本文實(shí)例講述了Android編程之電池電量信息更新的方法。分享給大家供大家參考，具體如下：

電池的信息，電壓，溫度，充電狀態(tài)等等，都是由BatteryService來提供的。BatteryService是跑在system_process當(dāng)中，在系統(tǒng)初始化的時(shí)候啟動(dòng)，如下

在SystemServer.java中可以看到啟動(dòng)BatteryService的代碼：

Log.i(TAG, "Starting Battery Service.");BatteryService battery = new BatteryService(context);ServiceManager.addService("battery", battery);

1. 數(shù)據(jù)來源

BatteryService通過JNI（com_android_server_BatteryService.cpp）讀取數(shù)據(jù)。BatteryService通過JNI注冊(cè)的不僅有函數(shù)，還有變量。 如下：

//##############在BatteryService.java中聲明的變量################private boolean mAcOnline; private boolean mUsbOnline; private int mBatteryStatus; private int mBatteryHealth; private boolean mBatteryPresent; private int mBatteryLevel; private int mBatteryVoltage; private int mBatteryTemperature; private String mBatteryTechnology;

在BatteryService.java中聲明的變量，在com_android_server_BatteryService.cpp中共用，即在com_android_server_BatteryService.cpp中其實(shí)操作的也是BatteryService.java中聲明的變量

gFieldIds.mAcOnline = env->GetFieldID(clazz, "mAcOnline", "Z"); gFieldIds.mUsbOnline = env->GetFieldID(clazz, "mUsbOnline", "Z"); gFieldIds.mBatteryStatus = env->GetFieldID(clazz, "mBatteryStatus", "I"); gFieldIds.mBatteryHealth = env->GetFieldID(clazz, "mBatteryHealth", "I"); gFieldIds.mBatteryPresent = env->GetFieldID(clazz, "mBatteryPresent", "Z"); gFieldIds.mBatteryLevel = env->GetFieldID(clazz, "mBatteryLevel", "I"); gFieldIds.mBatteryTechnology = env->GetFieldID(clazz, "mBatteryTechnology", "Ljava/lang/String;"); gFieldIds.mBatteryVoltage = env->GetFieldID(clazz, "mBatteryVoltage", "I"); gFieldIds.mBatteryTemperature = env->GetFieldID(clazz, "mBatteryTemperature", "I");

上面這些變量的值，對(duì)應(yīng)是從下面的文件中讀取的，一只文件存儲(chǔ)一個(gè)數(shù)值。

#define AC_ONLINE_PATH "/sys/class/power_supply/ac/online" #define USB_ONLINE_PATH "/sys/class/power_supply/usb/online" #define BATTERY_STATUS_PATH "/sys/class/power_supply/battery/status" #define BATTERY_HEALTH_PATH "/sys/class/power_supply/battery/health" #define BATTERY_PRESENT_PATH "/sys/class/power_supply/battery/present" #define BATTERY_CAPACITY_PATH "/sys/class/power_supply/battery/capacity" #define BATTERY_VOLTAGE_PATH "/sys/class/power_supply/battery/batt_vol" #define BATTERY_TEMPERATURE_PATH "/sys/class/power_supply/battery/batt_temp" #define BATTERY_TECHNOLOGY_PATH "/sys/class/power_supply/battery/technology"

Android是運(yùn)行在Linux內(nèi)核上面的，/sys/class/power_supply亦是Linux內(nèi)核下面的目錄。至于這些文件時(shí)怎么生成的，則是由Platform來控制的。

2. 數(shù)據(jù)傳送

電池的這些信息是通過何種方式，被其他應(yīng)用所獲得的。可以想到的有兩種方式，第一種，應(yīng)用主動(dòng)從BatteryService獲得數(shù)據(jù)；第二種，BatteryService主動(dòng)把數(shù)據(jù)傳送給所關(guān)心的應(yīng)用程序。

BatteryService采用的是第二種方式，所有的電池的信息數(shù)據(jù)是通過Intent傳送出去的。在BatteryService.java中，Code如下：