Fixed incall UI to emulate single party call correctly when one
participant dropped during conference creation.

Test: atest com.android.services.telephony.ImsConferenceTest#testSinglePartyEmulationWithOneParticipantAtBegining
Bug: 141927833
Merged-In: I2048ab6fbad428e1ae2fb2d65c7c95f541e131c2
Change-Id: I2048ab6fbad428e1ae2fb2d65c7c95f541e131c2
(cherry picked from commit cebf18cb5d2cc9ec6e8f8513dfc050e578246d60)
diff --git a/src/com/android/services/telephony/ImsConference.java b/src/com/android/services/telephony/ImsConference.java
index 245f2e8..4da92e2 100644
--- a/src/com/android/services/telephony/ImsConference.java
+++ b/src/com/android/services/telephony/ImsConference.java
@@ -829,7 +829,7 @@
             // If the single party call emulation fature flag is enabled, we can potentially treat
             // the conference as a single party call when there is just one participant.
             if (mFeatureFlagProxy.isUsingSinglePartyCallEmulation()) {
-                if (oldParticipantCount > 1 && newParticipantCount == 1) {
+                if (oldParticipantCount != 1 && newParticipantCount == 1) {
                     // If number of participants goes to 1, emulate a single party call.
                     startEmulatingSinglePartyCall();
                 } else if (mIsEmulatingSinglePartyCall && !isSinglePartyConference) {
@@ -1312,4 +1312,12 @@
         return isMaximumConferenceSizeEnforced()
                 && getNumberOfParticipants() >= getMaximumConferenceSize();
     }
+
+    /**
+     * @return {@code True} if the ImsConference is emulating single party call.
+     */
+    @VisibleForTesting
+    public boolean isEmulatingSinglePartyCall() {
+        return mIsEmulatingSinglePartyCall;
+    }
 }
diff --git a/tests/src/com/android/services/telephony/ImsConferenceTest.java b/tests/src/com/android/services/telephony/ImsConferenceTest.java
index 68b5b3b..568549b 100644
--- a/tests/src/com/android/services/telephony/ImsConferenceTest.java
+++ b/tests/src/com/android/services/telephony/ImsConferenceTest.java
@@ -16,19 +16,16 @@
 
 package com.android.services.telephony;
 
-import static org.mockito.Matchers.eq;
-import static org.mockito.Mockito.doAnswer;
-import static org.mockito.Mockito.doNothing;
-import static org.mockito.Mockito.never;
-import static org.mockito.Mockito.reset;
-import static org.mockito.Mockito.verify;
-import static org.mockito.Mockito.when;
-import static org.mockito.Mockito.any;
-import static org.mockito.Mockito.times;
-
-import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.mockito.Matchers.eq;
+import static org.mockito.Mockito.any;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.reset;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
 
 import android.net.Uri;
 import android.os.Looper;
@@ -39,15 +36,10 @@
 import android.telecom.PhoneAccountHandle;
 import android.test.suitebuilder.annotation.SmallTest;
 
-import com.android.internal.telephony.PhoneConstants;
-
 import org.junit.Before;
 import org.junit.Test;
-
 import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
-import org.mockito.invocation.InvocationOnMock;
-import org.mockito.stubbing.Answer;
 
 import java.util.Arrays;
 
@@ -179,6 +171,31 @@
     }
 
     /**
+     * Verify that the single party emulate correctly when the conference start with only
+     * one participant.
+     */
+    @Test
+    @SmallTest
+    public void testSinglePartyEmulationWithOneParticipantAtBeginning() {
+        when(mMockTelecomAccountRegistry.isUsingSimCallManager(any(PhoneAccountHandle.class)))
+                .thenReturn(false);
+
+        ImsConference imsConference = new ImsConference(mMockTelecomAccountRegistry,
+                mMockTelephonyConnectionServiceProxy, mConferenceHost,
+                null /* phoneAccountHandle */, () -> true /* featureFlagProxy */);
+
+        ConferenceParticipant participant1 = new ConferenceParticipant(
+                Uri.parse("tel:6505551212"),
+                "A",
+                Uri.parse("sip:6505551212@testims.com"),
+                Connection.STATE_ACTIVE,
+                Call.Details.DIRECTION_INCOMING);
+        imsConference.handleConferenceParticipantsUpdate(mConferenceHost,
+                Arrays.asList(participant1));
+        assertTrue(imsConference.isEmulatingSinglePartyCall());
+    }
+
+    /**
      * Verify that we do not use single party emulation when a sim call manager is in use.
      */
     @Test