SensorService数据传递给APK

APK调用SensorService

AS下载Source for Android 29，创建APP导入Android.jar，直接查看可调用的API
网址查看：https://developer.android.google.cn/reference/android/hardware/SensorManager

 * public class SensorActivity extends Activity implements SensorEventListener {
 *     private final SensorManager mSensorManager;
 *     private final Sensor mAccelerometer;
 *
 *     public SensorActivity() {
 *         mSensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);
 *         mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
 *     }
 *
 *     protected void onResume() {
 *         super.onResume();
 *         mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);
 *     }
 *
 *     protected void onPause() {
 *         super.onPause();
 *         mSensorManager.unregisterListener(this);
 *     }
 *
 *     public void onAccuracyChanged(Sensor sensor, int accuracy) {
 *     }
 *
 *     public void onSensorChanged(SensorEvent event) {
 *     }
 * }

1. 获取对应Sensor
2. 注册SensorEventListener监听，回调onSensorChanged方法

getSystemService(SENSOR_SERVICE)

获取的SensorManager是SystemServiceRegistry.java注册SystemSensorManager
frameworks/base/core/java/android/app/SystemServiceRegistry.java

    static {
        //......
        registerService(Context.SENSOR_SERVICE, SensorManager.class,
                new CachedServiceFetcher<SensorManager>() {
            @Override
            public SensorManager createService(ContextImpl ctx) {
                return new SystemSensorManager(ctx.getOuterContext(),
                  ctx.mMainThread.getHandler().getLooper());
            }});
        //......
    }

注册SensorEventListener

SensorEventListener是通过SystemSensorManager注册/注销
frameworks/base/core/java/android/hardware/SystemSensorManager.java

    /** @hide */
    @Override
    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 looper
        synchronized (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);
            }
        }
    }

    /** @hide */
    @Override
    protected void unregisterListenerImpl(SensorEventListener listener, Sensor sensor) {
        // Trigger Sensors should use the cancelTriggerSensor call.
        if (sensor != null && sensor.getReportingMode() == Sensor.REPORTING_MODE_ONE_SHOT) {
            return;
        }

        synchronized (mSensorListeners) {
            SensorEventQueue queue = mSensorListeners.get(listener);
            if (queue != null) {
                boolean result;
                if (sensor == null) {
                    result = queue.removeAllSensors();
                } else {
                    result = queue.removeSensor(sensor, true);
                }
                if (result && !queue.hasSensors()) {
                    mSensorListeners.remove(listener);
                    queue.dispose();
                }
            }
        }
    }

注释很清楚了

• - one Looper per SensorEventListener
• - one Looper per SensorEventQueue
• We map SensorEventListener to a SensorEventQueue, which holds the looper

SensorEventQueue 调用 dispatchSensorEvent

问题来了，这个 dispatchSensorEvent 是谁触发的？？？

1、不管其他看 dispatchSensorEvent 中调用 mListener.onSensorChanged(t); 传递给了APP监听SensorEventListener 
2、SensorEventQueue 继承 BaseEventQueue 

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

    static final class SensorEventQueue extends BaseEventQueue {
        private final SensorEventListener mListener;
        private final SparseArray<SensorEvent> mSensorsEvents = new SparseArray<SensorEvent>();

        public SensorEventQueue(SensorEventListener listener, Looper looper,
                SystemSensorManager manager, String packageName) {
            super(looper, manager, OPERATING_MODE_NORMAL, packageName);
            mListener = listener;
        }
        // ... ...
        @Override
        protected void dispatchSensorEvent(int handle, float[] values, int inAccuracy,
                long timestamp) {
            final Sensor sensor = mManager.mHandleToSensor.get(handle);
            if (sensor == null) {
                // sensor disconnected
                return;
            }

            SensorEvent t = null;
            synchronized (mSensorsEvents) {
                t = mSensorsEvents.get(handle);
            }

            if (t == null) {
                // This may happen if the client has unregistered and there are pending events in
                // the queue waiting to be delivered. Ignore.
                return;
            }
            // Copy from the values array.
            System.arraycopy(values, 0, t.values, 0, t.values.length);
            t.timestamp = timestamp;
            t.accuracy = inAccuracy;
            t.sensor = sensor;

