Android 系统服务TelecomService启动过程原理分析
由于一直负责的是Android Telephony部分的开发工作,对于通信过程的上层部分Telecom服务以及UI都没有认真研究过。最近恰好碰到一个通话方面的问题,涉及到了Telecom部分,因而就花时间仔细研究了下相关的代码。这里做一个简单的总结。这篇文章,主要以下两个部分的内容:
- 什么是Telecom服务?其作用是什么?
- Telecom模块的启动与初始化过程;
接下来一篇文章,主要以实际通话过程为例,分析下telephony收到来电后如何将电话信息发送到Telecom模块以及Telecom是如何处理来电。
什么是Telecom服务
Telecom是Android的一个系统服务,其主要作用是管理Android系统当前的通话,如来电显示,接听电话,挂断电话等功能,在Telephony模块与上层UI之间起到了一个桥梁的作用。比如,Telephony有接收到新的来电时,首先会告知Telecom,然后由Telecom服务通知上层应用来电信息,并显示来电界面。
Telecom服务对外提供了一个接口类TelecomManager,通过其提供的接口,客户端可以查询通话状态,发送通话请求以及添加通话链接等。
从Telecom进程对应的AndroidManifest.xml文件来看,Telecom进程的用户ID跟系统进程用户ID相同,是系统的核心服务。那么,其中android:process="system"这个属性值表示什么意思了?查看官方文档,这个表示Telecom将启动在进程system中,这样可以跟其他进程进行资源共享了(对于Android这个全局进程,就是SystemServer所在的进程)。
android:process
By setting this attribute to a process name that's shared with another application, you can arrange for components of both applications to run in the same process — but only if the two applications also share a user ID and be signed with the same certificate.
If the name assigned to this attribute begins with a colon (‘:'), a new process, private to the application, is created when it's needed. If the process name begins with a lowercase character, a global process of that name is created. A global process can be shared with other applications, reducing resource usage.
<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>
代码路径:
/android/applications/sources/services/Telecomm/
/android/frameworks/base/telecomm/
了解了什么是Telecom服务之后,就来看一看Telecom服务是如何启动与初始化的。
Telecom进程的启动与初始化
在SystemServer进程初始化完成启动完系统的核心服务如ActivityManagerService后,就会加载系统其它服务,这其中就包含了一个与Telecom服务启动相关的系统服务专门用于加载Telecom:
private void startOtherServices() { .... //启动TelecomLoaderService系统服务,用于加载Telecom mSystemServiceManager.startService(TelecomLoaderService.class); // 启动telephony注册服务,用于注册监听telephony状态的接口 telephonyRegistry = new TelephonyRegistry(context); ServiceManager.addService("telephony.registry", telephonyRegistry); }
调用系统服务管家SystemServiceManager的接口startService创建新的服务,并注册到系统中,最后调用onStart()启动服务。
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); } // 服务的class文件来创建新的服务对象(服务必须继承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); } } }
创建TelecomLoaderService系统服务,将系统默认的SMS应用,拨号应用以及SIM通话管理应用(不知道这个什么鬼)告知PackageManagerService(PMS),以便在适当的时候可以找到应用。
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; } }); } }
到目前,好像Telecom服务并没启动,那么究竟Telecom服务在哪里启动的了?仔细看TelecomLoaderService的源代码,其中有一个onBootPhase的函数,用于SystemServer告知系统服务目前系统启动所处的阶段。这里可以看到,等(ActivityManagerService)AMS启动完成以后,就可以开始连接Telecom服务了:
- 首先,注册默认应用(SMS/Dialer etc)通知对象,以便这些应用发送变更(如下载了一个第三方的SMS应用时,可以通知系统这一变化);
- 接着,注册运营商配置变化的广播接收器,如果配置有变化时,系统会收到通知;
- 绑定TelecomService,并将其注册到系统中。
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"; // 当前系统启动的阶段 @Override public void onBootPhase(int phase) { if (phase == PHASE_ACTIVITY_MANAGER_READY) { registerDefaultAppNotifier(); registerCarrierConfigChangedReceiver(); connectToTelecom(); } } //绑定Telecom服务 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; } } } }
服务绑定:https://developer.android.com/guide/components/bound-services.html
将服务添加到ServiceManager中,如果Telecom服务连接中断时,则重新连接:
