DcTracker是在每个Phone构造的时候创建的，DcTrackerBase是DcTracker，他们的核心都是Handler。
@GSMPhone.java
public GSMPhone (Context context, CommandsInterface ci, PhoneNotifier notifier, boolean unitTestMode) {
//创建DcTracker对象，传递的参数就是当前的GSMPhone对象
mDcTracker = new DcTracker(this);
}
DcTracker作为数据链接中最重要的一个管理者核心，数据链接都会从DcTracker中发起，其中会做一些列的状态检查与判断，DcTracker处于的环节如下图中的浅蓝色部分
这里写图片描述
首先看DcTracker的构造
public DcTracker(PhoneBase p) {
super(p);
mDataConnectionTracker = this;
update();
mApnObserver = new ApnChangeObserver();
p.getContext().getContentResolver().registerContentObserver(
Telephony.Carriers.CONTENT_URI, true, mApnObserver);
initApnContexts();
for (ApnContext apnContext : mApnContexts.values()) {
// Register the reconnect and restart actions.
IntentFilter filter = new IntentFilter();
filter.addAction(INTENT_RECONNECT_ALARM + '.' + apnContext.getApnType());
filter.addAction(INTENT_RESTART_TRYSETUP_ALARM + '.' + apnContext.getApnType());
mPhone.getContext().registerReceiver(mIntentReceiver, filter, null, mPhone);
}
// Add Emergency APN to APN setting list by default to support EPDN in sim absent cases
initEmergencyApnSetting();
addEmergencyApnSetting();
mProvisionActionName = "com.android.internal.telephony.PROVISION" + p.getPhoneId();
}
首先调用的是update()，这里注册了大量的监听事件，并注册了APN参数的监听器
public void update() {
if (isActiveDataSubscription()) {
//注册各种监听器
registerForAllEvents();
//注册SIM卡状态监听器
onUpdateIcc();
//mUserDataEnabled就是用户是否打开网络开关的标志位，当为0时，表示当前数据流量被关闭
mUserDataEnabled = Settings.Global.getInt(mPhone.getContext().getContentResolver(), Settings.Global.MOBILE_DATA, 1) == 1;
}
}
接下来继续来看registerForAllEvents()和onUpdateIcc()中注册的事件类型
protected void registerForAllEvents() {
//监听射频是否打开，没有处理动作
mPhone.mCi.registerForAvailable(this, DctConstants.EVENT_RADIO_AVAILABLE, null);
//监听射频是否可用，没有处理动作
mPhone.mCi.registerForOffOrNotAvailable(this, DctConstants.EVENT_RADIO_OFF_OR_NOT_AVAILABLE, null);
//监听当前连接状态，没有处理动作
mPhone.mCi.registerForDataNetworkStateChanged(this, DctConstants.EVENT_DATA_STATE_CHANGED, null);
//监听当前通话状态，没有处理动作
mPhone.getCallTracker().registerForVoiceCallEnded (this, DctConstants.EVENT_VOICE_CALL_ENDED, null);
//监听当前通话状态，没有处理动作
mPhone.getCallTracker().registerForVoiceCallStarted (this, DctConstants.EVENT_VOICE_CALL_STARTED, null);
//监听是否PS域Attach状态
mPhone.getServiceStateTracker().registerForDataConnectionAttached(this, DctConstants.EVENT_DATA_CONNECTION_ATTACHED, null);
//监听是否PS域Detach状态
mPhone.getServiceStateTracker().registerForDataConnectionDetached(this, DctConstants.EVENT_DATA_CONNECTION_DETACHED, null);
//监听漫游状态，没有处理动作
mPhone.getServiceStateTracker().registerForRoamingOn(this, DctConstants.EVENT_ROAMING_ON, null);
//监听漫游状态，没有处理动作
mPhone.getServiceStateTracker().registerForRoamingOff(this, DctConstants.EVENT_ROAMING_OFF, null);
mPhone.getServiceStateTracker().registerForPsRestrictedEnabled(this, DctConstants.EVENT_PS_RESTRICT_ENABLED, null);
mPhone.getServiceStateTracker().registerForPsRestrictedDisabled(this, DctConstants.EVENT_PS_RESTRICT_DISABLED, null);
//监听接入技术状态
mPhone.getServiceStateTracker().registerForDataRegStateOrRatChanged(this, DctConstants.EVENT_DATA_RAT_CHANGED, null);
}
registerForAllEvents()注册了大量的事件，但是其中最重要的事件是EVENT_DATA_CONNECTION_ATTACHED
----监听PS的Attach事件（代码中看出来应该是DataRegState的状态由STATE_OUT_OF_SERVICE -> STATE_IN_SERVICE），触发时将进入onDataConnectionAttached()
protected void onUpdateIcc() {
if (mUiccController == null ) {
return;
}
IccRecords newIccRecords = getUiccRecords(UiccController.APP_FAM_3GPP);
IccRecords r = mIccRecords.get();
