Android——4.2

            APN，这东西对于刚接触的人来说并非那么好理解。对于3G移植上网不可缺少，这里记录一下。

                                              撰写不易,转载请注明出处：http://blog.csdn.net/jscese/article/details/41248939

概念：

 APN(Access Point Name),也就是 接入点 ，移动设备使用数据流量上网必须配置的一个參数，代表以何种方式来连接服务台开启数据流量功能.

一般有訪问WAP或者connect 因特网，国内的运营商2G，3G标识例如以下：

移动公司：2G:GSM、3G:TD-SCDMA
联通公司：2G:GSM、3G:WCDMA
电信公司：2G:CDMA、3G:CDMA2000

关于详细某个运营商的几G网络 的APN 是什么详细可參考/device/sample/etc/apns-full-conf.xml

这个xml文件里有google预置的多国经常使用的APN

使用：

 apns-full-conf.xml

上面说道了apns-full-conf.xml 这个配置文件，这里面基本上是这种模块：

  <apn carrier="沃3G连接互联网 (China Unicom)"
      mcc="460"
      mnc="01"
      apn="3gnet"
      type="default,supl"
  />

其他选项都是网络參数，当中的apn就是我们最重要的接入点.也可自行加入apn属性模块.

移植3G时，就须要用到这个xml配置文件了。在android的device.mk 里面加个PRODUCT_COPY_FILES：

PRODUCT_COPY_FILES += 

     device/sample/etc/apns-full-conf.xml:system/etc/apns-conf.xml

telephony.db

这个文件被载入的地方可參考/packages/providers/TelephonyProvider/src/com/android/providers/telephony/TelephonyProvider.java：

    private static final String DATABASE_NAME = "telephony.db";  //数据库db文件

    private static final String PARTNER_APNS_PATH = "etc/apns-conf.xml";  //上面说到的copy到系统system/etc文件夹下

...

    private static class DatabaseHelper extends SQLiteOpenHelper {
        // Context to access resources with
        private Context mContext;

        /**
         * DatabaseHelper helper class for loading apns into a database.
         *
         * @param context of the user.
         */
        public DatabaseHelper(Context context) {
            super(context, DATABASE_NAME, null, getVersion(context));
            mContext = context;
        }

...
        @Override
        public void onCreate(SQLiteDatabase db) {
            // Set up the database schema
            db.execSQL("CREATE TABLE " + CARRIERS_TABLE +    //建表
                "(_id INTEGER PRIMARY KEY," +
                    "name TEXT," +
                    "numeric TEXT," +
                    "mcc TEXT," +
                    "mnc TEXT," +
                    "apn TEXT," +
                    "user TEXT," +
                    "server TEXT," +
                    "password TEXT," +
                    "proxy TEXT," +
                    "port TEXT," +
                    "mmsproxy TEXT," +
                    "mmsport TEXT," +
                    "mmsc TEXT," +
                    "authtype INTEGER," +
                    "type TEXT," +
                    "current INTEGER," +
                    "protocol TEXT," +
                    "roaming_protocol TEXT," +
                    "carrier_enabled BOOLEAN," +
                    "bearer INTEGER);");

            initDatabase(db);
        }
    private void initDatabase(SQLiteDatabase db) {

...

            // Environment.getRootDirectory() is a fancy way of saying ANDROID_ROOT or "/system".
            File confFile = new File(Environment.getRootDirectory(), PARTNER_APNS_PATH);      //这里就是载入解析 load进db 了
            FileReader confreader = null;
            try {
                confreader = new FileReader(confFile);
                confparser = Xml.newPullParser();
                confparser.setInput(confreader);
                XmlUtils.beginDocument(confparser, "apns");

                // Sanity check. Force internal version and confidential versions to agree
                int confversion = Integer.parseInt(confparser.getAttributeValue(null, "version"));
                if (publicversion != confversion) {
                    throw new IllegalStateException("Internal APNS file version doesn't match "
                            + confFile.getAbsolutePath());
                }

                loadApns(db, confparser);
            } 

...

   }

}

由于Content Provider採用的是懒载入机制，所以仅仅有检測load上sim卡的时候才会被创建这个db：

可使用sqlite3查看：

createAllApnList

 在android中数据流量由/frameworks/opt/telephony/src/java/com/android/internal/telephony/DataConnectionTracker.java

以及它的子类GsmDataConnectionTracker.java(GSM模式) 或者 CdmaDataConnectionTracker.java(CDMA模式)，(前者为移动，联通，后者为电信专用)

来控制，当中启动数据流量开关为onSetUserDataEnabled(boolean enabled).