            // call onAccuracyChanged() only if the value changes
            final int accuracy = mSensorAccuracies.get(handle);
            if ((t.accuracy >= 0) && (accuracy != t.accuracy)) {
                mSensorAccuracies.put(handle, t.accuracy);
                mListener.onAccuracyChanged(t.sensor, t.accuracy);
            }
            mListener.onSensorChanged(t);
        }
        // ... ...
    }

BaseEventQueue

1、JNI调用初始化nativeInitBaseEventQueue
2、dispatchSensorEvent子类SensorEventQueue 实现

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

    private abstract static class BaseEventQueue {
        // ... ...
        BaseEventQueue(Looper looper, SystemSensorManager manager, int mode, String packageName) {
            if (packageName == null) packageName = "";
            mNativeSensorEventQueue = nativeInitBaseEventQueue(manager.mNativeInstance,
                    new WeakReference<>(this), looper.getQueue(),
                    packageName, mode, manager.mContext.getOpPackageName());
            mCloseGuard.open("dispose");
            mManager = manager;
        }
        // ... ...
        @UnsupportedAppUsage
        protected abstract void dispatchSensorEvent(int handle, float[] values, int accuracy,
                long timestamp);
        // ... ...
    }

android_hardware_SensorManager.cpp 创建 SensorEventQueue.cpp

1、nativeInitSensorEventQueue 实际是底层 SensorEventQueue.cpp 创建
2、SensorEventQueue作为参数，创建接收器 Receiver

frameworks/base/core/jni/android_hardware_SensorManager.cpp

static const JNINativeMethod gBaseEventQueueMethods[] = {
    {"nativeInitBaseEventQueue",
             "(JLjava/lang/ref/WeakReference;Landroid/os/MessageQueue;Ljava/lang/String;ILjava/lang/String;)J",
             (void*)nativeInitSensorEventQueue },
    // ... ...
};

static jlong nativeInitSensorEventQueue(JNIEnv *env, jclass clazz, jlong sensorManager,
        jobject eventQWeak, jobject msgQ, jstring packageName, jint mode) {
    SensorManager* mgr = reinterpret_cast<SensorManager*>(sensorManager);
    ScopedUtfChars packageUtf(env, packageName);
    String8 clientName(packageUtf.c_str());
    sp<SensorEventQueue> queue(mgr->createEventQueue(clientName, mode));

    if (queue == NULL) {
        jniThrowRuntimeException(env, "Cannot construct native SensorEventQueue.");
        return 0;
    }

    sp<MessageQueue> messageQueue = android_os_MessageQueue_getMessageQueue(env, msgQ);
    if (messageQueue == NULL) {
        jniThrowRuntimeException(env, "MessageQueue is not initialized.");
        return 0;
    }

    sp<Receiver> receiver = new Receiver(queue, messageQueue, eventQWeak);
    receiver->incStrong((void*)nativeInitSensorEventQueue);
    return jlong(receiver.get());
}

SensorManager.cpp 创建 SensorEventQueue.cpp

1、创建 SensorEventConnection
2、SensorEventConnection 作为参数创建 SensorEventQueue

frameworks/native/services/sensorservice/hidl/SensorManager.cpp

sp<SensorEventQueue> SensorManager::createEventQueue(String8 packageName, int mode) {
    sp<SensorEventQueue> queue;

    Mutex::Autolock _l(mLock);
    while (assertStateLocked() == NO_ERROR) {
        sp<ISensorEventConnection> connection =
                mSensorServer->createSensorEventConnection(packageName, mode, mOpPackageName);
        if (connection == nullptr) {
            // SensorService just died or the app doesn't have required permissions.
            ALOGE("createEventQueue: connection is NULL.");
            return nullptr;
        }
        queue = new SensorEventQueue(connection);
        break;
    }
    return queue;
}

SensorEventQueue 实际是通过 SensorEventConnection 通信

SensorEventQueue.cpp 代码也可看出实际是SensorEventConnection通信

1、通过 SensorEventConnection 调用通信,实际是基于 BitTube 通信
2、write/read 通过 BitTube::sendObjects/BitTube::recvObjects

frameworks/native/libs/sensor/SensorEventQueue.cpp

// ... ...
void SensorEventQueue::onFirstRef()
{
    mSensorChannel = mSensorEventConnection->getSensorChannel();
}

int SensorEventQueue::getFd() const
{
    return mSensorChannel->getFd();
}

ssize_t SensorEventQueue::write(const sp<BitTube>& tube,
        ASensorEvent const* events, size_t numEvents) {
    return BitTube::sendObjects(tube, events, numEvents);
}
// ... ...

