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;
@Override
protected 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);
}
@Override
protected void onStop() {
super.onStop();
unregisterReceiver(receiver);
}
private static class BatteryReceiver extends BroadcastReceiver{
@Override
public 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 Intent
public static final int BATTERY_HEALTH_UNKNOWN = Constants.BATTERY_HEALTH_UNKNOWN; //1
public static final int BATTERY_HEALTH_GOOD = Constants.BATTERY_HEALTH_GOOD; //2
public static final int BATTERY_HEALTH_OVERHEAT = Constants.BATTERY_HEALTH_OVERHEAT; //3
public static final int BATTERY_HEALTH_DEAD = Constants.BATTERY_HEALTH_DEAD; //4
public static final int BATTERY_HEALTH_OVER_VOLTAGE = Constants.BATTERY_HEALTH_OVER_VOLTAGE; // 5
public static final int BATTERY_HEALTH_UNSPECIFIED_FAILURE = Constants.BATTERY_HEALTH_UNSPECIFIED_FAILURE; //6
public 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 Intent
public static final int BATTERY_STATUS_UNKNOWN = Constants.BATTERY_STATUS_UNKNOWN;//1
public static final int BATTERY_STATUS_CHARGING = Constants.BATTERY_STATUS_CHARGING;//2
public static final int BATTERY_STATUS_DISCHARGING = Constants.BATTERY_STATUS_DISCHARGING;//3
public static final int BATTERY_STATUS_NOT_CHARGING = Constants.BATTERY_STATUS_NOT_CHARGING;//4
public 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 ，
<receiver
android: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 exists if (new File("/sys/devices/virtual/switch/invalid_charger/state").exists()) { UEventObserver invalidChargerObserver = new UEventObserver() { @Override public 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"); } } //... @Override public void onStart() { registerHealthCallback(); mBinderService = new BinderService(); publishBinderService("battery", mBinderService); mBatteryPropertiesRegistrar = new BatteryPropertiesRegistrar(); publishBinderService("batteryproperties", mBatteryPropertiesRegistrar); publishLocalService(BatteryManagerInternal.class, new LocalService()); } @Override public 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) { @Override public 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() {
@Override
public 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() {
@Override
public 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() {
@Override
public 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;
@Override
protected 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") {
@Override
public 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() {
@Override
public 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);
}
}
});
}
}