APP注册SensorEventListener-Android12

android12-release

1. APP获取SensorService和传感器Sensor

可查看APP获取Sensor对象-Android12

2. 注册SensorEventListener监听

this 继承 SensorEventListener

mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);

listener == null || sensor == null 判断传入参数是否为null
mSensorListeners.size() >= MAX_LISTENER_COUNT注册监听限制MAX_LISTENER_COUNT = 128
mSensorListeners记录SensorEventListener与SensorEventQueue一一对应mSensorListeners.put(listener, queue)
new SensorEventQueue初始化连接Native层SensorEventQueue、SensorEventConnection
queue.addSensor(sensor, delayUs, maxBatchReportLatencyUs)并激活enableSensor()

frameworks/base/core/java/android/hardware/SystemSensorManager.java

    protected boolean registerListenerImpl(SensorEventListener listener, Sensor sensor,int delayUs, Handler handler, int maxBatchReportLatencyUs, int reservedFlags) {if (listener == null || sensor == null) {Log.e(TAG, "sensor or listener is null");return false;}// Trigger Sensors should use the requestTriggerSensor call.if (sensor.getReportingMode() == Sensor.REPORTING_MODE_ONE_SHOT) {Log.e(TAG, "Trigger Sensors should use the requestTriggerSensor.");return false;}if (maxBatchReportLatencyUs < 0 || delayUs < 0) {Log.e(TAG, "maxBatchReportLatencyUs and delayUs should be non-negative");return false;}if (mSensorListeners.size() >= MAX_LISTENER_COUNT) {throw new IllegalStateException("register failed, "+ "the sensor listeners size has exceeded the maximum limit "+ MAX_LISTENER_COUNT);}// Invariants to preserve:// - one Looper per SensorEventListener// - one Looper per SensorEventQueue// We map SensorEventListener to a SensorEventQueue, which holds the loopersynchronized (mSensorListeners) {SensorEventQueue queue = mSensorListeners.get(listener);if (queue == null) {Looper looper = (handler != null) ? handler.getLooper() : mMainLooper;final String fullClassName =listener.getClass().getEnclosingClass() != null? listener.getClass().getEnclosingClass().getName(): listener.getClass().getName();queue = new SensorEventQueue(listener, looper, this, fullClassName);if (!queue.addSensor(sensor, delayUs, maxBatchReportLatencyUs)) {queue.dispose();return false;}mSensorListeners.put(listener, queue);return true;} else {return queue.addSensor(sensor, delayUs, maxBatchReportLatencyUs);}}}

2.1 JNI调用及初始化SensorEventQueue、SensorEventConnection

queue(mgr->createEventQueue(clientName, mode, attributionTagName))先binder调用mSensorServer->createSensorEventConnection()创建SensorEventConnection，在new SensorEventQueue(connection)
new Receiver()实例化后onFirstRef()中mMessageQueue->getLooper()->addFd(mSensorQueue->getFd(), ... )为Handler\Looper 添加mReceiveFd = sockets[0](SensorEventConnection基于BitTube.cpp实现socket)监听，LooperCallback 回调 handleEvent() 方法