if (r != newIccRecords) {
if (r != null) {
r.unregisterForRecordsLoaded(this);
mIccRecords.set(null);
}
if (newIccRecords != null) {
mIccRecords.set(newIccRecords);
//监听SIM各项数据是否载入完毕
newIccRecords.registerForRecordsLoaded( this, DctConstants.EVENT_RECORDS_LOADED, null);
}
}
}
其中注册了EVENT_RECORDS_LOADED事件，这个事件在SIM卡被装载完成后被通知
紧接着在DcTracker的构造中注册了APN参数变化的监听器，在用户手动切换选择APN时这个监听器会相应，将当前的APN参数更新为用户选择的APN参数
mApnObserver = new ApnChangeObserver();
p.getContext().getContentResolver().registerContentObserver(
Telephony.Carriers.CONTENT_URI, true, mApnObserver);
接下来在initApnContexts()中会初始化好当前系统支持的ApnContexts类型，并增加紧急APN，至此DcTracker的构造就完成了，在DcTrackerBase中还会创建一些与DataConnection有关的对象，接下来看DcTrackerBase的构造内容
protected DcTrackerBase(PhoneBase phone) {
super();
mPhone = phone;
mResolver = mPhone.getContext().getContentResolver();
mUiccController = UiccController.getInstance();
mUiccController.registerForIccChanged(this, DctConstants.EVENT_ICC_CHANGED, null);
mAlarmManager =
(AlarmManager) mPhone.getContext().getSystemService(Context.ALARM_SERVICE);
mCm = (ConnectivityManager) mPhone.getContext().getSystemService(
Context.CONNECTIVITY_SERVICE); //拿到ConnectivityManager
mUserDataEnabled = getDataEnabled();
mPhone.getContext().registerReceiver(mIntentReceiver, filter, null, mPhone);
HandlerThread dcHandlerThread = new HandlerThread("DcHandlerThread");
dcHandlerThread.start();
Handler dcHandler = new Handler(dcHandlerThread.getLooper());
mDcc = DcController.makeDcc(mPhone, this, dcHandler);
mDcTesterFailBringUpAll = new DcTesterFailBringUpAll(mPhone, dcHandler);
}
其中mResolver = mPhone.getContext().getContentResolver();是拿到ContentResolver，查询数据库就是通过这个对象去操作的，比如后面的mUserDataEnabled = getDataEnabled();
mUserDataEnabled是保存在settings.db数据库中表global中的mobile_data字段
public boolean getDataEnabled() {
boolean retVal = "true".equalsIgnoreCase(SystemProperties.get(
"ro.com.android.mobiledata", "true"));
try {
if (TelephonyManager.getDefault().getSimCount() == 1) { //单卡path
retVal = Settings.Global.getInt(mResolver, Settings.Global.MOBILE_DATA,
retVal ? 1 : 0) != 0;
} else {
int phoneSubId = mPhone.getSubId(); //多卡path
retVal = TelephonyManager.getIntWithSubId(mResolver, Settings.Global.MOBILE_DATA,
phoneSubId) != 0;
}
if (DBG) log("getDataEnabled: getIntWithSubId retVal=" + retVal);
}
return retVal;
}
顺便提一下这个字段（settings.db数据库中表global中的mobile_data字段）的更新在DcTrackerBase.java中的onSetUserDataEnabled(boolean enabled)
protected void onSetUserDataEnabled(boolean enabled) {
if (TelephonyManager.getDefault().getSimCount() == 1) {
Settings.Global.putInt(mResolver, Settings.Global.MOBILE_DATA, enabled ? 1 : 0);
} else {
int phoneSubId = mPhone.getSubId();
Settings.Global.putInt(mResolver, Settings.Global.MOBILE_DATA + phoneSubId,
enabled ? 1 : 0);
}
}
其中 mUiccController.registerForIccChanged(this, DctConstants.EVENT_ICC_CHANGED, null);注册EVENT_ICC_CHANGED事件，当SIM卡发生改变时触发
其中 mPhone.getContext().registerReceiver(mIntentReceiver, filter, null, mPhone); 注册一些Intent事件，比如当手机屏幕关闭时，就会关闭数据上下行的统计，等等
接下来是比较重要的一部分，在这里只是new HandlerThread，并创建了一个新的Handler放入DcController，创建了DcController对象，在后续中还会仔细分析这个Handler
HandlerThread dcHandlerThread = new HandlerThread("DcHandlerThread");
dcHandlerThread.start();
Handler dcHandler = new Handler(dcHandlerThread.getLooper());
mDcc = DcController.makeDcc(mPhone, this, dcHandler);
mDcTesterFailBringUpAll = new DcTesterFailBringUpAll(mPhone, dcHandler);
至此，DcTracker算是完成了构造过程，接下来分析数据链接的动态过程
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