当需要监控系统电量时，用 BatteryManager 来实现。
参考官网 监控电池电量和充电状态
获取电池信息
通过监听 Intent.ACTION_BATTERY_CHANGED 广播实现，在广播接收器中获取电池信息。
这是个粘性广播，即使过了广播发出的时间点后再注册广播接收器，也可以收到上一个广播消息。
按照我的 Demo ，没有触发电量变化，直接打开这个页面就可以收到广播。
public class BatteryActivity extends AppCompatActivity {private final static String TAG = BatteryActivity.class.getSimpleName()；private BatteryReceiver receiver;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_battery);Objects.requireNonNull(getSupportActionBar()).setTitle(TAG);receiver = new BatteryReceiver();IntentFilter filter = new IntentFilter();filter.addAction(Intent.ACTION_BATTERY_CHANGED);registerReceiver(receiver, filter);}@Overrideprotected void onStop() {super.onStop();unregisterReceiver(receiver);}private static class BatteryReceiver extends BroadcastReceiver{@Overridepublic void onReceive(Context context, Intent intent) {if (Intent.ACTION_BATTERY_CHANGED.equals(intent.getAction())) {int level = intent.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);int scale = intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1);int temperature = intent.getIntExtra(BatteryManager.EXTRA_TEMPERATURE, 0);int status = intent.getIntExtra(BatteryManager.EXTRA_STATUS, 0);int health = intent.getIntExtra(BatteryManager.EXTRA_HEALTH, 0);int pluggen = intent.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);}}}
}
电量
电量百分比 = 当前电量 / 电池总量
int level = intent.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);
int scale = intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1);
int batteryPct = level * 100 / scale;
电池温度
模拟器获取的值是 250
int temperature = intent.getIntExtra(BatteryManager.EXTRA_TEMPERATURE, 0);
电池健康
int health = intent.getIntExtra(BatteryManager.EXTRA_HEALTH, 0);
使用模拟器测试，
得到
| 电池健康 | 值 |
|---|---|
| Unknown | 1 |
| Good | 2 |
| Overheat | 3 |
| Dead | 4 |
| Overvoltage | 5 |
| Failed | 6 |
看 BatteryManager 源码，
import android.hardware.health.V1_0.Constants;// values for "health" field in the ACTION_BATTERY_CHANGED Intentpublic static final int BATTERY_HEALTH_UNKNOWN = Constants.BATTERY_HEALTH_UNKNOWN; //1public static final int BATTERY_HEALTH_GOOD = Constants.BATTERY_HEALTH_GOOD; //2public static final int BATTERY_HEALTH_OVERHEAT = Constants.BATTERY_HEALTH_OVERHEAT; //3public static final int BATTERY_HEALTH_DEAD = Constants.BATTERY_HEALTH_DEAD; //4public static final int BATTERY_HEALTH_OVER_VOLTAGE = Constants.BATTERY_HEALTH_OVER_VOLTAGE; // 5public static final int BATTERY_HEALTH_UNSPECIFIED_FAILURE = Constants.BATTERY_HEALTH_UNSPECIFIED_FAILURE; //6public static final int BATTERY_HEALTH_COLD = Constants.BATTERY_HEALTH_COLD; // 7
追踪到 frameworks/native/services/batteryservice/include/batteryservice/BatteryServiceConstants.h ，
enum {BATTERY_STATUS_UNKNOWN = 1,BATTERY_STATUS_CHARGING = 2,BATTERY_STATUS_DISCHARGING = 3,BATTERY_STATUS_NOT_CHARGING = 4,BATTERY_STATUS_FULL = 5,
};enum {BATTERY_HEALTH_UNKNOWN = 1,BATTERY_HEALTH_GOOD = 2,BATTERY_HEALTH_OVERHEAT = 3,BATTERY_HEALTH_DEAD = 4,BATTERY_HEALTH_OVER_VOLTAGE = 5,BATTERY_HEALTH_UNSPECIFIED_FAILURE = 6,BATTERY_HEALTH_COLD = 7,
};
电池状态 & 充电类型
电池状态
判断是否在充电，
int status = intent.getIntExtra(BatteryManager.EXTRA_STATUS, 0);
看 BatteryManager 源码，
// values for "status" field in the ACTION_BATTERY_CHANGED Intentpublic static final int BATTERY_STATUS_UNKNOWN = Constants.BATTERY_STATUS_UNKNOWN;//1public static final int BATTERY_STATUS_CHARGING = Constants.BATTERY_STATUS_CHARGING;//2public static final int BATTERY_STATUS_DISCHARGING = Constants.BATTERY_STATUS_DISCHARGING;//3public static final int BATTERY_STATUS_NOT_CHARGING = Constants.BATTERY_STATUS_NOT_CHARGING;//4public static final int BATTERY_STATUS_FULL = Constants.BATTERY_STATUS_FULL;//5
