Improve the latency of first entering Apps page

Root cause:
AppsPreferenceController will query the recent app usages twice on
the main thread.

Solution:
Set flag to ensure only triggering refreshUi() once when entering
the Apps page.

Also correct the preference key of apps.xml since we don’t have
duplicated preferences now.

Fixes: 183176038
Test: robotests & visual
Change-Id: Ia41ee1e4a1946b8122deca63e318d3915afcc426

res/xml/apps.xml

@@ -55,7 +55,7 @@
         settings:searchable="false"/>
 
     <Preference
-        android:key="default_apps_v2"
+        android:key="default_apps"
         android:title="@string/app_default_dashboard_title"
         android:order="-996"
         settings:controller="com.android.settings.applications.DefaultAppsPreferenceController">
@@ -85,7 +85,7 @@
     </Preference>
 
     <Preference
-        android:key="special_access_v2"
+        android:key="special_access"
         android:fragment="com.android.settings.applications.specialaccess.SpecialAccessSettings"
         android:title="@string/special_access"
         android:order="20"

src/com/android/settings/applications/AppDashboardFragment.java

@@ -69,6 +69,7 @@ public class AppDashboardFragment extends DashboardFragment {
         use(SpecialAppAccessPreferenceController.class).setSession(getSettingsLifecycle());
         mAppsPreferenceController = use(AppsPreferenceController.class);
         mAppsPreferenceController.setFragment(this /* fragment */);
+        getSettingsLifecycle().addObserver(mAppsPreferenceController);
 
         final HibernatedAppsPreferenceController hibernatedAppsPreferenceController =
                 use(HibernatedAppsPreferenceController.class);

src/com/android/settings/applications/AppsPreferenceController.java

@@ -26,6 +26,9 @@ import android.util.ArrayMap;
 
 import androidx.annotation.VisibleForTesting;
 import androidx.fragment.app.Fragment;
+import androidx.lifecycle.Lifecycle;
+import androidx.lifecycle.LifecycleObserver;
+import androidx.lifecycle.OnLifecycleEvent;
 import androidx.preference.Preference;
 import androidx.preference.PreferenceCategory;
 import androidx.preference.PreferenceScreen;
@@ -45,7 +48,8 @@ import java.util.Map;
  * This controller displays up to four recently used apps.
  * If there is no recently used app, we only show up an "App Info" preference.
  */
-public class AppsPreferenceController extends BasePreferenceController {
+public class AppsPreferenceController extends BasePreferenceController implements
+        LifecycleObserver {
 
     public static final int SHOW_RECENT_APP_COUNT = 4;
 
@@ -73,6 +77,7 @@ public class AppsPreferenceController extends BasePreferenceController {
     Preference mSeeAllPref;
 
     private Fragment mHost;
+    private boolean mInitialLaunch = false;
 
     public AppsPreferenceController(Context context) {
         super(context, KEY_RECENT_APPS_CATEGORY);
@@ -95,13 +100,24 @@ public class AppsPreferenceController extends BasePreferenceController {
         super.displayPreference(screen);
         initPreferences(screen);
         refreshUi();
+        mInitialLaunch = true;
     }
 
     @Override
     public void updateState(Preference preference) {
         super.updateState(preference);
+        if (!mInitialLaunch) {
             refreshUi();
         }
+    }
+
+    /**
+     * Called when the apps page pauses.
+     */
+    @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
+    public void onPause() {
+        mInitialLaunch = false;
+    }
 
     @VisibleForTesting
     void refreshUi() {
@@ -109,11 +125,15 @@ public class AppsPreferenceController extends BasePreferenceController {
         mRecentApps = loadRecentApps();
         if (!mRecentApps.isEmpty()) {
             displayRecentApps();
+            mAllAppsInfoPref.setVisible(false);
             mRecentAppsCategory.setVisible(true);
             mGeneralCategory.setVisible(true);
             mSeeAllPref.setVisible(true);
         } else {
             mAllAppsInfoPref.setVisible(true);
+            mRecentAppsCategory.setVisible(false);
+            mGeneralCategory.setVisible(false);
+            mSeeAllPref.setVisible(false);
         }
     }