这里单以GSM模式来说，在SIM 被load时调用：

    private void onRecordsLoaded() {
        if (DBG) log("onRecordsLoaded: createAllApnList");
        createAllApnList();
        if(!mUserDataEnabled)
            return;//jscese add judgement
        if (mPhone.mCM.getRadioState().isOn()) {
            if (DBG) log("onRecordsLoaded: notifying data availability");
            notifyOffApnsOfAvailability(Phone.REASON_SIM_LOADED);
        }
        setupDataOnReadyApns(Phone.REASON_SIM_LOADED);
    }

调用进createAllApnList

    /**
     * Based on the sim operator numeric, create a list for all possible
     * Data Connections and setup the preferredApn.
     */
    private void createAllApnList() {
        mAllApns = new ArrayList<ApnSetting>();
        IccRecords r = mIccRecords.get();
        String operator = (r != null) ? r.getOperatorNumeric() : "";
        if (operator != null) {
            String selection = "numeric = '" + operator + "'";
            // query only enabled apn.
            // carrier_enabled : 1 means enabled apn, 0 disabled apn.
            selection += " and carrier_enabled = 1";
            if (DBG) log("createAllApnList: selection=" + selection);

            Cursor cursor = mPhone.getContext().getContentResolver().query(   //用当前SIM卡相应的运营商查询系统的全部APN。往下调用createApnList
                    Telephony.Carriers.CONTENT_URI, null, selection, null, null);

            if (cursor != null) {
                if (cursor.getCount() > 0) {
                    mAllApns = createApnList(cursor);  //能够跟进去看查询Telephony.Carriers并返回一个Apn的list
                }
                cursor.close();
            }
        }

        if (mAllApns.isEmpty()) {
            if (DBG) log("createAllApnList: No APN found for carrier: " + operator);
            mPreferredApn = null;
            // TODO: What is the right behaviour?

            //notifyNoData(GsmDataConnection.FailCause.MISSING_UNKNOWN_APN);
        } else {
            mPreferredApn = getPreferredApn();
            if (mPreferredApn != null && !mPreferredApn.numeric.equals(operator)) {
                mPreferredApn = null;
                setPreferredApn(-1);
            }
            if (DBG) log("createAllApnList: mPreferredApn=" + mPreferredApn);
        }
        if (DBG) log("createAllApnList: X mAllApns=" + mAllApns);
    }

onSetUserDataEnabled(true)：

 代表打开数据流量。终于调用到  

private boolean trySetupData(ApnContext apnContext)

{

...

       if (apnContext.getState() == DctConstants.State.IDLE) {
                ArrayList<ApnSetting> waitingApns = buildWaitingApns(apnContext.getApnType());

//使用用户设置的preferred APN构建一个可用于数据连接的备选APN列表，即waitingApns列表（当有preferred APN，该列表就仅仅有一个）。


//若用户没有设置preferred APN，则将全部类型匹配的APN加入到waitingApns列表（如default类型）

                if (waitingApns.isEmpty()) {
                    if (DBG) log("trySetupData: No APN found");
                    notifyNoData(GsmDataConnection.FailCause.MISSING_UNKNOWN_APN, apnContext);
                    notifyOffApnsOfAvailability(apnContext.getReason());
                    return false;
                } else {
                    apnContext.setWaitingApns(waitingApns);
                    if (DBG) {
                        log ("trySetupData: Create from mAllApns : " + apnListToString(mAllApns));
                    }
                }
            }

            if (DBG) {
                log ("Setup watingApns : " + apnListToString(apnContext.getWaitingApns()));
            }
            // apnContext.setReason(apnContext.getReason());
            boolean retValue = setupData(apnContext);   // waitingApns列表中有可用的APN时，尝试建立连接
            notifyOffApnsOfAvailability(apnContext.getReason());
            return retValue;

...

}

另外几个对apn操作的几个函数都在这个文件中面。分别的作用例如以下：

onApnChanged：当APN被用户更改时，将调用到此函数，又一次建立数据连接

setPreferredApn：当用户没有设置preferred APN时，将当前数据连接成功的那个APN设置为preferred APN。

能够去看onDataSetupComplete时的操作。

getPreferredApn：用户获取用户设置的preferred APN，这个在上面说到的createAllApnList时会去获取一次。看是否存在.

对于这个preferredApn会以xml的形式保存在：

shell@android:/data/data/com.android.providers.telephony/shared_prefs # cat preferred-apn.xml
ml                                                                            <
<?
xml version='1.0' encoding='utf-8' standalone='yes' ?>
<map>
<long name="apn_id" value="1124" />
</map>

这是代表打开数据流量成功之后保存的apn map。能够像上面一样去 telephony.db里面查查看看：

sqlite> select * from carriers where _id='1124';
1124|沃3G连接互联网 (China Unicom)|46001|460|01|3gnet|||||||||-1|default,supl|1|IP|IP|1|0

这里仅仅是分析了一下apn的由来以及在framework层的使用，终于是通过RIL.java 的setupDataCall通过一个rild 的socket发请求到hardware的ril.cpp：

public void
    setupDataCall(String radioTechnology, String profile, String apn, /*上面传下来的apn*/
            String user, String password, String authType, String protocol,
            Message result) {
        RILRequest rr
                = RILRequest.obtain(RIL_REQUEST_SETUP_DATA_CALL, result);

        rr.mp.writeInt(7);

        rr.mp.writeString(radioTechnology);
        rr.mp.writeString(profile);
        rr.mp.writeString(apn);
        rr.mp.writeString(user);
        rr.mp.writeString(password);
        rr.mp.writeString(authType);
        rr.mp.writeString(protocol);

        if (RILJ_LOGD) riljLog(rr.serialString() + "> "
                + requestToString(rr.mRequest) + " " + radioTechnology + " "
                + profile + " " + apn + " " + user + " "
                + password + " " + authType + " " + protocol);

        send(rr); //里面就是 socket了
    }

再之后怎么获取到这个socket event处理而且交给reference-ril 发送这个apn接入网路可參考我前面的博客：

Android——RIL 机制源代码分析  

Android——4.2 - 3G移植之路之 reference-ril .pppd 拨号上网 (三)