@Override
public ComponentName startService(Intent service) {
  warnIfCallingFromSystemProcess();
  return startServiceCommon(service, mUser);
}

private ComponentName startServiceCommon(Intent service, UserHandle user) {
  try {
    validateServiceIntent(service);
    service.prepareToLeaveProcess();
    ComponentName cn = ActivityManagerNative.getDefault().startService(
      mMainThread.getApplicationThread(), service, service.resolveTypeIfNeeded(
            getContentResolver()), getOpPackageName(), user.getIdentifier());

  //代码省略

    return cn;
  } catch (RemoteException e) {
    throw new RuntimeException("Failure from system", e);
  }
}

@Override
public ComponentName startService(IApplicationThread caller, Intent service,
    String resolvedType, String callingPackage, int userId)
    throws TransactionTooLargeException {

   //代码省略

  synchronized(this) {
    final int callingPid = Binder.getCallingPid();
    final int callingUid = Binder.getCallingUid();
    final long origId = Binder.clearCallingIdentity();
    ComponentName res = mServices.startServiceLocked(caller, service,
        resolvedType, callingPid, callingUid, callingPackage, userId);
    Binder.restoreCallingIdentity(origId);
    return res;
  }
}

ComponentName startServiceLocked(IApplicationThread caller, Intent service, String resolvedType,
    int callingPid, int callingUid, String callingPackage, int userId)
    throws TransactionTooLargeException {

  //代码省略

  ServiceLookupResult res =
    retrieveServiceLocked(service, resolvedType, callingPackage,
        callingPid, callingUid, userId, true, callerFg);

  //代码省略


  ServiceRecord r = res.record;

  //代码省略

  return startServiceInnerLocked(smap, service, r, callerFg, addToStarting);
}

ComponentName startServiceInnerLocked(ServiceMap smap, Intent service, ServiceRecord r,
    boolean callerFg, boolean addToStarting) throws TransactionTooLargeException {
  ProcessStats.ServiceState stracker = r.getTracker();
  if (stracker != null) {
    stracker.setStarted(true, mAm.mProcessStats.getMemFactorLocked(), r.lastActivity);
  }
  r.callStart = false;
  synchronized (r.stats.getBatteryStats()) {
    r.stats.startRunningLocked();
  }
  String error = bringUpServiceLocked(r, service.getFlags(), callerFg, false);

  //代码省略

  return r.name;
}

private final String bringUpServiceLocked(ServiceRecord r, int intentFlags, boolean execInFg,
    boolean whileRestarting) throws TransactionTooLargeException {

    //代码省略

    if (app != null && app.thread != null) {
      try {
        app.addPackage(r.appInfo.packageName, r.appInfo.versionCode, mAm.mProcessStats);
        realStartServiceLocked(r, app, execInFg);
        return null;
      } 

    //代码省略

    return null;
}

private final void realStartServiceLocked(ServiceRecord r,
    ProcessRecord app, boolean execInFg) throws RemoteException {

  //代码省略

  boolean created = false;
  try {

    //代码省略
    app.forceProcessStateUpTo(ActivityManager.PROCESS_STATE_SERVICE);
    app.thread.scheduleCreateService(r, r.serviceInfo,
        mAm.compatibilityInfoForPackageLocked(r.serviceInfo.applicationInfo),
        app.repProcState);
    r.postNotification();
    created = true;
  } catch (DeadObjectException e) {
    Slog.w(TAG, "Application dead when creating service " + r);
    mAm.appDiedLocked(app);
    throw e;
  } 

  //代码省略

  sendServiceArgsLocked(r, execInFg, true);

  //代码省略

}

public final void scheduleCreateService(IBinder token,
    ServiceInfo info, CompatibilityInfo compatInfo, int processState) {
  updateProcessState(processState, false);
  CreateServiceData s = new CreateServiceData();
  s.token = token;
  s.info = info;
  s.compatInfo = compatInfo;

  sendMessage(H.CREATE_SERVICE, s);
}

public void handleMessage(Message msg) {

    //代码省略

    case CREATE_SERVICE:
      Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceCreate");
      handleCreateService((CreateServiceData)msg.obj);
      Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
      break;

    //代码省略

}

private void handleCreateService(CreateServiceData data) {
  // If we are getting ready to gc after going to the background, well
  // we are back active so skip it.
  unscheduleGcIdler();

  LoadedApk packageInfo = getPackageInfoNoCheck(
      data.info.applicationInfo, data.compatInfo);
  Service service = null;
  try {
    java.lang.ClassLoader cl = packageInfo.getClassLoader();
    service = (Service) cl.loadClass(data.info.name).newInstance();
  } catch (Exception e) {
    if (!mInstrumentation.onException(service, e)) {
      throw new RuntimeException(
        "Unable to instantiate service " + data.info.name
        + ": " + e.toString(), e);
    }
  }

  try {
    if (localLOGV) Slog.v(TAG, "Creating service " + data.info.name);

    ContextImpl context = ContextImpl.createAppContext(this, packageInfo);
    context.setOuterContext(service);

