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    Android编程之电池电量信息更新的方法(基于BatteryService实现)

    栏目:win服务器问题汇总 时间:2019-11-10 15:50

    本文实例讲述了Android编程之电池电量信息更新的方法。分享给大家供大家参考,具体如下:

    电池的信息,电压,温度,充电状态等等,都是由BatteryService来提供的。BatteryService是跑在system_process当中,在系统初始化的时候启动,如下

    在SystemServer.java中可以看到启动BatteryService的代码:

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

    1. 数据来源

    BatteryService通过JNI(com_android_server_BatteryService.cpp)读取数据。BatteryService通过JNI注册的不仅有函数,还有变量。 如下:

    //##############在BatteryService.java中声明的变量################
    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中声明的变量,在com_android_server_BatteryService.cpp中共用,即在com_android_server_BatteryService.cpp中其实操作的也是BatteryService.java中声明的变量

    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");
    
    

    上面这些变量的值,对应是从下面的文件中读取的,一只文件存储一个数值。

    #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是运行在Linux内核上面的,/sys/class/power_supply亦是Linux内核下面的目录。至于这些文件时怎么生成的,则是由Platform来控制的。

    2. 数据传送

    电池的这些信息是通过何种方式,被其他应用所获得的。可以想到的有两种方式,第一种,应用主动从BatteryService获得数据;第二种,BatteryService主动把数据传送给所关心的应用程序。

    BatteryService采用的是第二种方式,所有的电池的信息数据是通过Intent传送出去的。在BatteryService.java中,Code如下: