Refactor CaptionPropertiesFragment to improve maintainability

Root cause: There is a bunch of different logic of preferences in CaptionPropertiesFragment. It’s hard to implement new features and hard to maintain and hard to be testable.
Solution: Move out different logic of CaptionPropertiesFragment into controllers to reduce the complexity of the relationship between preference and fragment.

Bug: 197695932
Test: make RunSettingsRoboTests ROBOTEST_FILTER=CaptionPropertiesFragmentTest CaptionTogglePreferenceControllerTest
Change-Id: I7013a7aa284b587c329c2e678dbb079e553ea94d

tests/robotests/src/com/android/settings/accessibility/CaptionPropertiesFragmentTest.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2022 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.settings.accessibility;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import android.content.Context;
+
+import androidx.test.core.app.ApplicationProvider;
+
+import com.android.settings.R;
+import com.android.settings.testutils.XmlTestUtils;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+
+import java.util.List;
+
+/** Tests for {@link CaptionPropertiesFragment}. */
+@RunWith(RobolectricTestRunner.class)
+public class CaptionPropertiesFragmentTest {
+
+    private final Context mContext = ApplicationProvider.getApplicationContext();
+
+    @Test
+    public void getNonIndexableKeys_existInXmlLayout() {
+        final List<String> niks = CaptionPropertiesFragment.SEARCH_INDEX_DATA_PROVIDER
+                .getNonIndexableKeys(mContext);
+        final List<String> keys =
+                XmlTestUtils.getKeysFromPreferenceXml(mContext,
+                        R.xml.captioning_settings);
+
+        assertThat(keys).containsAtLeastElementsIn(niks);
+    }
+}