[Wi-Fi] Fix TalkBack focus lost in SavedAccessPointsWifiSettings2

PreferenceGroup in a controller is not in a RecyclerView,
TalkBack loses focus after PreferenceGroup#removeAll.

To fix it, only add/remove the preference if it's necessary.

Bug: 153278854
Test: make RunSettingsRoboTests ROBOTEST_FILTER=SavedAccessPointsPreferenceController2Test
Change-Id: Ie9ad5481c33865dce2b7db04d0f969b1f49b80e1

src/com/android/settings/wifi/savedaccesspoints2/SavedAccessPointsPreferenceController2.java

@@ -17,6 +17,7 @@
 package com.android.settings.wifi.savedaccesspoints2;
 
 import android.content.Context;
+import android.text.TextUtils;
 
 import androidx.annotation.VisibleForTesting;
 import androidx.preference.Preference;
@@ -83,14 +84,35 @@ public class SavedAccessPointsPreferenceController2 extends BasePreferenceContro
         return false;
     }
 
+    /**
+     * mPreferenceGroup is not in a RecyclerView. To keep TalkBack focus, this method should not
+     * mPreferenceGroup.removeAll() then mPreferenceGroup.addPreference for mWifiEntries.
+     */
     private void updatePreference() {
-        mPreferenceGroup.removeAll();
-        for (WifiEntry wifiEntry : mWifiEntries) {
-            final WifiEntryPreference preference = new WifiEntryPreference(mContext, wifiEntry);
-            preference.setKey(wifiEntry.getKey());
-            preference.setOnPreferenceClickListener(this);
+        // Remove the Preference of removed WifiEntry.
+        final List<String> removedPreferenceKeys = new ArrayList<>();
+        final int preferenceCount = mPreferenceGroup.getPreferenceCount();
+        for (int i = 0; i < preferenceCount; i++) {
+            final String key = mPreferenceGroup.getPreference(i).getKey();
+            if (mWifiEntries.stream().filter(wifiEntry ->
+                    TextUtils.equals(key, wifiEntry.getKey())).count() == 0) {
+                removedPreferenceKeys.add(key);
+            }
+        }
+        for (String removedPreferenceKey : removedPreferenceKeys) {
+            mPreferenceGroup.removePreference(
+                    mPreferenceGroup.findPreference(removedPreferenceKey));
+        }
 
-            mPreferenceGroup.addPreference(preference);
+        // Add the Preference of new added WifiEntry.
+        for (WifiEntry wifiEntry : mWifiEntries) {
+            if (mPreferenceGroup.findPreference(wifiEntry.getKey()) == null) {
+                final WifiEntryPreference preference = new WifiEntryPreference(mContext, wifiEntry);
+                preference.setKey(wifiEntry.getKey());
+                preference.setOnPreferenceClickListener(this);
+
+                mPreferenceGroup.addPreference(preference);
+            }
         }
     }
 }

tests/robotests/src/com/android/settings/wifi/savedaccesspoints2/SavedAccessPointsPreferenceController2Test.java

@@ -103,4 +103,20 @@ public class SavedAccessPointsPreferenceController2Test {
         assertThat(prefs.size()).isEqualTo(1);
         assertThat(prefs.get(0).getTitle()).isEqualTo(title);
     }
+
+    @Test
+    public void displayPreference_noAccessPoint_shouldRemoveIt() {
+        final String title = "ssid_title";
+        final String key = "key";
+        final WifiEntry mockWifiEntry = mock(WifiEntry.class);
+        when(mockWifiEntry.getTitle()).thenReturn(title);
+        when(mockWifiEntry.getKey()).thenReturn(key);
+        final WifiEntryPreference preference = new WifiEntryPreference(mContext, mockWifiEntry);
+        preference.setKey(key);
+        mPreferenceCategory.addPreference(preference);
+
+        mController.displayPreference(mPreferenceScreen, new ArrayList<>());
+
+        assertThat(mPreferenceCategory.getPreferenceCount()).isEqualTo(0);
+    }
 }