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);
 }

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

@@ -16,6 +16,7 @@ package com.android.settings.datausage;
 import static com.android.settingslib.RestrictedLockUtilsInternal.checkIfMeteredDataRestricted;
 
 import android.content.Context;
+import android.graphics.drawable.Drawable;
 import android.os.UserHandle;
 import android.view.View;
 
@@ -26,8 +27,10 @@ import com.android.settings.applications.appinfo.AppInfoDashboardFragment;
 import com.android.settings.dashboard.DashboardFragment;
 import com.android.settingslib.RestrictedLockUtils.EnforcedAdmin;
 import com.android.settingslib.RestrictedPreferenceHelper;
+import com.android.settingslib.applications.AppUtils;
 import com.android.settingslib.applications.ApplicationsState;
 import com.android.settingslib.applications.ApplicationsState.AppEntry;
+import com.android.settingslib.utils.ThreadUtils;
 import com.android.settingslib.widget.AppSwitchPreference;
 
 public class UnrestrictedDataAccessPreference extends AppSwitchPreference implements
@@ -39,6 +42,7 @@ public class UnrestrictedDataAccessPreference extends AppSwitchPreference implem
     private final DataSaverBackend mDataSaverBackend;
     private final DashboardFragment mParentFragment;
     private final RestrictedPreferenceHelper mHelper;
+    private Drawable mCacheIcon;
 
     public UnrestrictedDataAccessPreference(final Context context, AppEntry entry,
             ApplicationsState applicationsState, DataSaverBackend dataSaverBackend,
@@ -56,8 +60,13 @@ public class UnrestrictedDataAccessPreference extends AppSwitchPreference implem
                 UserHandle.getUserId(entry.info.uid)));
         updateState();
         setKey(generateKey(mEntry));
-        if (mEntry.icon != null) {
-            setIcon(mEntry.icon);
+
+        mCacheIcon = AppUtils.getIconFromCache(mEntry);
+        if (mCacheIcon != null) {
+            setIcon(mCacheIcon);
+        } else {
+            // Set empty icon as default.
+            setIcon(R.drawable.empty_icon);
         }
     }
 
@@ -101,16 +110,13 @@ public class UnrestrictedDataAccessPreference extends AppSwitchPreference implem
 
     @Override
     public void onBindViewHolder(PreferenceViewHolder holder) {
-        if (mEntry.icon == null) {
-            holder.itemView.post(new Runnable() {
-                @Override
-                public void run() {
-                    // Ensure we have an icon before binding.
-                    mApplicationsState.ensureIcon(mEntry);
-                    // This might trigger us to bind again, but it gives an easy way to only
-                    // load the icon once its needed, so its probably worth it.
-                    setIcon(mEntry.icon);
-                }
+        if (mCacheIcon == null) {
+            ThreadUtils.postOnBackgroundThread(() -> {
+                final Drawable icon = AppUtils.getIcon(getContext(), mEntry);
+                ThreadUtils.postOnMainThread(() -> {
+                    setIcon(icon);
+                    mCacheIcon = icon;
+                });
             });
         }
         final boolean disabledByAdmin = isDisabledByAdmin();

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

@@ -29,6 +29,7 @@ import com.android.settings.applications.AppStateBaseBridge;
 import com.android.settings.core.BasePreferenceController;
 import com.android.settings.dashboard.DashboardFragment;
 import com.android.settings.overlay.FeatureFactory;
+import com.android.settingslib.applications.AppUtils;
 import com.android.settingslib.applications.ApplicationsState;
 import com.android.settingslib.applications.ApplicationsState.AppEntry;
 import com.android.settingslib.applications.ApplicationsState.AppFilter;
@@ -125,6 +126,10 @@ public class UnrestrictedDataAccessPreferenceController extends BasePreferenceCo
             return;
         }
 
+        // Preload top visible icons of app list.
+        AppUtils.preloadTopIcons(mContext, apps,
+                mContext.getResources().getInteger(R.integer.config_num_visible_app_icons));
+
         // Create apps key set for removing useless preferences
         final Set<String> appsKeySet = new TreeSet<>();
         // Add or update preferences