Receiver 通过 AndroidRuntime::getJNIEnv() 执行 dispatchSensorEvent

问题又来了，哪这个 handleEvent 又是谁触发的？？？ 目前看是BitTube socket 通信触发

1、JNI gBaseEventQueueClassInfo.dispatchSensorEventgBaseEventQueueClassInfo.dispatchSensorEvent到SensorEventQueue.dispatchSensorEvent
2、mSensorQueue->getFd() 实际获通过 SensorEventConnection 获取 BitTube的mReceiveFd = sockets[0]
3、handler/Looper 轮询回调 LooperCallback，POLL_CALLBACK某个被监听fd被触发回调response.request.callback->handleEvent(fd, events, data);

class Receiver : public LooperCallback {
    // ... ...
    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) {
        JNIEnv* env = AndroidRuntime::getJNIEnv();
        // ... ...
                // ... ...
                    if (receiverObj.get()) {
                        env->CallVoidMethod(receiverObj.get(),
                                            gBaseEventQueueClassInfo.dispatchFlushCompleteEvent,
                                            buffer[i].meta_data.sensor);
                    }
                // ... ...
                    if (receiverObj.get()) {
                        int type = buffer[i].additional_info.type;
                        int serial = buffer[i].additional_info.serial;
                        env->CallVoidMethod(receiverObj.get(),
                                            gBaseEventQueueClassInfo.dispatchAdditionalInfoEvent,
                                            buffer[i].sensor,
                                            type, serial,
                                            mFloatScratch,
                                            mIntScratch,
                                            buffer[i].timestamp);
                    }
                // ... ...
                    if (receiverObj.get()) {
                        env->CallVoidMethod(receiverObj.get(),
                                            gBaseEventQueueClassInfo.dispatchSensorEvent,
                                            buffer[i].sensor,
                                            mFloatScratch,
                                            status,
                                            buffer[i].timestamp);
                    }
                // ... ...
};

SensorEventConnection / BitTube

1、mChannel = new BitTube基于BitTube实现通信
2、SensorService::threadLoop()中connection->sendEvent触发经过SensorEventConnection::sendEvents方法
3、SensorEventQueue::write 实际触发 BitTube::sendObjects(tube, events, numEvents);

SensorService::SensorEventConnection::SensorEventConnection(
        const sp<SensorService>& service, uid_t uid, String8 packageName, bool isDataInjectionMode,
        const String16& opPackageName, bool hasSensorAccess)
    : mService(service), mUid(uid), mWakeLockRefCount(0), mHasLooperCallbacks(false),
      mDead(false), mDataInjectionMode(isDataInjectionMode), mEventCache(nullptr),
      mCacheSize(0), mMaxCacheSize(0), mTimeOfLastEventDrop(0), mEventsDropped(0),
      mPackageName(packageName), mOpPackageName(opPackageName), mDestroyed(false),
      mHasSensorAccess(hasSensorAccess) {
    mChannel = new BitTube(mService->mSocketBufferSize);
#if DEBUG_CONNECTIONS
    mEventsReceived = mEventsSentFromCache = mEventsSent = 0;
    mTotalAcksNeeded = mTotalAcksReceived = 0;
#endif
}
// ... ...
status_t SensorService::SensorEventConnection::sendEvents(
        sensors_event_t const* buffer, size_t numEvents,
        sensors_event_t* scratch,
        wp<const SensorEventConnection> const * mapFlushEventsToConnections) {
    // filter out events not for this connection
    // ... ...
    if (scratch) {
        // ... ...
    } else {
        if (hasSensorAccess()) {
            scratch = const_cast<sensors_event_t *>(buffer);
            count = numEvents;
        } else {
            sanitizedBuffer.reset(new sensors_event_t[numEvents]);
            scratch = sanitizedBuffer.get();
            for (size_t i = 0; i < numEvents; i++) {
                if (buffer[i].type == SENSOR_TYPE_META_DATA) {
                    scratch[count++] = buffer[i++];
                }
            }
        }
    }
    // ... ...
    if (mCacheSize != 0) {
        // There are some events in the cache which need to be sent first. Copy this buffer to
        // the end of cache.
        appendEventsToCacheLocked(scratch, count);
        return status_t(NO_ERROR);
    }

    int index_wake_up_event = -1;
    if (hasSensorAccess()) {
        index_wake_up_event = findWakeUpSensorEventLocked(scratch, count);
        if (index_wake_up_event >= 0) {
            scratch[index_wake_up_event].flags |= WAKE_UP_SENSOR_EVENT_NEEDS_ACK;
            ++mWakeLockRefCount;
#if DEBUG_CONNECTIONS
            ++mTotalAcksNeeded;
#endif
        }
    }

