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;
}


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