充电类型
判断充电类型， 交流电、USB充电、无线充电。
int pluggen = intent.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);
模拟器测试，None = 0 ，AC charger = 1 。
看 BatteryManager 源码，
// values of the "plugged" field in the ACTION_BATTERY_CHANGED intent.// These must be powers of 2./** Power source is an AC charger. */public static final int BATTERY_PLUGGED_AC = OsProtoEnums.BATTERY_PLUGGED_AC; // = 1/** Power source is a USB port. */public static final int BATTERY_PLUGGED_USB = OsProtoEnums.BATTERY_PLUGGED_USB; // = 2/** Power source is wireless. */public static final int BATTERY_PLUGGED_WIRELESS = OsProtoEnums.BATTERY_PLUGGED_WIRELESS; // = 4
监听低电量
当电池点亮过低、电池电量充足会发出这两个广播。
按照官方建议，在电量低时应停用所有后台更新，此时应用应尽量避免进行后台操作。
/*** Broadcast Action: Indicates low battery condition on the device.* This broadcast corresponds to the "Low battery warning" system dialog.** <p class="note">This is a protected intent that can only be sent* by the system.*/@SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)public static final String ACTION_BATTERY_LOW = "android.intent.action.BATTERY_LOW";/*** Broadcast Action: Indicates the battery is now okay after being low.* This will be sent after {@link #ACTION_BATTERY_LOW} once the battery has* gone back up to an okay state.** <p class="note">This is a protected intent that can only be sent* by the system.*/@SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)public static final String ACTION_BATTERY_OKAY = "android.intent.action.BATTERY_OKAY";
按照官网静态广播的写法，没有接收到 ，
<receiverandroid:name=".battery.BatteryReceiver"android:enabled="true"android:exported="true"><intent-filter><action android:name="android.intent.action.BATTERY_LOW"/><action android:name="android.intent.action.BATTERY_OKAY"/></intent-filter></receiver>
用动态广播的写法可以接收到，
receiver = new BatteryReceiver();
IntentFilter filter = new IntentFilter();
filter.addAction(Intent.ACTION_BATTERY_CHANGED);
filter.addAction(Intent.ACTION_BATTERY_LOW);
filter.addAction(Intent.ACTION_BATTERY_OKAY);
registerReceiver(receiver, filter);
用模拟器测试 ，
电量 15% 触发 Intent.ACTION_BATTERY_LOW ，电量 20% 触发 Intent.ACTION_BATTERY_OKAY 。
BatteryService源码分析
基于安卓11。
源码在 frameworks/base/services/core/java/com/android/server/BatteryService.java ，
对应的阈值都是定义在 frameworks$/base/core/res/res/values/config.xml ， 厂商如需定制就改这里。
初始化
BatteryService 继承 SystemService ，
构造函数中
- 初始化 Handler ；
- 通过 LightsManager 实例化 Led ；
- 获取各个阈值；
- 监测 invalid_charger 。
onStart() 中
- 注册电池健康回调，收到回调消息会调用
update(android.hardware.health.V2_1.HealthInfo info)方法更新电池信息； - 初始化 BatteryPropertiesRegistrar 、BinderService 、LocalService。
onBootPhase(int phase) 中
- 监听 Settings.Global.LOW_POWER_MODE_TRIGGER_LEVEL 的变化，有变化时调用
updateBatteryWarningLevelLocked()方法更新一次电池信息。 - 调用
updateBatteryWarningLevelLocked()方法更新一次电池信息。
public final class BatteryService extends SystemService {//...public BatteryService(Context context) {super(context);mContext = context;mHandler = new Handler(true /*async*/);mLed = new Led(context, getLocalService(LightsManager.class));mBatteryStats = BatteryStatsService.getService();mActivityManagerInternal = LocalServices.getService(ActivityManagerInternal.class);mCriticalBatteryLevel = mContext.getResources().getInteger(com.android.internal.R.integer.config_criticalBatteryWarningLevel);mLowBatteryWarningLevel = mContext.getResources().getInteger(com.android.internal.R.integer.config_lowBatteryWarningLevel);mLowBatteryCloseWarningLevel = mLowBatteryWarningLevel + mContext.getResources().getInteger(com.android.internal.R.integer.config_lowBatteryCloseWarningBump);mShutdownBatteryTemperature = mContext.getResources().getInteger(com.android.internal.R.integer.config_shutdownBatteryTemperature);mBatteryLevelsEventQueue = new ArrayDeque<>();mMetricsLogger = new MetricsLogger();// watch for invalid charger messages if the invalid_charger switch existsif (new File("/sys/devices/virtual/switch/invalid_charger/state").exists()) {UEventObserver invalidChargerObserver = new UEventObserver() {@Overridepublic void onUEvent(UEvent event) {final int invalidCharger = "1".equals(event.get("SWITCH_STATE")) ? 1 : 0;synchronized (mLock) {if (mInvalidCharger != invalidCharger) {mInvalidCharger = invalidCharger;}}}};invalidChargerObserver.startObserving("DEVPATH=/devices/virtual/switch/invalid_charger");}}//...@Overridepublic void onStart() {registerHealthCallback();mBinderService = new BinderService();publishBinderService("battery", mBinderService);mBatteryPropertiesRegistrar = new BatteryPropertiesRegistrar();publishBinderService("batteryproperties", mBatteryPropertiesRegistrar);publishLocalService(BatteryManagerInternal.class, new LocalService());}@Overridepublic void onBootPhase(int phase) {if (phase == PHASE_ACTIVITY_MANAGER_READY) {// check our power situation now that it is safe to display the shutdown dialog.synchronized (mLock) {ContentObserver obs = new ContentObserver(mHandler) {@Overridepublic void onChange(boolean selfChange) {synchronized (mLock) {updateBatteryWarningLevelLocked();}}};final ContentResolver resolver = mContext.getContentResolver();resolver.registerContentObserver(Settings.Global.getUriFor(Settings.Global.LOW_POWER_MODE_TRIGGER_LEVEL),false, obs, UserHandle.USER_ALL);updateBatteryWarningLevelLocked();}}}//...private void updateBatteryWarningLevelLocked() {final ContentResolver resolver = mContext.getContentResolver();int defWarnLevel = mContext.getResources().getInteger(com.android.internal.R.integer.config_lowBatteryWarningLevel);mLowBatteryWarningLevel = Settings.Global.getInt(resolver,Settings.Global.LOW_POWER_MODE_TRIGGER_LEVEL, defWarnLevel);if (mLowBatteryWarningLevel == 0) {mLowBatteryWarningLevel = defWarnLevel;}if (mLowBatteryWarningLevel < mCriticalBatteryLevel) {mLowBatteryWarningLevel = mCriticalBatteryLevel;}mLowBatteryCloseWarningLevel = mLowBatteryWarningLevel + mContext.getResources().getInteger(com.android.internal.R.integer.config_lowBatteryCloseWarningBump);processValuesLocked(true);}private void processValuesLocked(boolean force) {//...shutdownIfNoPowerLocked();shutdownIfOverTempLocked();// ...if (force || (mHealthInfo.batteryStatus != mLastBatteryStatus ||mHealthInfo.batteryHealth != mLastBatteryHealth ||mHealthInfo.batteryPresent != mLastBatteryPresent ||mHealthInfo.batteryLevel != mLastBatteryLevel ||mPlugType != mLastPlugType ||mHealthInfo.batteryVoltage != mLastBatteryVoltage ||mHealthInfo.batteryTemperature != mLastBatteryTemperature ||mHealthInfo.maxChargingCurrent != mLastMaxChargingCurrent ||mHealthInfo.maxChargingVoltage != mLastMaxChargingVoltage ||mHealthInfo.batteryChargeCounter != mLastChargeCounter ||mInvalidCharger != mLastInvalidCharger)) {// ...mLastBatteryStatus = mHealthInfo.batteryStatus;mLastBatteryHealth = mHealthInfo.batteryHealth;mLastBatteryPresent = mHealthInfo.batteryPresent;mLastBatteryLevel = mHealthInfo.batteryLevel;mLastPlugType = mPlugType;mLastBatteryVoltage = mHealthInfo.batteryVoltage;mLastBatteryTemperature = mHealthInfo.batteryTemperature;mLastMaxChargingCurrent = mHealthInfo.maxChargingCurrent;mLastMaxChargingVoltage = mHealthInfo.maxChargingVoltage;mLastChargeCounter = mHealthInfo.batteryChargeCounter;mLastBatteryLevelCritical = mBatteryLevelCritical;mLastInvalidCharger = mInvalidCharger;}}