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服务 ServiceManager.addService(Context.TELECOM_SERVICE, service); .... } @Override public void onServiceDisconnected(ComponentName name) { connectToTelecom(); } } }
绑定服务时,调用TelecomService的onBind接口,对整个Telecom系统进行初始化,并返回一个IBinder接口:
/** * Implementation of the ITelecom interface. */ public class TelecomService extends Service implements TelecomSystem.Component { @Override public IBinder onBind(Intent intent) { // 初始化整个Telecom系统 initializeTelecomSystem(this); //返回IBinder接口 synchronized (getTelecomSystem().getLock()) { return getTelecomSystem().getTelecomServiceImpl().getBinder(); } } }
Telecom系统初始化,主要工作是新建一个TelecomSystem的类,在这个类中,会对整个Telecom服务的相关类都初始化:
static void initializeTelecomSystem(Context context) { if (TelecomSystem.getInstance() == null) { final NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE); // 用于获取联系人 contactInfoHelper = new ContactInfoHelper(context); // 新建一个单例模式的对象 TelecomSystem.setInstance(new TelecomSystem(....)); } .... } }
构造一个单例TelecomSystem对象:
public TelecomSystem( Context context, /* 用户未接来电通知类(不包括已接或者拒绝的电话) */ MissedCallNotifierImplFactory missedCallNotifierImplFactory, /* 查询来电信息 */ CallerInfoAsyncQueryFactory callerInfoAsyncQueryFactory, /* 耳机接入状态监听 */ HeadsetMediaButtonFactory headsetMediaButtonFactory, /* 距离传感器管理 */ ProximitySensorManagerFactory proximitySensorManagerFactory, /* 通话时电话管理 */ InCallWakeLockControllerFactory inCallWakeLockControllerFactory, /* 音频服务管理 */ AudioServiceFactory audioServiceFactory, /* 蓝牙设备管理 */ BluetoothPhoneServiceImplFactory bluetoothPhoneServiceImplFactory, BluetoothVoIPServiceImplFactory bluetoothVoIPServiceImplFactory, /* 查询所有超时信息 */ Timeouts.Adapter timeoutsAdapter, /* 响铃播放 */ AsyncRingtonePlayer asyncRingtonePlayer, /* 电话号码帮助类 */ PhoneNumberUtilsAdapter phoneNumberUtilsAdapter, /* 通话时阻断通知 */ InterruptionFilterProxy interruptionFilterProxy) { mContext = context.getApplicationContext(); // 初始化telecom相关的feature TelecomFeature.makeFeature(mContext); // 初始化telecom的数据库 TelecomSystemDB.initialize(mContext); // 创建一个PhoneAccount注册管理类 mPhoneAccountRegistrar = new PhoneAccountRegistrar(mContext); .... // 初始化通话管家,正是它负责与上层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); // 注册需要接收的广播 mContext.registerReceiver(mUserSwitchedReceiver, USER_SWITCHED_FILTER); mContext.registerReceiver(mUserStartingReceiver, USER_STARTING_FILTER); mContext.registerReceiver(mFeatureChangedReceiver, FEATURE_CHANGED_FILTER); mContext.registerReceiver(mEmergencyReceiver, EMERGENCY_STATE_CHANGED); .... // 所有来电与去电的处理中转站 mCallIntentProcessor = new CallIntentProcessor(mContext, mCallsManager); // 创建一个TelecomServiceImpl用于调用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); // 执行特定的初始化操作 initialize(mContext); } }
Android Telephony中的PhoneAccount到底起到个什么作用了?按照源码中的说明来理解,PhoneAccount表示了不同的接听或者拨打电话的方式,比如用户可以通过SIM卡来拨打电话,也可以拨打视频电话,抑或一个紧急通话,甚至可以通过telephony内部的接口来实现拨号,而Android正是通过PhoneAccount来区分这几种通话方式的。与之相对应的一个类PhoneAccountHandle则是用于表示哪一个用户正在使用通话服务。
至此整个Telecom服务就启动完成了,这样Telecom服务就可以处理来电或者去电了。在接下来的一篇文章里,将分析下来电是如何在Telecom中传递与处理,然后发送到上层UI界面的。
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