frameworks/base/core/jni/android_hardware_SensorManager.cpp

static jlong nativeInitSensorEventQueue(JNIEnv *env, jclass clazz, jlong sensorManager,jobject eventQWeak, jobject msgQ, jstring packageName,jint mode, jstring opPackageName, jstring attributionTag) {// ... ...sp<SensorEventQueue> queue(mgr->createEventQueue(clientName, mode, attributionTagName));// ... ...sp<MessageQueue> messageQueue = android_os_MessageQueue_getMessageQueue(env, msgQ);// ... ...sp<Receiver> receiver = new Receiver(queue, messageQueue, eventQWeak);receiver->incStrong((void*)nativeInitSensorEventQueue);return jlong(receiver.get());
}class Receiver : public LooperCallback {// ... ...
public:Receiver(const sp<SensorEventQueue>& sensorQueue,const sp<MessageQueue>& messageQueue,jobject receiverWeak) {JNIEnv* env = AndroidRuntime::getJNIEnv();mSensorQueue = sensorQueue;mMessageQueue = messageQueue;mReceiverWeakGlobal = env->NewGlobalRef(receiverWeak);mIntScratch = (jintArray) env->NewGlobalRef(env->NewIntArray(16));mFloatScratch = (jfloatArray) env->NewGlobalRef(env->NewFloatArray(16));}// ... ...
private:virtual void onFirstRef() {LooperCallback::onFirstRef();mMessageQueue->getLooper()->addFd(mSensorQueue->getFd(), 0,ALOOPER_EVENT_INPUT, this, mSensorQueue.get());}virtual int handleEvent(int fd, int events, void* data) {// ... ...}
};

frameworks/native/libs/sensor/SensorManager.cpp
frameworks/native/services/sensorservice/SensorService.cpp
frameworks/native/services/sensorservice/SensorEventConnection.cpp
frameworks/native/libs/sensor/BitTube.cpp
frameworks/native/libs/sensor/SensorEventQueue.cpp

void BitTube::init(size_t rcvbuf, size_t sndbuf) {int sockets[2];if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sockets) == 0) {size_t size = DEFAULT_SOCKET_BUFFER_SIZE;setsockopt(sockets[0], SOL_SOCKET, SO_RCVBUF, &rcvbuf, sizeof(rcvbuf));setsockopt(sockets[1], SOL_SOCKET, SO_SNDBUF, &sndbuf, sizeof(sndbuf));// sine we don't use the "return channel", we keep it small...setsockopt(sockets[0], SOL_SOCKET, SO_SNDBUF, &size, sizeof(size));setsockopt(sockets[1], SOL_SOCKET, SO_RCVBUF, &size, sizeof(size));fcntl(sockets[0], F_SETFL, O_NONBLOCK);fcntl(sockets[1], F_SETFL, O_NONBLOCK);mReceiveFd = sockets[0];mSendFd = sockets[1];} else {mReceiveFd = -errno;ALOGE("BitTube: pipe creation failed (%s)", strerror(-mReceiveFd));}
}

2.2 `mSendFd` 在SensorService.cpp中初始化SensorEventConnectio时添加监听

looper->addFd(mChannel->getSendFd(), ...)

frameworks/native/services/sensorservice/SensorService.cpp

sp<ISensorEventConnection> SensorService::createSensorEventConnection(const String8& packageName,int requestedMode, const String16& opPackageName, const String16& attributionTag) {// ... ...sp<SensorEventConnection> result(new SensorEventConnection(this, uid, connPackageName,requestedMode == DATA_INJECTION, connOpPackageName, attributionTag));if (requestedMode == DATA_INJECTION) {mConnectionHolder.addEventConnectionIfNotPresent(result);// Add the associated file descriptor to the Looper for polling whenever there is data to// be injected.result->updateLooperRegistration(mLooper);}return result;
}

frameworks/native/services/sensorservice/SensorEventConnection.cpp

void SensorService::SensorEventConnection::updateLooperRegistration(const sp<Looper>& looper) {Mutex::Autolock _l(mConnectionLock);updateLooperRegistrationLocked(looper);
}void SensorService::SensorEventConnection::updateLooperRegistrationLocked(const sp<Looper>& looper) {// ... ...// Add the file descriptor to the Looper for receiving acknowledegments if the app has// registered for wake-up sensors OR for sending events in the cache.int ret = looper->addFd(mChannel->getSendFd(), 0, looper_flags, this, nullptr);// ... ...
}