}
低电量广播
电量 15% 触发 Intent.ACTION_BATTERY_LOW ，电量 20% 触发 Intent.ACTION_BATTERY_OKAY 。
<integer name="config_lowBatteryWarningLevel">15</integer>
<integer name="config_lowBatteryCloseWarningBump">5</integer>
逻辑很清楚，
当电量低于 mLowBatteryWarningLevel 就发出广播 Intent.ACTION_BATTERY_LOW ，
当电量高于 mLowBatteryCloseWarningLevel 就发出广播 Intent.ACTION_BATTERY_OKAY。
private int mLowBatteryWarningLevel;private int mLowBatteryCloseWarningLevel;// ...public BatteryService(Context context) {// ...mLowBatteryWarningLevel = mContext.getResources().getInteger(com.android.internal.R.integer.config_lowBatteryWarningLevel);mLowBatteryCloseWarningLevel = mLowBatteryWarningLevel + mContext.getResources().getInteger(com.android.internal.R.integer.config_lowBatteryCloseWarningBump);// ...}// ...if (shouldSendBatteryLowLocked()) {mSentLowBatteryBroadcast = true;final Intent statusIntent = new Intent(Intent.ACTION_BATTERY_LOW);statusIntent.setFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT);statusIntent.putExtra(BatteryManager.EXTRA_SEQUENCE, mSequence);mHandler.post(new Runnable() {@Overridepublic void run() {mContext.sendBroadcastAsUser(statusIntent, UserHandle.ALL);}});} else if (mSentLowBatteryBroadcast &&mHealthInfo.batteryLevel >= mLowBatteryCloseWarningLevel) {mSentLowBatteryBroadcast = false;final Intent statusIntent = new Intent(Intent.ACTION_BATTERY_OKAY);statusIntent.setFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT);statusIntent.putExtra(BatteryManager.EXTRA_SEQUENCE, mSequence);mHandler.post(new Runnable() {@Overridepublic void run() {mContext.sendBroadcastAsUser(statusIntent, UserHandle.ALL);}});}// ...private boolean shouldSendBatteryLowLocked() {final boolean plugged = mPlugType != BATTERY_PLUGGED_NONE;final boolean oldPlugged = mLastPlugType != BATTERY_PLUGGED_NONE;/* The ACTION_BATTERY_LOW broadcast is sent in these situations:* - is just un-plugged (previously was plugged) and battery level is* less than or equal to WARNING, or* - is not plugged and battery level falls to WARNING boundary* (becomes <= mLowBatteryWarningLevel).*/return !plugged&& mHealthInfo.batteryStatus != BatteryManager.BATTERY_STATUS_UNKNOWN&& mHealthInfo.batteryLevel <= mLowBatteryWarningLevel&& (oldPlugged || mLastBatteryLevel > mLowBatteryWarningLevel);}
超低电量关机
BatteryService.java 里，
//...shutdownIfNoPowerLocked();// ...private boolean shouldShutdownLocked() {if (mHealthInfo2p1.batteryCapacityLevel != BatteryCapacityLevel.UNSUPPORTED) {return (mHealthInfo2p1.batteryCapacityLevel == BatteryCapacityLevel.CRITICAL);}if (mHealthInfo.batteryLevel > 0) {return false;}// Battery-less devices should not shutdown.if (!mHealthInfo.batteryPresent) {return false;}// If battery state is not CHARGING, shutdown.// - If battery present and state == unknown, this is an unexpected error state.// - If level <= 0 and state == full, this is also an unexpected state// - All other states (NOT_CHARGING, DISCHARGING) means it is not charging.return mHealthInfo.batteryStatus != BatteryManager.BATTERY_STATUS_CHARGING;}private void shutdownIfNoPowerLocked() {// shut down gracefully if our battery is critically low and we are not powered.