andjroid5.1 BatteryManager深入分析



BatteryManager主要是去主动查看电池状态，主要通过binder通信去healthd中查看电池的各个属性。

可以看下BatteryManager的主要代码

    private long queryProperty(int id) {        long ret;        if (mBatteryPropertiesRegistrar == null) {            IBinder b = ServiceManager.getService("batteryproperties");//这个service就是在healthd中加入ServiceManager中            mBatteryPropertiesRegistrar =                IBatteryPropertiesRegistrar.Stub.asInterface(b);//转化接口            if (mBatteryPropertiesRegistrar == null)                return Long.MIN_VALUE;        }        try {            BatteryProperty prop = new BatteryProperty();//新建一个数据类型            if (mBatteryPropertiesRegistrar.getProperty(id, prop) == 0)//prop作为结果返回                ret = prop.getLong();            else                ret = Long.MIN_VALUE;        } catch (RemoteException e) {            ret = Long.MIN_VALUE;        }        return ret;    }    public int getIntProperty(int id) {        return (int)queryProperty(id);    }    public long getLongProperty(int id) {        return queryProperty(id);    }}

接下来我们看下healthd中batteryproperties这个service：

void BatteryPropertiesRegistrar::publish() {    defaultServiceManager()->addService(String16("batteryproperties"), this);//将service加入到serviceManager中}void BatteryPropertiesRegistrar::notifyListeners(struct BatteryProperties props) {    Mutex::Autolock _l(mRegistrationLock);    for (size_t i = 0; i < mListeners.size(); i++) {//通知各个注册到healthd中的listener，类似BatteryService中注册到healthd中的listener（binder通信）        mListeners[i]->batteryPropertiesChanged(props);    }}void BatteryPropertiesRegistrar::registerListener(const sp<IBatteryPropertiesListener>& listener) {//注册到healthd的函数，比如BatteryService中，实现一个aidl，然后将这个类的stub实现，发到这边注册//这样BatteryService中的BatteryLIstener就类似这边的一个server端，把接口发过来，到时候利用notifyListener来进行跨进程调用。    {        if (listener == NULL)            return;        Mutex::Autolock _l(mRegistrationLock);        // check whether this is a duplicate        for (size_t i = 0; i < mListeners.size(); i++) {            if (mListeners[i]->asBinder() == listener->asBinder()) {                return;            }        }        mListeners.add(listener);        listener->asBinder()->linkToDeath(this);    }    healthd_battery_update();}status_t BatteryPropertiesRegistrar::getProperty(int id, struct BatteryProperty *val) {    return healthd_get_property(id, val);}

当BatteryManager中调用getProperty会到healthd中的getProperty，下面我们再详细看看这个函数:

status_t BatteryMonitor::getProperty(int id, struct BatteryProperty *val) {    status_t ret = BAD_VALUE;    val->valueInt64 = LONG_MIN;    switch(id) {    case BATTERY_PROP_CHARGE_COUNTER:        if (!mHealthdConfig->batteryChargeCounterPath.isEmpty()) {            val->valueInt64 =                getIntField(mHealthdConfig->batteryChargeCounterPath);//将结果返回到BatteryProperty对象中            ret = NO_ERROR;//返回0是没有错        } else {            ret = NAME_NOT_FOUND;        }        break;    case BATTERY_PROP_CURRENT_NOW:        if (!mHealthdConfig->batteryCurrentNowPath.isEmpty()) {            val->valueInt64 =                getIntField(mHealthdConfig->batteryCurrentNowPath);            ret = NO_ERROR;        } else {            ret = NAME_NOT_FOUND;        }        break;    case BATTERY_PROP_CURRENT_AVG:        if (!mHealthdConfig->batteryCurrentAvgPath.isEmpty()) {            val->valueInt64 =                getIntField(mHealthdConfig->batteryCurrentAvgPath);            ret = NO_ERROR;        } else {            ret = NAME_NOT_FOUND;        }        break;    case BATTERY_PROP_CAPACITY:        if (!mHealthdConfig->batteryCapacityPath.isEmpty()) {            val->valueInt64 =                getIntField(mHealthdConfig->batteryCapacityPath);            ret = NO_ERROR;        } else {            ret = NAME_NOT_FOUND;        }        break;    case BATTERY_PROP_ENERGY_COUNTER:        if (mHealthdConfig->energyCounter) {            ret = mHealthdConfig->energyCounter(&val->valueInt64);        } else {            ret = NAME_NOT_FOUND;        }        break;    default:        break;    }    return ret;}