2.3 `enableSensor()`激活Sensor最终调用SensorService::enable

connection->sendEvents(&event, 1, nullptr) 此传感器已激活，如果请求的传感器不是“连续”传感器，则立即向下发送该传感器的最后一个已知值。
sensor->batch()、sensor->flush()、sensor->activate() 对应Sensor器件激活
connection->updateLooperRegistration(mLooper) 更新监听mSendFd

frameworks/native/services/sensorservice/SensorService.cpp

status_t SensorService::enable(const sp<SensorEventConnection>& connection,int handle, nsecs_t samplingPeriodNs, nsecs_t maxBatchReportLatencyNs, int reservedFlags,const String16& opPackageName) {// ... ...sp<SensorInterface> sensor = getSensorInterfaceFromHandle(handle);// ... ...SensorRecord* rec = mActiveSensors.valueFor(handle);if (rec == nullptr) {rec = new SensorRecord(connection);mActiveSensors.add(handle, rec);// ... ...} else {if (rec->addConnection(connection)) {// this sensor is already activated, but we are adding a connection that uses it.// Immediately send down the last known value of the requested sensor if it's not a// "continuous" sensor.if (sensor->getSensor().getReportingMode() == AREPORTING_MODE_ON_CHANGE) {// NOTE: The wake_up flag of this event may get set to// WAKE_UP_SENSOR_EVENT_NEEDS_ACK if this is a wake_up event.auto logger = mRecentEvent.find(handle);if (logger != mRecentEvent.end()) {sensors_event_t event;// Verify that the last sensor event was generated from the current activation// of the sensor. If not, it is possible for an on-change sensor to receive a// sensor event that is stale if two clients re-activate the sensor// simultaneously.if(logger->second->populateLastEventIfCurrent(&event)) {event.sensor = handle;if (event.version == sizeof(sensors_event_t)) {if (isWakeUpSensorEvent(event) && !mWakeLockAcquired) {setWakeLockAcquiredLocked(true);}connection->sendEvents(&event, 1, nullptr);if (!connection->needsWakeLock() && mWakeLockAcquired) {checkWakeLockStateLocked(&connLock);}}}}}}}// ... ...status_t err = sensor->batch(connection.get(), handle, 0, samplingPeriodNs,maxBatchReportLatencyNs);// ... ...if (err == NO_ERROR &&sensor->getSensor().getReportingMode() == AREPORTING_MODE_CONTINUOUS &&rec->getNumConnections() > 1) {connection->setFirstFlushPending(handle, true);status_t err_flush = sensor->flush(connection.get(), handle);// Flush may return error if the underlying h/w sensor uses an older HAL.if (err_flush == NO_ERROR) {rec->addPendingFlushConnection(connection.get());} else {connection->setFirstFlushPending(handle, false);}}if (err == NO_ERROR) {ALOGD_IF(DEBUG_CONNECTIONS, "Calling activate on %d", handle);err = sensor->activate(connection.get(), true);}if (err == NO_ERROR) {connection->updateLooperRegistration(mLooper);// ... ...}if (err != NO_ERROR) {// batch/activate has failed, reset our state.cleanupWithoutDisableLocked(connection, handle);}return err;
}

3. Receiver监听socket传递Sensor数据

监听socket回调handleEvent
env->CallVoidMethod() JNI调用SystemSensorManager.java中SensorEventQueue对象的dispatchSensorEvent方法

class Receiver : public LooperCallback {// ... ...
private:virtual void onFirstRef() {LooperCallback::onFirstRef();mMessageQueue->getLooper()->addFd(mSensorQueue->getFd(), 0,ALOOPER_EVENT_INPUT, this, mSensorQueue.get());}virtual int handleEvent(int fd, int events, void* data) {// ... ...if (receiverObj.get()) {env->CallVoidMethod(receiverObj.get(),gBaseEventQueueClassInfo.dispatchSensorEvent,buffer[i].sensor,mFloatScratch,status,buffer[i].timestamp);}// ... ...}
};

查看SensorService数据传递给APP-Android12

时序图