一台设备可以有多张SIM卡，最典型的例子就是眼下流行的“双卡双待”。每一张SIM卡都对应一个Subscription，找不到对应的中文术语，我们求助下翻译软件。
Subscription：谷歌翻译为“订阅”，依旧不明觉厉；继续翻译：
订阅（Subscription）：定义了请求者与业务或业务操作之间的关联关系。只有定义了订阅关系，才能通过业务策略，控制请求者对某个业务的访问行为。
我们用谁家的SIM卡就相当于订阅(Subscription)谁家的业务，对应的SIM卡的信息就是Subscription Information，比如运营商名称、MNC、MCC等，多张SIM卡就有多个Subscription Information。
在Android中，针对上述功能的实现、管理就是SubscriptionManager，表现到软件上就是：
各个类的实现比较简单自行参看源码。
SubscriptionManager作用有三个：
获取Subscription信息 更改Subscription某些信息 提供OnSubscriptionsChangedListener监听器，方便其他应用监听Subscription的状态改变是时候看下Subscription了。
Subscription内容：
public class SubscriptionInfo implements Parcelable { /** * Subscription Identifier, this is a device unique number * and not an index into an array */ private int mId; /** * The GID for a SIM that maybe associated with this subscription, empty if unknown */ private String mIccId; /** * The index of the slot that currently contains the subscription * and not necessarily unique and maybe INVALID_SLOT_ID if unknown */ private int mSimSlotIndex; /** * The name displayed to the user that identifies this subscription */ private CharSequence mDisplayName; /** * String that identifies SPN/PLMN * TODO : Add a new field that identifies only SPN for a sim */ private CharSequence mCarrierName; /** * The source of the name, NAME_SOURCE_UNDEFINED, NAME_SOURCE_DEFAULT_SOURCE, * NAME_SOURCE_SIM_SOURCE or NAME_SOURCE_USER_INPUT. */ private int mNameSource; /** * A number presented to the user identify this subscription */ private String mNumber; /** * Data roaming state, DATA_RAOMING_ENABLE, DATA_RAOMING_DISABLE */ private int mDataRoaming; /** * Mobile Country Code */ private int mMcc; /** * Mobile Network Code */ private int mMnc; /** * ISO Country code for the subscription's provider */ private String mCountryIso; }一条Log：
SubscriptionController: [getSubInfoRecord] id:2 iccid:898600020XXXXXXXXXXX simSlotIndex:0 displayName:中国移动 carrierName:No service. nameSource:0 iconTint:-16746133 dataRoaming:0 mcc:460 mnc:2 countIso:cn
看下对应的术语：
ICCID：Integrate circuit card identity 集成电路卡识别码（固化在手机SIM卡中）。ICCID为IC卡的唯一识别号码，共有20位数字组成：
PLMN：Public Land Mobile Network 公共陆地移动网，一般某个国家的一个运营商对应一个PLMN
SPN：Service Provider Name 运营商名称
MCC：Mobile Country Code，移动国家码，MCC的资源由国际电联（ITU）统一分配和管理，唯一识别移动用户所属的国家，共3位，中国为460
MNC：Mobile Network Code 移动网络号码，用于识别移动用户所归属的移动通信网，2~3位数字组成，如中国移动系统使用00、02、04、07，中国联通GSM系统使用01、06、09
ISO country code: 国际上不同国家的ISO编码，比如我们国家：
那么问题来了，这些信息从哪来？
对于SubscriptionController来说，它是从数据库telephony.db的siminfo表中读取：
/data/data/com.android.providers.telephony/databases
siminfo表的创建：
TelephonyProvider.java (g:\rk3288-android6.0f\packages\providers\telephonyprovider\src\com\android\providers\telephony) 105530 2017-04-24 private void createSimInfoTable(SQLiteDatabase db) { db.execSQL("CREATE TABLE " + SIMINFO_TABLE + "(" + SubscriptionManager.UNIQUE_KEY_SUBSCRIPTION_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," + SubscriptionManager.ICC_ID + " TEXT NOT NULL," + SubscriptionManager.SIM_SLOT_INDEX + " INTEGER DEFAULT " + SubscriptionManager.SIM_NOT_INSERTED + "," + SubscriptionManager.DISPLAY_NAME + " TEXT," + SubscriptionManager.CARRIER_NAME + " TEXT," + SubscriptionManager.NAME_SOURCE + " INTEGER DEFAULT " + SubscriptionManager.NAME_SOURCE_DEFAULT_SOURCE + "," + SubscriptionManager.COLOR + " INTEGER DEFAULT " + SubscriptionManager.COLOR_DEFAULT + "," + SubscriptionManager.NUMBER + " TEXT," + SubscriptionManager.DISPLAY_NUMBER_FORMAT + " INTEGER NOT NULL DEFAULT " + SubscriptionManager.DISPLAY_NUMBER_DEFAULT + "," + SubscriptionManager.DATA_ROAMING + " INTEGER DEFAULT " + SubscriptionManager.DATA_ROAMING_DEFAULT + "," + SubscriptionManager.MCC + " INTEGER DEFAULT 0," + SubscriptionManager.MNC + " INTEGER DEFAULT 0," + SubscriptionManager.CB_EXTREME_THREAT_ALERT + " INTEGER DEFAULT 1," + SubscriptionManager.CB_SEVERE_THREAT_ALERT + " INTEGER DEFAULT 1," + SubscriptionManager.CB_AMBER_ALERT + " INTEGER DEFAULT 1," + SubscriptionManager.CB_EMERGENCY_ALERT + " INTEGER DEFAULT 1," + SubscriptionManager.CB_ALERT_SOUND_DURATION + " INTEGER DEFAULT 4," + SubscriptionManager.CB_ALERT_REMINDER_INTERVAL + " INTEGER DEFAULT 0," + SubscriptionManager.CB_ALERT_VIBRATE + " INTEGER DEFAULT 1," + SubscriptionManager.CB_ALERT_SPEECH + " INTEGER DEFAULT 1," + SubscriptionManager.CB_ETWS_TEST_ALERT + " INTEGER DEFAULT 0," + SubscriptionManager.CB_CHANNEL_50_ALERT + " INTEGER DEFAULT 1," + SubscriptionManager.CB_CMAS_TEST_ALERT + " INTEGER DEFAULT 0," + SubscriptionManager.CB_OPT_OUT_DIALOG + " INTEGER DEFAULT 1" + ");"); if (DBG) log("dbh.createSimInfoTable:-"); } 那么又要问了，数据库的数据从哪来？自然从SIM中读取的了。怎么读？通过AT指令读！
怎么通过AT指令读？说过了。
