<manifest xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:androidprv="http://schemas.android.com/apk/prv/res/android"
   package="com.android.server.telecom"
   android:versionCode="1"
   android:versionName="1.0.0"
   coreApp="true"
   android:sharedUserId="android.uid.system">

   <application android:label="@string/telecommAppLabel"
    android:icon="@mipmap/ic_launcher_phone"
    android:allowBackup="false"
    android:supportsRtl="true"
    android:process="system"
    android:usesCleartextTraffic="false"
    android:defaultToDeviceProtectedStorage="true"
    android:directBootAware="true">
   ....
   // 包含TelecomService
   <service android:name=".components.TelecomService"
     android:singleUser="true"
     android:process="system">
    <intent-filter>
     <action android:name="android.telecom.ITelecomService" />
    </intent-filter>
   </service>
  ....
  </application>
 </manifest>

 private void startOtherServices() {
  ....
  //啟動TelecomLoaderService系統(tǒng)服務，用于加載Telecom
  mSystemServiceManager.startService(TelecomLoaderService.class);
  // 啟動telephony注冊服務，用于注冊監(jiān)聽telephony狀態(tài)的接口
  telephonyRegistry = new TelephonyRegistry(context);
  ServiceManager.addService("telephony.registry", telephonyRegistry);
 }

 public class SystemServiceManager {

  @SuppressWarnings("unchecked")
  public SystemService startService(String className) {
   final Class<SystemService> serviceClass;
   try {
    serviceClass = (Class<SystemService>)Class.forName(className);
   } catch (ClassNotFoundException ex) {
    ....
   }
   return startService(serviceClass);
  }

  // 服務的class文件來創(chuàng)建新的服務對象(服務必須繼承SystemService)
  @SuppressWarnings("unchecked")
  public <T extends SystemService> T startService(Class<T> serviceClass) {
   try {
    final String name = serviceClass.getName();
    Slog.i(TAG, "Starting " + name);
    Trace.traceBegin(Trace.TRACE_TAG_SYSTEM_SERVER, "StartService " + name);

    // Create the service.
    if (!SystemService.class.isAssignableFrom(serviceClass)) {
     throw new RuntimeException("Failed to create " + name
       + ": service must extend " + SystemService.class.getName());
    }
    final T service;
    try {
     Constructor<T> constructor = serviceClass.getConstructor(Context.class);
     service = constructor.newInstance(mContext);
    } catch (InstantiationException ex) {
     throw new RuntimeException("Failed to create service " + name
       + ": service could not be instantiated", ex);
    } 
    ....
    // Register it.
    mServices.add(service);

    // Start it.
    try {
     service.onStart();
    } catch (RuntimeException ex) {
     throw new RuntimeException("Failed to start service " + name
       + ": onStart threw an exception", ex);
    }
    return service;
   } finally {
    Trace.traceEnd(Trace.TRACE_TAG_SYSTEM_SERVER);
   }
  }
 }

 public class TelecomLoaderService extends SystemService {
  ...
  public TelecomLoaderService(Context context) {
   super(context);
   mContext = context;
   registerDefaultAppProviders();
  }

  @Override
  public void onStart() {
  }

  private void registerDefaultAppProviders() {
   final PackageManagerInternal packageManagerInternal = LocalServices.getService(
     PackageManagerInternal.class);

   // Set a callback for the package manager to query the default sms app.
   packageManagerInternal.setSmsAppPackagesProvider(
     new PackageManagerInternal.PackagesProvider() {
    @Override
    public String[] getPackages(int userId) {
     synchronized (mLock) {
     ....
     ComponentName smsComponent = SmsApplication.getDefaultSmsApplication(
       mContext, true);
     if (smsComponent != null) {
      return new String[]{smsComponent.getPackageName()};
     }
     return null;
    }
   });

   // Set a callback for the package manager to query the default dialer app.
   packageManagerInternal.setDialerAppPackagesProvider(
     new PackageManagerInternal.PackagesProvider() {
    @Override
    public String[] getPackages(int userId) {
     synchronized (mLock) {
     ....
     String packageName = DefaultDialerManager.getDefaultDialerApplication(mContext);
     if (packageName != null) {
      return new String[]{packageName};
     }
     return null;
    }
   });

   // Set a callback for the package manager to query the default sim call manager.
   packageManagerInternal.setSimCallManagerPackagesProvider(
     new PackageManagerInternal.PackagesProvider() {
    @Override
    public String[] getPackages(int userId) {
     synchronized (mLock) {
     ....
     TelecomManager telecomManager =
      (TelecomManager) mContext.getSystemService(Context.TELECOM_SERVICE);
     PhoneAccountHandle phoneAccount = telecomManager.getSimCallManager(userId);
     if (phoneAccount != null) {
      return new String[]{phoneAccount.getComponentName().getPackageName()};
     }
     return null;
    }
   });
  }
 }

 public class TelecomLoaderService extends SystemService {

  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";

  // 當前系統(tǒng)啟動的階段
  @Override
  public void onBootPhase(int phase) {
   if (phase == PHASE_ACTIVITY_MANAGER_READY) {
    registerDefaultAppNotifier();
    registerCarrierConfigChangedReceiver();
    connectToTelecom();
   }
  }

