Apply a new icon cache mechanism for memory improvement

- Avoid loading all app icons at once to decrease memory usage.
- Only load visible icons when entering the apps page.
- Reserve icon placeholder to alleviate icon loading flicker.
- Release icon cache when low memory or leaving apps page.

Bug: 187118427
Bug: 209898662
Test: manual check the smoothness and memory usage of apps pages.
Change-Id: Ifc3c2a73cc88d6e42739df4e8208445afa12e0ea

src/com/android/settings/datausage/UnrestrictedDataAccess.java

@@ -25,6 +25,7 @@ import android.view.View;
 import com.android.settings.R;
 import com.android.settings.dashboard.DashboardFragment;
 import com.android.settings.search.BaseSearchIndexProvider;
+import com.android.settingslib.applications.AppIconCacheManager;
 import com.android.settingslib.applications.ApplicationsState;
 import com.android.settingslib.applications.ApplicationsState.AppFilter;
 import com.android.settingslib.search.SearchIndexable;
@@ -112,6 +113,12 @@ public class UnrestrictedDataAccess extends DashboardFragment {
         return R.xml.unrestricted_data_access_settings;
     }
 
+    @Override
+    public void onDestroyView() {
+        super.onDestroyView();
+        AppIconCacheManager.getInstance().release();
+    }
+
     public static final BaseSearchIndexProvider SEARCH_INDEX_DATA_PROVIDER =
             new BaseSearchIndexProvider(R.xml.unrestricted_data_access_settings);
 }