Add method to calculate last full charge time

Bug: 38481300
Test: RunSettingsRoboTests
Change-Id: Icd551921f263352eb01d0c6ada62d277c8699507

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

@@ -261,6 +261,19 @@ public class BatteryUtils {
         });
     }
 
+    /**
+     * Calculate the time since last full charge, including the device off time
+     *
+     * @param batteryStatsHelper utility class that contains the data
+     * @param currentTimeMs      current wall time
+     * @return time in millis
+     */
+    public long calculateLastFullChargeTime(BatteryStatsHelper batteryStatsHelper,
+            long currentTimeMs) {
+        return currentTimeMs - batteryStatsHelper.getStats().getStartClockTime();
+
+    }
+
     private long convertUsToMs(long timeUs) {
         return timeUs / 1000;
     }

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

@@ -24,7 +24,6 @@ import android.content.Intent;
 import android.content.IntentFilter;
 import android.content.Loader;
 import android.content.res.TypedArray;
-import android.content.res.Resources;
 import android.database.Cursor;
 import android.graphics.drawable.Drawable;
 import android.net.Uri;
@@ -42,13 +41,11 @@ import android.support.v7.preference.Preference;
 import android.support.v7.preference.PreferenceGroup;
 import android.text.TextUtils;
 import android.text.format.DateUtils;
-import android.text.format.Formatter;
 import android.util.Log;
 import android.util.SparseArray;
 import android.view.Menu;
 import android.view.MenuInflater;
 import android.view.MenuItem;
-import android.widget.TextView;
 
 import com.android.internal.logging.nano.MetricsProto.MetricsEvent;
 import com.android.internal.os.BatterySipper;
@@ -490,12 +487,13 @@ public class PowerUsageSummary extends PowerUsageBase implements
         BatteryInfo batteryInfo = getBatteryInfo(elapsedRealtimeUs, batteryBroadcast);
         mBatteryHeaderPreferenceController.updateHeaderPreference(batteryInfo);
 
-        final long runningTime = mBatteryUtils.calculateRunningTimeBasedOnStatsType(mStatsHelper,
-                mStatsType);
+        final long lastFullChargeTime = mBatteryUtils.calculateLastFullChargeTime(mStatsHelper,
+                System.currentTimeMillis());
         updateScreenPreference();
-        updateLastFullChargePreference(runningTime);
+        updateLastFullChargePreference(lastFullChargeTime);
 
-        final CharSequence timeSequence = Utils.formatElapsedTime(context, runningTime, false);
+        final CharSequence timeSequence = Utils.formatElapsedTime(context, lastFullChargeTime,
+                false);
         final int resId = mShowAllApps ? R.string.power_usage_list_summary_device
                 : R.string.power_usage_list_summary;
         mAppListGroup.setTitle(TextUtils.expandTemplate(getText(resId), timeSequence));

tests/robotests/src/com/android/settings/fuelgauge/BatteryUtilsTest.java

@@ -305,6 +305,16 @@ public class BatteryUtilsTest {
                 mScreenBatterySipper);
     }
 
+    @Test
+    public void testCalculateLastFullChargeTime() {
+        final long currentTimeMs = System.currentTimeMillis();
+        when(mBatteryStatsHelper.getStats().getStartClockTime()).thenReturn(
+                currentTimeMs - TIME_SINCE_LAST_FULL_CHARGE_MS);
+
+        assertThat(mBatteryUtils.calculateLastFullChargeTime(
+                mBatteryStatsHelper, currentTimeMs)).isEqualTo(TIME_SINCE_LAST_FULL_CHARGE_MS);
+    }
+
     private BatterySipper createTestSmearBatterySipper(long activityTime, double totalPowerMah,
             int uidCode, boolean isUidNull) {
         final BatterySipper sipper = mock(BatterySipper.class);