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:
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:
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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