Add fancy animation for IA fragment

The animation of IA fragment is very choppy on expanding or collapsing
conditionals. So adding LayoutTransition for IA fragment makes the
animation more smoothly.

Bug: 123536786
Bug: 123537499
Test: visual, robotests
Change-Id: I731db8556ac392c9ab98bd292498ccf6c87295fb

res/layout/settings_homepage_container.xml

@@ -44,7 +44,8 @@
             <FrameLayout
                 android:id="@+id/main_content"
                 android:layout_width="match_parent"
-                android:layout_height="wrap_content"/>
+                android:layout_height="wrap_content"
+                android:animateLayoutChanges="true"/>
 
         </LinearLayout>
     </androidx.core.widget.NestedScrollView>

src/com/android/settings/homepage/SettingsHomepageActivity.java

@@ -16,11 +16,13 @@
 
 package com.android.settings.homepage;
 
+import android.animation.LayoutTransition;
 import android.app.settings.SettingsEnums;
 import android.content.Intent;
 import android.os.Bundle;
 import android.util.FeatureFlagUtils;
 import android.view.View;
+import android.widget.FrameLayout;
 import android.widget.ImageView;
 import android.widget.Toolbar;
 
@@ -64,6 +66,8 @@ public class SettingsHomepageActivity extends SettingsBaseActivity {
 
         showFragment(new ContextualCardsFragment(), R.id.contextual_cards_content);
         showFragment(new TopLevelSettings(), R.id.main_content);
+        ((FrameLayout) findViewById(R.id.main_content))
+                .getLayoutTransition().enableTransitionType(LayoutTransition.CHANGING);
     }
 
     private void showFragment(Fragment fragment, int id) {

tests/robotests/src/com/android/settings/homepage/SettingsHomepageActivityTest.java

@@ -20,6 +20,7 @@ import static com.google.common.truth.Truth.assertThat;
 
 import android.util.FeatureFlagUtils;
 import android.view.View;
+import android.widget.FrameLayout;
 
 import com.android.settings.R;
 import com.android.settings.SettingsActivity;
@@ -65,4 +66,13 @@ public class SettingsHomepageActivityTest {
         assertThat(actualPaddingTop).isEqualTo(
                 statusBarHeight + searchBarHeight + searchBarMargin * 2);
     }
+
+    @Test
+    public void launch_shouldHaveAnimationForIaFragment() {
+        final SettingsHomepageActivity activity = Robolectric.buildActivity(
+                SettingsHomepageActivity.class).create().get();
+        final FrameLayout frameLayout = activity.findViewById(R.id.main_content);
+
+        assertThat(frameLayout.getLayoutTransition()).isNotNull();
+    }
 }