Bundler在app中是以AIDL的方式表现的。
AIDL实现类中，有2个重要的三要素，DESCRIPTOR（描述）、Stub（存根）、Proxy（代理）。
Stub是服务端，Proxy是客户端。
客户端在拿到服务端传过来的IBunder引用，会调用asInterface，这里会根据当前的描述是否相同，如果相同说明是同一个进程。
原因在于在new的时候绑定了描述。

//AIDL中
public Stub()
{
this.attachInterface(this, DESCRIPTOR);
}
//bundler中
public void attachInterface(@Nullable IInterface owner, @Nullable String descriptor) {
        mOwner = owner;
        mDescriptor = descriptor;
}

客户端通过Proxy拿到mRemote引用调用mRemote.transact(）服务端的方法。
服务端通过transact(）回调AIDL在service的实现方法。

怎么拿到引用呢？

bindService(new Intent(xx,xxx), new ServiceConnection() {
 @Override
public void onServiceConnected(ComponentName name, IBinder service) {
//这里的service就是远程的引用
  IMyAidlInterface test = IMyAidlInterface.Stub.asInterface(service);
}
@Override
  public void onServiceDisconnected(ComponentName name) {
}
}, Context.BIND_AUTO_CREATE);

主要是通过ActivityManagerService来拿到引用的。
通过2次进程间通信。第一次是调用ASM的bindService第二次是
在服务端AcitivityThread类中handlerService方法中调用ASM的publishService中回调ServiceConnection的方法拿到引用。

private void handleBindService(BindServiceData data) {
        Service s = mServices.get(data.token);
        if (DEBUG_SERVICE)
            Slog.v(TAG, "handleBindService s=" + s + " rebind=" + data.rebind);
        if (s != null) {
            try {
                data.intent.setExtrasClassLoader(s.getClassLoader());
                data.intent.prepareToEnterProcess();
                try {
                    if (!data.rebind) {
                        IBinder binder = s.onBind(data.intent);
                        ActivityManagerNative.getDefault().publishService(
                                data.token, data.intent, binder);
                    } else {
                        s.onRebind(data.intent);
                        ActivityManagerNative.getDefault().serviceDoneExecuting(
                                data.token, SERVICE_DONE_EXECUTING_ANON, 0, 0);
                    }
                    ensureJitEnabled();
                } catch (RemoteException ex) {
                }
            } catch (Exception e) {
                if (!mInstrumentation.onException(s, e)) {
                    throw new RuntimeException(
                            "Unable to bind to service " + s
                            + " with " + data.intent + ": " + e.toString(), e);
                }
            }
        }
    }

画图表示一下过程

bindService流程图

这是ASM调用ActiveServices管理类来实现服务的注册管理的。

    int bindServiceLocked(IApplicationThread caller, IBinder token,
            Intent service, String resolvedType,
            IServiceConnection connection, int flags, int userId) {
        if (DEBUG_SERVICE) Slog.v(TAG, "bindService: " + service
                + " type=" + resolvedType + " conn=" + connection.asBinder()
                + " flags=0x" + Integer.toHexString(flags));
        final ProcessRecord callerApp = mAm.getRecordForAppLocked(caller);
        if (callerApp == null) {
            throw new SecurityException(
                    "Unable to find app for caller " + caller
                    + " (pid=" + Binder.getCallingPid()
                    + ") when binding service " + service);
        }

        ActivityRecord activity = null;
        if (token != null) {
            activity = ActivityRecord.isInStackLocked(token);
            if (activity == null) {
                Slog.w(TAG, "Binding with unknown activity: " + token);
                return 0;
            }
        }

        int clientLabel = 0;
        PendingIntent clientIntent = null;

        if (callerApp.info.uid == Process.SYSTEM_UID) {
            // Hacky kind of thing -- allow system stuff to tell us
            // what they are, so we can report this elsewhere for
            // others to know why certain services are running.
            try {
                clientIntent = service.getParcelableExtra(Intent.EXTRA_CLIENT_INTENT);
            } catch (RuntimeException e) {
            }
            if (clientIntent != null) {
                clientLabel = service.getIntExtra(Intent.EXTRA_CLIENT_LABEL, 0);
                if (clientLabel != 0) {
                    // There are no useful extras in the intent, trash them.
                    // System code calling with this stuff just needs to know
                    // this will happen.
                    service = service.cloneFilter();
                }
            }
        }

        if ((flags&Context.BIND_TREAT_LIKE_ACTIVITY) != 0) {
            mAm.enforceCallingPermission(android.Manifest.permission.MANAGE_ACTIVITY_STACKS,
                    "BIND_TREAT_LIKE_ACTIVITY");
        }

        final boolean callerFg = callerApp.setSchedGroup != Process.THREAD_GROUP_BG_NONINTERACTIVE;