    Application app = packageInfo.makeApplication(false, mInstrumentation);
    service.attach(context, this, data.info.name, data.token, app,
        ActivityManagerNative.getDefault());
    service.onCreate();
    mServices.put(data.token, service);
    try {
      ActivityManagerNative.getDefault().serviceDoneExecuting(
          data.token, SERVICE_DONE_EXECUTING_ANON, 0, 0);
    } catch (RemoteException e) {
      // nothing to do.
    }
  } catch (Exception e) {
    if (!mInstrumentation.onException(service, e)) {
      throw new RuntimeException(
        "Unable to create service " + data.info.name
        + ": " + e.toString(), e);
    }
  }
}

java.lang.ClassLoader cl = packageInfo.getClassLoader();
service = (Service) cl.loadClass(data.info.name).newInstance();

public Application makeApplication(boolean forceDefaultAppClass,
    Instrumentation instrumentation) {
  if (mApplication != null) {
    return mApplication;
  }

  Application app = null;

  String appClass = mApplicationInfo.className;
  if (forceDefaultAppClass || (appClass == null)) {
    appClass = "android.app.Application";
  }

  try {
    java.lang.ClassLoader cl = getClassLoader();
    if (!mPackageName.equals("android")) {
      initializeJavaContextClassLoader();
    }
    ContextImpl appContext = ContextImpl.createAppContext(mActivityThread, this);
    app = mActivityThread.mInstrumentation.newApplication(
        cl, appClass, appContext);
    appContext.setOuterContext(app);
  } catch (Exception e) {
    if (!mActivityThread.mInstrumentation.onException(app, e)) {
      throw new RuntimeException(
        "Unable to instantiate application " + appClass
        + ": " + e.toString(), e);
    }
  }
  mActivityThread.mAllApplications.add(app);
  mApplication = app;

  if (instrumentation != null) {
    try {
      instrumentation.callApplicationOnCreate(app);
    } catch (Exception e) {
      if (!instrumentation.onException(app, e)) {
        throw new RuntimeException(
          "Unable to create application " + app.getClass().getName()
          + ": " + e.toString(), e);
      }
    }
  }

  // Rewrite the R 'constants' for all library apks.
  SparseArray<String> packageIdentifiers = getAssets(mActivityThread)
      .getAssignedPackageIdentifiers();
  final int N = packageIdentifiers.size();
  for (int i = 0; i < N; i++) {
    final int id = packageIdentifiers.keyAt(i);
    if (id == 0x01 || id == 0x7f) {
      continue;
    }

    rewriteRValues(getClassLoader(), packageIdentifiers.valueAt(i), id);
  }

  return app;
}

service.onCreate();
mServices.put(data.token, service);

private final void sendServiceArgsLocked(ServiceRecord r, boolean execInFg,
    boolean oomAdjusted) throws TransactionTooLargeException {
  final int N = r.pendingStarts.size();

    //代码省略

    try {

    //代码省略

      r.app.thread.scheduleServiceArgs(r, si.taskRemoved, si.id, flags, si.intent);
    } catch (TransactionTooLargeException e) {
      if (DEBUG_SERVICE) Slog.v(TAG_SERVICE, "Transaction too large: intent="
          + si.intent);
      caughtException = e;
    } catch (RemoteException e) {
      // Remote process gone... we'll let the normal cleanup take care of this.
      if (DEBUG_SERVICE) Slog.v(TAG_SERVICE, "Crashed while sending args: " + r);
      caughtException = e;
    } 

    //代码省略
}

public final void scheduleServiceArgs(IBinder token, boolean taskRemoved, int startId,
  int flags ,Intent args) {
  ServiceArgsData s = new ServiceArgsData();
  s.token = token;
  s.taskRemoved = taskRemoved;
  s.startId = startId;
  s.flags = flags;
  s.args = args;

  sendMessage(H.SERVICE_ARGS, s);
}

public void handleMessage(Message msg) {

    //代码省略

    case SERVICE_ARGS:
      Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "serviceStart");
      handleServiceArgs((ServiceArgsData)msg.obj);
      Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
      break;

    //代码省略
}

private void handleServiceArgs(ServiceArgsData data) {
  Service s = mServices.get(data.token);
  if (s != null) {
    try {
      if (data.args != null) {
        data.args.setExtrasClassLoader(s.getClassLoader());
        data.args.prepareToEnterProcess();
      }
      int res;
      if (!data.taskRemoved) {
        res = s.onStartCommand(data.args, data.flags, data.startId);
      } else {
        s.onTaskRemoved(data.args);
        res = Service.START_TASK_REMOVED_COMPLETE;
      }

      QueuedWork.waitToFinish();

      try {
        ActivityManagerNative.getDefault().serviceDoneExecuting(
            data.token, SERVICE_DONE_EXECUTING_START, data.startId, res);
      } catch (RemoteException e) {
        // nothing to do.
      }
      ensureJitEnabled();
    } catch (Exception e) {
      if (!mInstrumentation.onException(s, e)) {
        throw new RuntimeException(
            "Unable to start service " + s
            + " with " + data.args + ": " + e.toString(), e);
      }
    }
  }
}