相關代碼

frameworks/base/telephony --- telephony framework
frameworks/base/telecomm --- telecomm framework 沒有詳細看
package/services/telephony --- teleService.apk
package/services/Telecomm --- telepcomm.apk 沒有詳細看
frameworks/opt/telephony --- telephony-common

Telephony流程.png

TELEPHONY_SERVICE

系統(tǒng)啟動后券敌，由systemserver.java的main方法開始：

systemserver.java
main() -> run() -> startBootstrapServices(其中啟動AMS)
->startotherServices -> AMS. systemReady 中調(diào)用startPersistentApps去啟動phone應用：

phoneapp-> 
phoneglobals->onCreat() -> 
PhoneInterfaceManager.init(this) -> public() ->
TelephonyFrameworkInitializer
                .getTelephonyServiceManager()
                .getTelephonyServiceRegisterer()
                .register(this);
//看下具體的實現(xiàn)
public ServiceRegisterer getTelephonyServiceRegisterer() {
        return new ServiceRegisterer(Context.TELEPHONY_SERVICE);
 }

如上巫员，在啟動phone過程中通過register操作座掘，將PhoneInterfaceManager注冊成為真正的Context.TELEPHONY_SERVICE的service端芦圾。
一個細節(jié)問題鸠珠，上述的getTelephonyServiceManager是在什么時候賦值的？通過搜索setTelephonyServiceManager方法边篮，發(fā)現(xiàn)是在ActivityThread中的main方法中：

調(diào)用initializeMainlineModules() ->
TelephonyFrameworkInitializer.setTelephonyServiceManager(new TelephonyServiceManager());

TelephonyServiceManager是用于管理和telephony相關的各種service鸽凶，主要是確保telephony相關的各種service能夠注冊成功。

SystemServiceRegistry

SystemServiceRegistry用于在APP端緩存各種系統(tǒng)服務齿椅，方便調(diào)用系統(tǒng)服務琉挖。其static方法如下：

       static {   
            //......
           JobSchedulerFrameworkInitializer.registerServiceWrappers();
           BlobStoreManagerFrameworkInitializer.initialize();
           TelephonyFrameworkInitializer.registerServiceWrappers();
           WifiFrameworkInitializer.registerServiceWrappers();
           StatsFrameworkInitializer.registerServiceWrappers();
           //......
       } 


   // TelephonyFrameworkInitializer 的 registerServiceWrappers方法具體實現(xiàn)：
   /**
    * Called by {@link SystemServiceRegistry}'s static initializer and registers all telephony
    * services to {@link Context}, so that {@link Context#getSystemService} can return them.
    *
    * @throws IllegalStateException if this is called from anywhere besides
    * {@link SystemServiceRegistry}
    */
   public static void registerServiceWrappers() {
       SystemServiceRegistry.registerContextAwareService(
               Context.TELEPHONY_SERVICE,
               TelephonyManager.class,
               context -> new TelephonyManager(context)
       );
       SystemServiceRegistry.registerContextAwareService(
               Context.TELEPHONY_SUBSCRIPTION_SERVICE,
               SubscriptionManager.class,
               context -> new SubscriptionManager(context)
       );
       SystemServiceRegistry.registerContextAwareService(
               Context.CARRIER_CONFIG_SERVICE,
               CarrierConfigManager.class,
               context -> new CarrierConfigManager(context)
       );
       SystemServiceRegistry.registerContextAwareService(
               Context.EUICC_SERVICE,
               EuiccManager.class,
               context -> new EuiccManager(context)
       );
       SystemServiceRegistry.registerContextAwareService(
               Context.EUICC_CARD_SERVICE,
               EuiccCardManager.class,
               context -> new EuiccCardManager(context)
       );
       SystemServiceRegistry.registerContextAwareService(
               Context.TELEPHONY_IMS_SERVICE,
               ImsManager.class,
               context -> new ImsManager(context)
       );
   }

那么SystemServiceRegistry的調(diào)用是在什么時候呢？

    //ConextImpl.java
    final Object[] mServiceCache = SystemServiceRegistry.createServiceCache();

當ConextImpl對象創(chuàng)建時涣脚，其屬性就會創(chuàng)建示辈，由于上述所說，SystemServiceRegistry有static代碼塊遣蚀，因此該代碼塊會在第一次使用時就會加載矾麻。即在ConextImpl對象創(chuàng)建好之前纱耻，相關的服務就已經(jīng)在其中注冊了。

Telcommservice

systemserver.java
main() -> run() -> startBootstrapServices(其中啟動AMS)
->startotherServices -> 去StartTelecomLoaderService

            t.traceBegin("StartTelecomLoaderService");
            mSystemServiceManager.startService(TelecomLoaderService.class);
            t.traceEnd();

后面當完成開機后险耀，在AMS的finishBooting中去執(zhí)行
// Let system services know.
mSystemServiceManager.startBootPhase(t, SystemService.PHASE_BOOT_COMPLETED);
這個方法中回去回調(diào)service.onBootPhase(mCurrentPhase)弄喘。
繼續(xù)查看TelecomLoaderService的onBootPhase實現(xiàn)：

    @Override
    public void onBootPhase(int phase) {
        if (phase == PHASE_ACTIVITY_MANAGER_READY) {
            registerDefaultAppNotifier();
            registerCarrierConfigChangedReceiver();
            // core services will have already been loaded.
            setupServiceRepository();
            connectToTelecom();
        }
    }
    private void connectToTelecom() {
        synchronized (mLock) {
            if (mServiceConnection != null) {
                // TODO: Is unbinding worth doing or wait for system to rebind?
                mContext.unbindService(mServiceConnection);
                mServiceConnection = null;
            }

