New feature “Text and reading options” for SetupWizard, Wallpaper, and Settings (6/n).

- Create new preview preference.
1) It will be integrated with TextReadingPreferenceFragment, and sub
previews layouts like app launchers, conversation messages, and mail
content.

Bug: 211503117
Test: make -j64 RunSettingsRoboTests ROBOTEST_FILTER=TextReadingPreviewPreferenceTest
Change-Id: I2d82d58438ee3f96c5a8dbb1809a0d6bdf3a00a2

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

@@ -0,0 +1,115 @@
+/*
+ * 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 android.content.res.Configuration;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.widget.LinearLayout;
+
+import androidx.preference.PreferenceViewHolder;
+import androidx.test.core.app.ApplicationProvider;
+import androidx.viewpager.widget.ViewPager;
+
+import com.android.settings.R;
+import com.android.settings.display.PreviewPagerAdapter;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+
+/**
+ * Tests for {@link TextReadingPreferenceFragment}.
+ */
+@RunWith(RobolectricTestRunner.class)
+public class TextReadingPreviewPreferenceTest {
+
+    private TextReadingPreviewPreference mTextReadingPreviewPreference;
+    private PreferenceViewHolder mHolder;
+    private ViewPager mViewPager;
+    private PreviewPagerAdapter mPreviewPagerAdapter;
+
+    @Before
+    public void setUp() {
+        final Context context = ApplicationProvider.getApplicationContext();
+        final int[] sampleResIds = new int[]{1, 2, 3, 4, 5, 6};
+        final Configuration[] configurations = createConfigurations(6);
+        mTextReadingPreviewPreference = new TextReadingPreviewPreference(context);
+        mPreviewPagerAdapter =
+                new PreviewPagerAdapter(context, /* isLayoutRtl= */ false, sampleResIds,
+                        configurations);
+        final LayoutInflater inflater = LayoutInflater.from(context);
+        final View view =
+                inflater.inflate(mTextReadingPreviewPreference.getLayoutResource(),
+                        new LinearLayout(context), false);
+        mHolder = PreferenceViewHolder.createInstanceForTests(view);
+        mViewPager = view.findViewById(R.id.preview_pager);
+    }
+
+    @Test
+    public void setPreviewerAdapter_success() {
+        mTextReadingPreviewPreference.setPreviewAdapter(mPreviewPagerAdapter);
+        mTextReadingPreviewPreference.onBindViewHolder(mHolder);
+
+        assertThat(mViewPager.getAdapter()).isEqualTo(mPreviewPagerAdapter);
+    }
+
+    @Test
+    public void setPreviewAdapterWithNull_resetCurrentItem() {
+        final int currentItem = 2;
+        mTextReadingPreviewPreference.setPreviewAdapter(mPreviewPagerAdapter);
+        mTextReadingPreviewPreference.setCurrentItem(currentItem);
+        mTextReadingPreviewPreference.onBindViewHolder(mHolder);
+
+        mTextReadingPreviewPreference.setPreviewAdapter(null);
+        mTextReadingPreviewPreference.onBindViewHolder(mHolder);
+
+        assertThat(mTextReadingPreviewPreference.getCurrentItem()).isEqualTo(0);
+    }
+
+    @Test
+    public void setCurrentItem_success() {
+        final int currentItem = 3;
+        mTextReadingPreviewPreference.setPreviewAdapter(mPreviewPagerAdapter);
+        mTextReadingPreviewPreference.onBindViewHolder(mHolder);
+
+        mTextReadingPreviewPreference.setCurrentItem(currentItem);
+        mTextReadingPreviewPreference.onBindViewHolder(mHolder);
+
+        assertThat(mViewPager.getCurrentItem()).isEqualTo(currentItem);
+    }
+
+    @Test(expected = NullPointerException.class)
+    public void setCurrentItemBeforeSetPreviewAdapter_throwNPE() {
+        final int currentItem = 5;
+
+        mTextReadingPreviewPreference.setCurrentItem(currentItem);
+    }
+
+    private static Configuration[] createConfigurations(int count) {
+        final Configuration[] configurations = new Configuration[count];
+        for (int i = 0; i < count; i++) {
+            configurations[i] = new Configuration();
+        }
+
+        return configurations;
+    }
+}