Move load battery consumer icon and label into the background

move high latency icon and label loading into the background thread to
improve the performance and first frame response time, which is also the
pre-work for checking whether a item is tappable or not feature (will
work this on the next patch)

Bug: 188751551
Test: make SettingsgRoboTests
Change-Id: I4e5712e995fce055d2735135c28be60fb70e5796

src/com/android/settings/fuelgauge/BatteryChartPreferenceController.java

@@ -20,6 +20,7 @@ import android.app.settings.SettingsEnums;
 import android.content.Context;
 import android.content.res.Configuration;
 import android.graphics.drawable.Drawable;
+import android.os.AsyncTask;
 import android.os.Bundle;
 import android.os.Handler;
 import android.os.Looper;
@@ -64,7 +65,6 @@ public class BatteryChartPreferenceController extends AbstractPreferenceControll
                 ExpandDividerPreference.OnExpandListener {
     private static final String TAG = "BatteryChartPreferenceController";
     private static final String KEY_FOOTER_PREF = "battery_graph_footer";
-    private static final int ADD_FOOTER_DELAYED_MS = 250;
 
     /** Desired battery history size for timestamp slots. */
     public static final int DESIRED_HISTORY_SIZE = 25;
@@ -267,11 +267,6 @@ public class BatteryChartPreferenceController extends AbstractPreferenceControll
 
     void setBatteryHistoryMap(
             final Map<Long, Map<String, BatteryHistEntry>> batteryHistoryMap) {
-        mHandler.post(() -> setBatteryHistoryMapInner(batteryHistoryMap));
-    }
-
-    private void setBatteryHistoryMapInner(
-            final Map<Long, Map<String, BatteryHistEntry>> batteryHistoryMap) {
         // Resets all battery history data relative variables.
         if (batteryHistoryMap == null || batteryHistoryMap.isEmpty()) {
             mBatteryIndexedMap = null;
@@ -298,19 +293,15 @@ public class BatteryChartPreferenceController extends AbstractPreferenceControll
             mBatteryHistoryLevels[index] =
                 Math.round(batteryLevelCounter / entryMap.size());
         }
-        // Generates indexed usage map for chart.
-        mBatteryIndexedMap =
-            ConvertUtils.getIndexedUsageMap(
-                mPrefContext, /*timeSlotSize=*/ CHART_LEVEL_ARRAY_SIZE - 1,
-                mBatteryHistoryKeys, batteryHistoryMap,
-                /*purgeLowPercentageAndFakeData=*/ true);
         forceRefreshUi();
-
         Log.d(TAG, String.format(
             "setBatteryHistoryMap() size=%d\nkeys=%s\nlevels=%s",
             batteryHistoryMap.size(),
             utcToLocalTime(mBatteryHistoryKeys),
             Arrays.toString(mBatteryHistoryLevels)));
+
+        // Loads item icon and label in the background.
+        new LoadAllItemsInfoTask(batteryHistoryMap).execute();
     }
 
     void setBatteryChartView(final BatteryChartView batteryChartView) {
@@ -599,9 +590,7 @@ public class BatteryChartPreferenceController extends AbstractPreferenceControll
             containAppItems
                 ? R.string.battery_usage_screen_footer
                 : R.string.battery_usage_screen_footer_empty));
-        mHandler.postDelayed(
-            () -> mPreferenceScreen.addPreference(mFooterPreference),
-            ADD_FOOTER_DELAYED_MS);
+        mHandler.post(() -> mPreferenceScreen.addPreference(mFooterPreference));
     }
 
     private static String utcToLocalTime(long[] timestamps) {
@@ -670,4 +659,53 @@ public class BatteryChartPreferenceController extends AbstractPreferenceControll
         }
         return batteryHistoryKeys;
     }
+
+    // Loads all items icon and label in the background.
+    private final class LoadAllItemsInfoTask
+            extends AsyncTask<Void, Void, Map<Integer, List<BatteryDiffEntry>>> {
+
+        private long[] mBatteryHistoryKeysCache;
+        private Map<Long, Map<String, BatteryHistEntry>> mBatteryHistoryMap;
+
+        private LoadAllItemsInfoTask(
+                Map<Long, Map<String, BatteryHistEntry>> batteryHistoryMap) {
+            this.mBatteryHistoryMap = batteryHistoryMap;
+            this.mBatteryHistoryKeysCache = mBatteryHistoryKeys;
+        }
+
+        @Override
+        protected Map<Integer, List<BatteryDiffEntry>> doInBackground(Void... voids) {
+            if (mPrefContext == null || mBatteryHistoryKeysCache == null) {
+                return null;
+            }
+            final long startTime = System.currentTimeMillis();
+            final Map<Integer, List<BatteryDiffEntry>> indexedUsageMap =
+                ConvertUtils.getIndexedUsageMap(
+                    mPrefContext, /*timeSlotSize=*/ CHART_LEVEL_ARRAY_SIZE - 1,
+                    mBatteryHistoryKeysCache, mBatteryHistoryMap,
+                    /*purgeLowPercentageAndFakeData=*/ true);
+            // Pre-loads each BatteryDiffEntry relative icon and label for all slots.
+            for (List<BatteryDiffEntry> entries : indexedUsageMap.values()) {
+                entries.forEach(entry -> entry.loadLabelAndIcon());
+            }
+            Log.d(TAG, String.format("execute LoadAllItemsInfoTask in %d/ms",
+                (System.currentTimeMillis() - startTime)));
+            return indexedUsageMap;
+        }
+
+        @Override
+        protected void onPostExecute(
+                Map<Integer, List<BatteryDiffEntry>> indexedUsageMap) {
+            mBatteryHistoryMap = null;
+            mBatteryHistoryKeysCache = null;
+            if (indexedUsageMap == null) {
+                return;
+            }
+            // Posts results back to main thread to refresh UI.
+            mHandler.post(() -> {
+                mBatteryIndexedMap = indexedUsageMap;
+                forceRefreshUi();
+            });
+        }
+    }
 }

src/com/android/settings/fuelgauge/BatteryDiffEntry.java

@@ -142,7 +142,7 @@ public class BatteryDiffEntry {
         return false;
     }
 
-    private void loadLabelAndIcon() {
+    void loadLabelAndIcon() {
         if (mIsLoaded) {
             return;
         }