            TelecomServiceConnection serviceConnection = new TelecomServiceConnection();
            Intent intent = new Intent(SERVICE_ACTION);
            intent.setComponent(SERVICE_COMPONENT);
            int flags = Context.BIND_IMPORTANT | Context.BIND_FOREGROUND_SERVICE
                    | Context.BIND_AUTO_CREATE;

            // Bind to Telecom and register the service
            if (mContext.bindServiceAsUser(intent, serviceConnection, flags, UserHandle.SYSTEM)) {
                mServiceConnection = serviceConnection;
            }
        }
    }
    private static final ComponentName SERVICE_COMPONENT = new ComponentName(
            "com.android.server.telecom",
            "com.android.server.telecom.components.TelecomService");

    private static final String SERVICE_ACTION = "com.android.ITelecomService";

可以看到TelecomLoaderService去bind了TelecomService，TelecomService做為TelecomLoaderService的服務端甩牺，實現(xiàn)了ITelecomLoader.Stub：

public class TelecomService extends Service implements TelecomSystem.Component {

    @Override
    public IBinder onBind(Intent intent) {
        Log.d(this, "onBind");
        //Task9999555-zhengpinhuang@tcl.com-Mobile data off-begin
        TelecomGlobals.createInstance(getApplicationContext());
        CarrierConfigManagerEx.init(getApplicationContext());
        //Task9999555-zhengpinhuang@tcl.com-Mobile data off-end
        return new ITelecomLoader.Stub() {
            @Override
            public ITelecomService createTelecomService(IInternalServiceRetriever retriever) {
                InternalServiceRetrieverAdapter adapter =
                        new InternalServiceRetrieverAdapter(retriever);
                initializeTelecomSystem(TelecomService.this, adapter);
                synchronized (getTelecomSystem().getLock()) {
                    return getTelecomSystem().getTelecomServiceImpl().getBinder();
                }
            }
        };
    }
}

接下去看下蘑志，TelecomLoaderService在ServiceConnected成功后做了什么？

    private class TelecomServiceConnection implements ServiceConnection {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            // Normally, we would listen for death here, but since telecom runs in the same process
            // as this loader (process="system") that's redundant here.
            try {
                ITelecomLoader telecomLoader = ITelecomLoader.Stub.asInterface(service);
                ITelecomService telecomService = telecomLoader.createTelecomService(mServiceRepo);

                SmsApplication.getDefaultMmsApplication(mContext, false);
                ServiceManager.addService(Context.TELECOM_SERVICE, telecomService.asBinder());

                //......省略部分實現(xiàn)
               
            } catch (RemoteException e) {
                Slog.w(TAG, "Failed linking to death.");
            }
        }

可以看到在拿到service后贬派，第一時間就是調(diào)用createTelecomService急但，真正的實現(xiàn)是在TelecomLoaderService的service端，就是上面提到的實現(xiàn)了ITelecomLoader.Stub的地方搞乏。

        return new ITelecomLoader.Stub() {
            @Override
            public ITelecomService createTelecomService(IInternalServiceRetriever retriever) {
                InternalServiceRetrieverAdapter adapter =
                        new InternalServiceRetrieverAdapter(retriever);
                initializeTelecomSystem(TelecomService.this, adapter);
                synchronized (getTelecomSystem().getLock()) {
                    return getTelecomSystem().getTelecomServiceImpl().getBinder();
                }
            }
        };

getTelecomServiceImpl的實現(xiàn)可以看到：

    public TelecomServiceImpl getTelecomServiceImpl() {
        return mTelecomServiceImpl;
    }

mTelecomServiceImpl是在TelecomSystem的構造方法里面new的波桩。再看下getBinder的實現(xiàn)：

    public ITelecomService.Stub getBinder() {
        return mBinderImpl;
    }
    private final ITelecomService.Stub mBinderImpl = new ITelecomService.Stub() {
        @Override
        public PhoneAccountHandle getDefaultOutgoingPhoneAccount(String uriScheme,
                String callingPackage, String callingFeatureId) {
}

可以看到這里是真正telecomservice的實現(xiàn)端，是一個匿名內(nèi)部類查描。再一步步往回走突委，在拿到真正的telecomservice后，通過ServiceManager.addService將其加入到ServiceManager中冬三。

方法總結

上面總結了很多系統(tǒng)service的啟動和注冊流程匀油，那么對于這些系統(tǒng)的service，如何在看源碼的時候快速定位到具體service的實現(xiàn)呢勾笆？在已經(jīng)知道答案的情況下敌蚜，我個人大致反推了一下，方便后續(xù)查看其它系統(tǒng)service時能夠快速定位窝爪。
1弛车、假設現(xiàn)在要Context.TELECOM_SERVICE的具體實現(xiàn)，從代碼可以知道這個service對應的標識是：

    public static final String TELECOM_SERVICE = "telecom";

2蒲每、adb shell service list|grep -rin telecom 結果如下：

telecom: [com.android.internal.telecom.ITelecomService]
看到對應的aidl接口是ITelecomService.aidl

3纷跛、代碼全局搜索"extends ITelecomService.stub" ，如果沒有再搜索 "new ITelecomService.stub" 邀杏，因為有部分service端是匿名的類贫奠，telcom service就是這樣的。

完成上面3步望蜡，這些系統(tǒng)service的真正實現(xiàn)的地方基本就定位到了唤崭。

參考內(nèi)容

如何實現(xiàn)服務器端調(diào)用應用端的例子。
https://cloud.tencent.com/developer/article/1600478
解析telephonymanager和telecom的文章脖律，里面的很多時序圖很好驱犹。
https://blog.csdn.net/jason_wzn/article/details/58164251
https://blog.csdn.net/ZhongGuoRenMei/article/details/97037870