      showPostCharWaitDialogOnResume = false;
-      showPostCharWaitDialogCallId = null;
-      showPostCharWaitDialogChars = null;
-    } else {
-      showPostCharWaitDialogOnResume = true;
-      showPostCharWaitDialogCallId = callId;
-      showPostCharWaitDialogChars = chars;
-    }
+    PostCharDialogFragment fragment = new PostCharDialogFragment(callId, chars);
+    fragment.show(getSupportFragmentManager(), Tags.POST_CHAR_DIALOG_FRAGMENT);
   }
 
   public void showDialogOrToastForDisconnectedCall(DisconnectMessage disconnectMessage) {
diff --git a/java/com/android/incallui/InCallPresenter.java b/java/com/android/incallui/InCallPresenter.java
index 526cc64..6e7daf5 100644
--- a/java/com/android/incallui/InCallPresenter.java
+++ b/java/com/android/incallui/InCallPresenter.java
@@ -1271,8 +1271,22 @@
   }
 
   public void onPostDialCharWait(String callId, String chars) {
-    if (isActivityStarted()) {
+    // If not visible, inCallActivity is stopped. Starting from P, calling recreate() will destroy
+    // the old activity instance and create a new instance immediately. Previously, the old activity
+    // went through its lifecycle from create to destroy before creating a new instance.
+    // So this case doesn't work now: make a call with char WAIT, leave in call UI, call gets
+    // connected, and go back to in call UI to see the dialog.
+    // So we should show dialog in an empty activity if inCallActivity is not visible. And it also
+    // helps with background calling.
+    if (isActivityStarted() && inCallActivity.isVisible()) {
       inCallActivity.showDialogForPostCharWait(callId, chars);
+    } else {
+      Intent intent = new Intent(context, PostCharDialogActivity.class);
+      // Prevent showing MainActivity with PostCharDialogActivity on above
+      intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_MULTIPLE_TASK);
+      intent.putExtra(PostCharDialogActivity.EXTRA_CALL_ID, callId);
+      intent.putExtra(PostCharDialogActivity.EXTRA_POST_DIAL_STRING, chars);
+      context.startActivity(intent);
     }
   }
 
diff --git a/java/com/android/incallui/PostCharDialogActivity.java b/java/com/android/incallui/PostCharDialogActivity.java
new file mode 100644
index 0000000..dcdc9d6
--- /dev/null
+++ b/java/com/android/incallui/PostCharDialogActivity.java
@@ -0,0 +1,100 @@
+/*
+ * Copyright (C) 2018 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 com.android.incallui;
+
+import android.os.Bundle;
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+import android.support.v7.app.AppCompatActivity;
+import com.android.incallui.call.CallList;
+import com.android.incallui.call.DialerCall;
+
+/**
+ * Activity that contains an alert dialog with OK and Cancel buttons to allow user to Accept or
+ * Reject the WAIT inserted as part of the Dial string.
+ */
+public class PostCharDialogActivity extends AppCompatActivity implements CallList.Listener {
+
+  public static final String EXTRA_CALL_ID = "extra_call_id";
+  public static final String EXTRA_POST_DIAL_STRING = "extra_post_dial_string";
+  private static final String TAG_INTERNATIONAL_CALL_ON_WIFI = "tag_international_call_on_wifi";
+
+  private String callId;
+
+  @Override
+  protected void onCreate(@Nullable Bundle bundle) {
+    super.onCreate(bundle);
+
+    callId = getIntent().getStringExtra(EXTRA_CALL_ID);
+    String postDialString = getIntent().getStringExtra(EXTRA_POST_DIAL_STRING);
+    if (callId == null || postDialString == null) {
+      finish();
+      return;
+    }
+
+    PostCharDialogFragment fragment = new PostCharDialogFragment(callId, postDialString);
+    fragment.show(getSupportFragmentManager(), TAG_INTERNATIONAL_CALL_ON_WIFI);
+
+    CallList.getInstance().addListener(this);
+  }
+
+  @Override
+  protected void onDestroy() {
+    super.onDestroy();
+    CallList.getInstance().removeListener(this);
+  }
+
+  @Override
+  protected void onPause() {
+    super.onPause();
+    // We don't expect the activity to resume, except for orientation change.
+    if (!isChangingConfigurations()) {
+      finish();
+    }
+  }
+
+  @Override
+  public void onDisconnect(DialerCall call) {
+    if (callId.equals(call.getId())) {
+      finish();
+    }
+  }
+
+  @Override
+  public void onIncomingCall(DialerCall call) {}
+
+  @Override
+  public void onUpgradeToVideo(DialerCall call) {}
+
+  @Override
+  public void onUpgradeToRtt(DialerCall call, int rttRequestId) {}
+
+  @Override
+  public void onSessionModificationStateChange(DialerCall call) {}
+
+  @Override
+  public void onCallListChange(CallList callList) {}
+
+  @Override
+  public void onWiFiToLteHandover(DialerCall call) {}
+
+  @Override
+  public void onHandoverToWifiFailed(DialerCall call) {}
+
+  @Override
+  public void onInternationalCallOnWifi(@NonNull DialerCall call) {}
+}
diff --git a/java/com/android/incallui/PostCharDialogFragment.java b/java/com/android/incallui/PostCharDialogFragment.java
index 4bcc68e..1d06fd4 100644
--- a/java/com/android/incallui/PostCharDialogFragment.java
+++ b/java/com/android/incallui/PostCharDialogFragment.java
@@ -55,7 +55,8 @@
     buf.append(getResources().getText(R.string.wait_prompt_str));
     buf.append(postDialStr);
 
-    final AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
+    final AlertDialog.Builder builder =
+        new AlertDialog.Builder(getActivity(), R.style.AlertDialogTheme);
     builder.setMessage(buf.toString());
 
     builder.setPositiveButton(