Workarounds to avoid removing all prefs

Removing all prefs causes ugly animations, so avoid it at all cost
and cache all the prefs (while still added) as long as possible.

Bug: 26271353
Change-Id: I33b84d751938b460f4b66c0158057407dd45d974

src/com/android/settings/SettingsPreferenceFragment.java

@@ -34,6 +34,7 @@ import android.support.v7.preference.PreferenceViewHolder;
 import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.RecyclerView;
 import android.text.TextUtils;
+import android.util.ArrayMap;
 import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.Menu;
@@ -97,6 +98,7 @@ public abstract class SettingsPreferenceFragment extends InstrumentedPreferenceF
     private View mEmptyView;
     private LinearLayoutManager mLayoutManager;
     private HighlightablePreferenceGroupAdapter mAdapter;
+    private ArrayMap<String, Preference> mPreferenceCache;
 
     @Override
     public void onCreate(Bundle icicle) {
@@ -367,6 +369,28 @@ public abstract class SettingsPreferenceFragment extends InstrumentedPreferenceF
         return mAdapter;
     }
 
+    protected void cacheRemoveAllPrefs(PreferenceGroup group) {
+        mPreferenceCache = new ArrayMap<String, Preference>();
+        final int N = group.getPreferenceCount();
+        for (int i = 0; i < N; i++) {
+            Preference p = group.getPreference(i);
+            if (TextUtils.isEmpty(p.getKey())) {
+                continue;
+            }
+            mPreferenceCache.put(p.getKey(), p);
+        }
+    }
+
+    protected Preference getCachedPreference(String key) {
+        return mPreferenceCache != null ? mPreferenceCache.remove(key) : null;
+    }
+
+    protected void removeCachedPrefs(PreferenceGroup group) {
+        for (Preference p : mPreferenceCache.values()) {
+            group.removePreference(p);
+        }
+    }
+
     private void highlightPreference(String key) {
         final int position = canUseListViewForHighLighting(key);
         if (position >= 0) {