Make battery status refresh in SettingsActivity

Before this cl, the battery text in SettingsActivity is one time
update, won't refresh based on real battery status.

This cl elicits BatteryBroadcastReceiver from PowerUsageBase and
make it reusable in both SettingsActivity and battery page.

BatteryBroadcastReceiver will invoke callback if:
1. Battery level changed on integer level(100->99)
2. Battery status has changed(i.e. charging)

Bug: 29346753
Test: RunSettingsRoboTests

Change-Id: If522d15a700ccbc8bae24f5712e05ec27ea4cbfa

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

@@ -0,0 +1,95 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.settings.fuelgauge;
+
+import android.content.Context;
+import android.content.Intent;
+import android.os.BatteryManager;
+
+import com.android.settings.SettingsRobolectricTestRunner;
+import com.android.settings.TestConfig;
+import com.android.settings.Utils;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.robolectric.RuntimeEnvironment;
+import org.robolectric.annotation.Config;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+
+@RunWith(SettingsRobolectricTestRunner.class)
+@Config(manifest = TestConfig.MANIFEST_PATH, sdk = TestConfig.SDK_VERSION)
+public class BatteryBroadcastReceiverTest {
+    private static final String BATTERY_INIT_LEVEL = "100%";
+    private static final String BATTERY_INIT_STATUS = "Not charging";
+    private static final int BATTERY_INTENT_LEVEL = 80;
+    private static final int BATTERY_INTENT_SCALE = 100;
+
+    @Mock
+    private BatteryBroadcastReceiver.OnBatteryChangedListener mBatteryListener;
+    private BatteryBroadcastReceiver mBatteryBroadcastReceiver;
+    private Context mContext;
+    private Intent mChargingIntent;
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        mContext = RuntimeEnvironment.application;
+
+        mBatteryBroadcastReceiver = new BatteryBroadcastReceiver(mContext);
+        mBatteryBroadcastReceiver.mBatteryLevel = BATTERY_INIT_LEVEL;
+        mBatteryBroadcastReceiver.mBatteryStatus = BATTERY_INIT_STATUS;
+        mBatteryBroadcastReceiver.setBatteryChangedListener(mBatteryListener);
+
+        mChargingIntent = new Intent(Intent.ACTION_BATTERY_CHANGED);
+        mChargingIntent.putExtra(BatteryManager.EXTRA_LEVEL, BATTERY_INTENT_LEVEL);
+        mChargingIntent.putExtra(BatteryManager.EXTRA_SCALE, BATTERY_INTENT_SCALE);
+        mChargingIntent.putExtra(BatteryManager.EXTRA_STATUS,
+                BatteryManager.BATTERY_STATUS_CHARGING);
+    }
+
+    @Test
+    public void testOnReceive_batteryDataChanged_dataUpdated() {
+        mBatteryBroadcastReceiver.onReceive(mContext, mChargingIntent);
+
+        assertThat(mBatteryBroadcastReceiver.mBatteryLevel).isEqualTo(
+                Utils.getBatteryPercentage(mChargingIntent));
+        assertThat(mBatteryBroadcastReceiver.mBatteryStatus).isEqualTo(
+                Utils.getBatteryStatus(mContext.getResources(), mChargingIntent));
+        verify(mBatteryListener).onBatteryChanged();
+    }
+
+    @Test
+    public void testOnReceive_batteryDataNotChanged_listenerNotInvoked() {
+        final String batteryLevel = Utils.getBatteryPercentage(mChargingIntent);
+        final String batteryStatus = Utils.getBatteryStatus(mContext.getResources(),
+                mChargingIntent);
+        mBatteryBroadcastReceiver.mBatteryLevel = batteryLevel;
+        mBatteryBroadcastReceiver.mBatteryStatus = batteryStatus;
+
+        mBatteryBroadcastReceiver.onReceive(mContext, mChargingIntent);
+
+        assertThat(mBatteryBroadcastReceiver.mBatteryLevel).isEqualTo(batteryLevel);
+        assertThat(mBatteryBroadcastReceiver.mBatteryStatus).isEqualTo(batteryStatus);
+        verify(mBatteryListener, never()).onBatteryChanged();
+    }
+
+}