[Settings] Avoid rendering hidden preferences

Under dashboards with expand button, preferences are renderred even
not been expanded.
Avoid from rendering un-expanded preference can improve the performance
of dashboard display.

Bug: 141833767
Test: manual
Change-Id: I00c6f827a0b7b7cec6a6fd8c809b94ca1dce88bb

src/com/android/settings/SettingsPreferenceFragment.java

@@ -258,6 +258,18 @@ public abstract class SettingsPreferenceFragment extends InstrumentedPreferenceF
         return 0;
     }
 
+    /**
+     * Whether preference is allowing to be displayed to the user.
+     *
+     * @param preference to check if it can be displayed to the user (not hidding in expand area).
+     * @return {@code true} when preference is allowing to be displayed to the user.
+     * {@code false} when preference is hidden in expand area and not been displayed to the user.
+     */
+    protected boolean isPreferenceExpanded(Preference preference) {
+        return ((mAdapter == null)
+                || (mAdapter.getPreferenceAdapterPosition(preference) != RecyclerView.NO_POSITION));
+    }
+
     protected void onDataSetChanged() {
         highlightPreferenceIfNeeded();
         updateEmptyView();