Fix flicker in SIM card page

Before fix, the DefaultSubscriptionController will set an empty summary
before data is ready.

Not set the summary before data is ready to fix.

Also fix the ignored tests.

Fix: 277301125
Test: Manual on Mobile Settings
Test: Unit test
Change-Id: I07d964b9f9ce21f8f168cb775eea188e48172c5d

src/com/android/settings/network/telephony/DefaultSubscriptionController.java

@@ -112,6 +112,8 @@ public abstract class DefaultSubscriptionController extends TelephonyBasePrefere
     public void displayPreference(PreferenceScreen screen) {
         super.displayPreference(screen);
         mPreference = screen.findPreference(getPreferenceKey());
+        // Set a summary placeholder to reduce flicker.
+        mPreference.setSummaryProvider(pref -> mContext.getString(R.string.summary_placeholder));
         updateEntries();
     }
 
@@ -120,7 +122,7 @@ public abstract class DefaultSubscriptionController extends TelephonyBasePrefere
         // Currently, cannot use ListPreference.setSummary() when the summary contains user
         // generated string, because ListPreference.getSummary() is using String.format() to format
         // the summary when the summary is set by ListPreference.setSummary().
-        if (preference != null) {
+        if (preference != null && !mSubInfoEntityList.isEmpty()) {
             preference.setSummaryProvider(pref -> getSummary());
         }
     }
@@ -146,6 +148,7 @@ public abstract class DefaultSubscriptionController extends TelephonyBasePrefere
         final ArrayList<CharSequence> displayNames = new ArrayList<>();
         final ArrayList<CharSequence> subscriptionIds = new ArrayList<>();
         List<SubscriptionInfoEntity> list = getSubscriptionInfoList();
+        if (list.isEmpty()) return;
 
         if (list.size() == 1) {
             mPreference.setEnabled(false);