    // NOTE: ASensorEvent and sensors_event_t are the same type.
    // 3、SensorEventQueue::write 实际触发 BitTube::sendObjects(tube, events, numEvents);
    ssize_t size = SensorEventQueue::write(mChannel,
                                    reinterpret_cast<ASensorEvent const*>(scratch), count);
    // ... ...
    return size < 0 ? status_t(size) : status_t(NO_ERROR);
}
// ... ...

BitTube 通过socket 通信Fd触发 LooperCallback类

1、BitTube::sendObjects/BitTube::recvObjects 通过socket 通信Fd触发 handler/Looper LooperCallback类回调Receiver::handleEvent

namespace android {
// ... ...
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));
    }
}
// ... ...
ssize_t BitTube::write(void const* vaddr, size_t size)
{
    ssize_t err, len;
    do {
        len = ::send(mSendFd, vaddr, size, MSG_DONTWAIT | MSG_NOSIGNAL);
        // cannot return less than size, since we're using SOCK_SEQPACKET
        err = len < 0 ? errno : 0;
    } while (err == EINTR);
    return err == 0 ? len : -err;
}

ssize_t BitTube::read(void* vaddr, size_t size)
{
    ssize_t err, len;
    do {
        len = ::recv(mReceiveFd, vaddr, size, MSG_DONTWAIT);
        err = len < 0 ? errno : 0;
    } while (err == EINTR);
    if (err == EAGAIN || err == EWOULDBLOCK) {
        // EAGAIN means that we have non-blocking I/O but there was
        // no data to be read. Nothing the client should care about.
        return 0;
    }
    return err == 0 ? len : -err;
}
// ... ...
ssize_t BitTube::sendObjects(const sp<BitTube>& tube,
        void const* events, size_t count, size_t objSize)
{
    const char* vaddr = reinterpret_cast<const char*>(events);
    ssize_t size = tube->write(vaddr, count*objSize);

    // should never happen because of SOCK_SEQPACKET
    LOG_ALWAYS_FATAL_IF((size >= 0) && (size % static_cast<ssize_t>(objSize)),
            "BitTube::sendObjects(count=%zu, size=%zu), res=%zd (partial events were sent!)",
            count, objSize, size);

    //ALOGE_IF(size<0, "error %d sending %d events", size, count);
    return size < 0 ? size : size / static_cast<ssize_t>(objSize);
}

ssize_t BitTube::recvObjects(const sp<BitTube>& tube,
        void* events, size_t count, size_t objSize)
{
    char* vaddr = reinterpret_cast<char*>(events);
    ssize_t size = tube->read(vaddr, count*objSize);

    // should never happen because of SOCK_SEQPACKET
    LOG_ALWAYS_FATAL_IF((size >= 0) && (size % static_cast<ssize_t>(objSize)),
            "BitTube::recvObjects(count=%zu, size=%zu), res=%zd (partial events were received!)",
            count, objSize, size);

    //ALOGE_IF(size<0, "error %d receiving %d events", size, count);
    return size < 0 ? size : size / static_cast<ssize_t>(objSize);
}
// ... ...
}; // namespace android

问题又又来了，哪这个 SensorService::threadLoop() 又是谁触发的？？？

SensorService::threadLoop()中connection->sendEvent 触发经过SensorEventConnection::sendEvents方法，再调用SensorEventQueue::write，实际触发 BitTube::sendObjects(tube, events, numEvents);

  请查看**SensorService启动**：device.poll 通过poll往hal层取sensor数据， 若没有数据的时候就一直阻塞（该阻塞功能由SensorHAL层实现），当有数据时该函数就会返回

本文地址：https://blog.csdn.net/qq_23452385/article/details/107888880