New feature “Text and reading options” for SetupWizard, Wallpaper, and Settings (12/n).

- Link-up between the preview, font size, and display size preferences.
- Add the preview preference and entry.

Bug: 211503117
Test: make RunSettingsRoboTests ROBOTEST_FILTER=TextReadingPreviewControllerTest
Test: make RunSettingsRoboTests ROBOTEST_FILTER=TextReadingPreviewPreferenceTest
Change-Id: Ic6c48861a0051670fd78b13dca5488711de30cb8

src/com/android/settings/accessibility/TextReadingPreviewPreference.java

@@ -32,8 +32,9 @@ import com.android.settings.widget.DotsPageIndicator;
 /**
  * A {@link Preference} that could show the preview related to the text and reading options.
  */
-final class TextReadingPreviewPreference extends Preference {
+public class TextReadingPreviewPreference extends Preference {
     private int mCurrentItem;
+    private int mLastLayerIndex;
     private PreviewPagerAdapter mPreviewAdapter;
 
     TextReadingPreviewPreference(Context context) {
@@ -41,7 +42,7 @@ final class TextReadingPreviewPreference extends Preference {
         init();
     }
 
-    TextReadingPreviewPreference(Context context, AttributeSet attrs) {
+    public TextReadingPreviewPreference(Context context, AttributeSet attrs) {
         super(context, attrs);
         init();
     }
@@ -120,4 +121,16 @@ final class TextReadingPreviewPreference extends Preference {
     private void init() {
         setLayoutResource(R.layout.accessibility_text_reading_preview);
     }
+
+    void notifyPreviewPagerChanged(int pagerIndex) {
+        Preconditions.checkNotNull(mPreviewAdapter,
+                "Preview adapter is null, you should init the preview adapter first");
+
+        if (pagerIndex != mLastLayerIndex) {
+            mPreviewAdapter.setPreviewLayer(pagerIndex, mLastLayerIndex, getCurrentItem(),
+                    /* animate= */ false);
+        }
+
+        mLastLayerIndex = pagerIndex;
+    }
 }