// wait until the system has booted before attempting to display the shutdown dialog.if (shouldShutdownLocked()) {mHandler.post(new Runnable() {@Overridepublic void run() {if (mActivityManagerInternal.isSystemReady()) {Intent intent = new Intent(Intent.ACTION_REQUEST_SHUTDOWN);intent.putExtra(Intent.EXTRA_KEY_CONFIRM, false);intent.putExtra(Intent.EXTRA_REASON,PowerManager.SHUTDOWN_LOW_BATTERY);intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);mContext.startActivityAsUser(intent, UserHandle.CURRENT);}}});}}
电量过低时发出 Intent.ACTION_REQUEST_SHUTDOWN 广播，
由 frameworks/base/core/java/com/android/internal/app/ShutdownActivity.java 处理广播
frameworks/base/core/res/AndroidManifest.xml
<activity android:name="com.android.internal.app.ShutdownActivity"android:permission="android.permission.SHUTDOWN"android:theme="@style/Theme.NoDisplay"android:excludeFromRecents="true"><intent-filter><action android:name="com.android.internal.intent.action.REQUEST_SHUTDOWN" /><category android:name="android.intent.category.DEFAULT" /></intent-filter><intent-filter><action android:name="android.intent.action.REBOOT" /><category android:name="android.intent.category.DEFAULT" /></intent-filter></activity>
frameworks/base/core/java/com/android/internal/app/ShutdownActivity.java
public class ShutdownActivity extends Activity {private static final String TAG = "ShutdownActivity";private boolean mReboot;private boolean mConfirm;private boolean mUserRequested;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);Intent intent = getIntent();mReboot = Intent.ACTION_REBOOT.equals(intent.getAction());mConfirm = intent.getBooleanExtra(Intent.EXTRA_KEY_CONFIRM, false);mUserRequested = intent.getBooleanExtra(Intent.EXTRA_USER_REQUESTED_SHUTDOWN, false);final String reason = mUserRequested? PowerManager.SHUTDOWN_USER_REQUESTED: intent.getStringExtra(Intent.EXTRA_REASON);Slog.i(TAG, "onCreate(): confirm=" + mConfirm);Thread thr = new Thread("ShutdownActivity") {@Overridepublic void run() {IPowerManager pm = IPowerManager.Stub.asInterface(ServiceManager.getService(Context.POWER_SERVICE));try {if (mReboot) {pm.reboot(mConfirm, null, false);} else {pm.shutdown(mConfirm, reason, false);}} catch (RemoteException e) {}}};thr.start();finish();// Wait for us to tell the power manager to shutdown.try {thr.join();} catch (InterruptedException e) {}}
}
高温关机
<integer name="config_shutdownBatteryTemperature">680</integer>
超出这个定义的温度就关机，前文模拟器中获取的温度是 250 ，还是很安全的。
private int mShutdownBatteryTemperature;//...public BatteryService(Context context) {// ...mShutdownBatteryTemperature = mContext.getResources().getInteger(com.android.internal.R.integer.config_shutdownBatteryTemperature);// ...}// ...shutdownIfOverTempLocked();// ...private void shutdownIfOverTempLocked() {// shut down gracefully if temperature is too high (> 68.0C by default)// wait until the system has booted before attempting to display the// shutdown dialog.if (mHealthInfo.batteryTemperature > mShutdownBatteryTemperature) {mHandler.post(new Runnable() {@Overridepublic void run() {if (mActivityManagerInternal.isSystemReady()) {Intent intent = new Intent(Intent.ACTION_REQUEST_SHUTDOWN);intent.putExtra(Intent.EXTRA_KEY_CONFIRM, false);intent.putExtra(Intent.EXTRA_REASON,PowerManager.SHUTDOWN_BATTERY_THERMAL_STATE);intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);mContext.startActivityAsUser(intent, UserHandle.CURRENT);}}});}}
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