        ServiceLookupResult res =
            retrieveServiceLocked(service, resolvedType,
                    Binder.getCallingPid(), Binder.getCallingUid(), userId, true, callerFg);
        if (res == null) {
            return 0;
        }
        if (res.record == null) {
            return -1;
        }
        ServiceRecord s = res.record;

        final long origId = Binder.clearCallingIdentity();

        try {
            if (unscheduleServiceRestartLocked(s, callerApp.info.uid, false)) {
                if (DEBUG_SERVICE) Slog.v(TAG, "BIND SERVICE WHILE RESTART PENDING: "
                        + s);
            }

            if ((flags&Context.BIND_AUTO_CREATE) != 0) {
                s.lastActivity = SystemClock.uptimeMillis();
                if (!s.hasAutoCreateConnections()) {
                    // This is the first binding, let the tracker know.
                    ProcessStats.ServiceState stracker = s.getTracker();
                    if (stracker != null) {
                        stracker.setBound(true, mAm.mProcessStats.getMemFactorLocked(),
                                s.lastActivity);
                    }
                }
            }

            mAm.startAssociationLocked(callerApp.uid, callerApp.processName,
                    s.appInfo.uid, s.name, s.processName);

            AppBindRecord b = s.retrieveAppBindingLocked(service, callerApp);
            ConnectionRecord c = new ConnectionRecord(b, activity,
                    connection, flags, clientLabel, clientIntent);

            IBinder binder = connection.asBinder();
            ArrayList<ConnectionRecord> clist = s.connections.get(binder);
            if (clist == null) {
                clist = new ArrayList<ConnectionRecord>();
                s.connections.put(binder, clist);
            }
            clist.add(c);
            b.connections.add(c);
            if (activity != null) {
                if (activity.connections == null) {
                    activity.connections = new HashSet<ConnectionRecord>();
                }
                activity.connections.add(c);
            }
            b.client.connections.add(c);
            if ((c.flags&Context.BIND_ABOVE_CLIENT) != 0) {
                b.client.hasAboveClient = true;
            }
            if (s.app != null) {
                updateServiceClientActivitiesLocked(s.app, c, true);
            }
            clist = mServiceConnections.get(binder);
            if (clist == null) {
                clist = new ArrayList<ConnectionRecord>();
                mServiceConnections.put(binder, clist);
            }
            clist.add(c);

            if ((flags&Context.BIND_AUTO_CREATE) != 0) {
                s.lastActivity = SystemClock.uptimeMillis();
                if (bringUpServiceLocked(s, service.getFlags(), callerFg, false) != null) {
                    return 0;
                }
            }

            if (s.app != null) {
                if ((flags&Context.BIND_TREAT_LIKE_ACTIVITY) != 0) {
                    s.app.treatLikeActivity = true;
                }
                // This could have made the service more important.
                mAm.updateLruProcessLocked(s.app, s.app.hasClientActivities
                        || s.app.treatLikeActivity, b.client);
                mAm.updateOomAdjLocked(s.app);
            }

            if (DEBUG_SERVICE) Slog.v(TAG, "Bind " + s + " with " + b
                    + ": received=" + b.intent.received
                    + " apps=" + b.intent.apps.size()
                    + " doRebind=" + b.intent.doRebind);

            if (s.app != null && b.intent.received) {
                // Service is already running, so we can immediately
                // publish the connection.
                try {
                    c.conn.connected(s.name, b.intent.binder);
                } catch (Exception e) {
                    Slog.w(TAG, "Failure sending service " + s.shortName
                            + " to connection " + c.conn.asBinder()
                            + " (in " + c.binding.client.processName + ")", e);
                }

                // If this is the first app connected back to this binding,
                // and the service had previously asked to be told when
                // rebound, then do so.
                if (b.intent.apps.size() == 1 && b.intent.doRebind) {
                    requestServiceBindingLocked(s, b.intent, callerFg, true);
                }
            } else if (!b.intent.requested) {
                requestServiceBindingLocked(s, b.intent, callerFg, false);
            }

            getServiceMap(s.userId).ensureNotStartingBackground(s);

        } finally {
            Binder.restoreCallingIdentity(origId);
        }

        return 1;
    }

• 最后ActivityManagerNative getDefault留个下次分解

 static public IActivityManager getDefault() {
        return gDefault.get();
    }

private static final Singleton<IActivityManager> gDefault = new Singleton<IActivityManager>() {
        protected IActivityManager create() {
            IBinder b = ServiceManager.getService("activity");
            if (false) {
                Log.v("ActivityManager", "default service binder = " + b);
            }
            IActivityManager am = asInterface(b);
            if (false) {
                Log.v("ActivityManager", "default service = " + am);
            }
            return am;
        }
    };