  //綁定Telecom服務
  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;
    }
   }
  }
 }

 public class TelecomLoaderService extends SystemService {

  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") thats redundant here.
     try {
      service.linkToDeath(new IBinder.DeathRecipient() {
       @Override
       public void binderDied() {
        connectToTelecom();
       }
      }, 0);
      SmsApplication.getDefaultMmsApplication(mContext, false);
      //添加Telecom服務
      ServiceManager.addService(Context.TELECOM_SERVICE, service);
      ....
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
     connectToTelecom();
    }
   }
 }

 /**
  * Implementation of the ITelecom interface.
  */
 public class TelecomService extends Service implements TelecomSystem.Component {

  @Override
  public IBinder onBind(Intent intent) {
   // 初始化整個Telecom系統(tǒng)
   initializeTelecomSystem(this);
   //返回IBinder接口
   synchronized (getTelecomSystem().getLock()) {
    return getTelecomSystem().getTelecomServiceImpl().getBinder();
   }
  }

 }

 static void initializeTelecomSystem(Context context) {
   if (TelecomSystem.getInstance() == null) {

    final NotificationManager notificationManager =
      (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
    // 用于獲取聯(lián)系人
    contactInfoHelper = new ContactInfoHelper(context);
    // 新建一個單例模式的對象
    TelecomSystem.setInstance(new TelecomSystem(....));
   }
   ....
  }
 }

 public TelecomSystem(
    Context context,
    /* 用戶未接來電通知類（不包括已接或者拒絕的電話） */
    MissedCallNotifierImplFactory missedCallNotifierImplFactory,
    /* 查詢來電信息 */
    CallerInfoAsyncQueryFactory callerInfoAsyncQueryFactory,
    /* 耳機接入狀態(tài)監(jiān)聽 */
    HeadsetMediaButtonFactory headsetMediaButtonFactory,
    /* 距離傳感器管理 */
    ProximitySensorManagerFactory proximitySensorManagerFactory,
    /* 通話時電話管理 */
    InCallWakeLockControllerFactory inCallWakeLockControllerFactory,
    /* 音頻服務管理 */
    AudioServiceFactory audioServiceFactory,
    /* 藍牙設備管理 */
    BluetoothPhoneServiceImplFactory bluetoothPhoneServiceImplFactory,
    BluetoothVoIPServiceImplFactory bluetoothVoIPServiceImplFactory,
    /* 查詢所有超時信息 */
    Timeouts.Adapter timeoutsAdapter,
    /* 響鈴播放 */
    AsyncRingtonePlayer asyncRingtonePlayer,
    /* 電話號碼幫助類 */
    PhoneNumberUtilsAdapter phoneNumberUtilsAdapter,
    /* 通話時阻斷通知 */
    InterruptionFilterProxy interruptionFilterProxy) {
   mContext = context.getApplicationContext();
   // 初始化telecom相關的feature
   TelecomFeature.makeFeature(mContext);
   // 初始化telecom的數(shù)據(jù)庫
   TelecomSystemDB.initialize(mContext);
   // 創(chuàng)建一個PhoneAccount注冊管理類
   mPhoneAccountRegistrar = new PhoneAccountRegistrar(mContext);
   ....
   // 初始化通話管家，正是它負責與上層UI的交互
   mCallsManager = new CallsManager(
     mContext, mLock, mContactsAsyncHelper,
     callerInfoAsyncQueryFactory, mMissedCallNotifier,
     mPhoneAccountRegistrar, headsetMediaButtonFactory,
     proximitySensorManagerFactory, inCallWakeLockControllerFactory,
     audioServiceFactory, bluetoothManager,
     wiredHeadsetManager, systemStateProvider,
     defaultDialerAdapter, timeoutsAdapter,AsyncRingtonePlayer,
     phoneNumberUtilsAdapter, interruptionFilterProxy);

   CallsManager.initialize(mCallsManager);
   // 注冊需要接收的廣播 
   mContext.registerReceiver(mUserSwitchedReceiver, USER_SWITCHED_FILTER);
   mContext.registerReceiver(mUserStartingReceiver, USER_STARTING_FILTER);
   mContext.registerReceiver(mFeatureChangedReceiver, FEATURE_CHANGED_FILTER);
   mContext.registerReceiver(mEmergencyReceiver, EMERGENCY_STATE_CHANGED);
   .... 
   // 所有來電與去電的處理中轉站
   mCallIntentProcessor = new CallIntentProcessor(mContext, mCallsManager);
   // 創(chuàng)建一個TelecomServiceImpl用于調(diào)用TelecomService的接口
   mTelecomServiceImpl = new TelecomServiceImpl(
     mContext, mCallsManager, mPhoneAccountRegistrar,
     new CallIntentProcessor.AdapterImpl(),
     new UserCallIntentProcessorFactory() {
      @Override
      public UserCallIntentProcessor create(Context context, UserHandle userHandle) {
       return new UserCallIntentProcessor(context, userHandle);
      }
     },
     defaultDialerAdapter,
     new TelecomServiceImpl.SubscriptionManagerAdapterImpl(),
     mLock);
   // 執(zhí)行特定的初始化操作
   initialize(mContext);
  }
 }