SensorManager

通过前面的博客介绍可知在Java application中，由SystemSensorManage对象管理每一个sensor；

在msm8909平台的HAL sensor实现中，有native SensorManager 管理HAL sensor 与Sensor driver交互，同时与Freamwork交互；

在它们中间即Native C/C++ Libraries中，同样也是由相应的SensorManager管理；以下是SensorManager class定义：

class SensorManager : public ASensorManager
{public:static SensorManager& getInstanceForPackage(const String16& packageName);~SensorManager();ssize_t getSensorList(Sensor const* const** list);ssize_t getDynamicSensorList(Vector<Sensor>& list);Sensor const* getDefaultSensor(int type);sp<SensorEventQueue> createEventQueue(String8 packageName = String8(""), int mode = 0);bool isDataInjectionEnabled();
private:// DeathRecipient interfacevoid sensorManagerDied();SensorManager(const String16& opPackageName);status_t assertStateLocked();
private:static Mutex sLock;static std::map<String16, SensorManager*> sPackageInstances;Mutex mLock;sp<ISensorServer> mSensorServer;Sensor const** mSensorList;Vector<Sensor> mSensors;sp<IBinder::DeathRecipient> mDeathObserver;const String16 mOpPackageName;
};

其构造器内容：

SensorManager::SensorManager(const String16& opPackageName): mSensorList(0), mOpPackageName(opPackageName) {// okay we're not locked here, but it's not needed during constructionassertStateLocked();
}

调用了 SensorManager的 assertStateLocked();

status_t SensorManager::assertStateLocked() {bool initSensorManager = false;if (mSensorServer == NULL) {initSensorManager = true;} else {// Ping binder to check if sensorservice is alive.status_t err = IInterface::asBinder(mSensorServer)->pingBinder();if (err != NO_ERROR) {initSensorManager = true;}}if (initSensorManager) {// try for 300 seconds (60*5(getService() tries for 5 seconds)) before giving up ...const String16 name("sensorservice");for (int i = 0; i < 60; i++) {status_t err = getService(name, &mSensorServer);if (err == NAME_NOT_FOUND) {sleep(1);continue;}
//......}class DeathObserver : public IBinder::DeathRecipient {SensorManager& mSensorManager;virtual void binderDied(const wp<IBinder>& who) {ALOGW("sensorservice died [%p]", who.unsafe_get());mSensorManager.sensorManagerDied();}public:DeathObserver(SensorManager& mgr) : mSensorManager(mgr) { }};LOG_ALWAYS_FATAL_IF(mSensorServer.get() == NULL, "getService(SensorService) NULL");mDeathObserver = new DeathObserver(*const_cast<SensorManager *>(this));IInterface::asBinder(mSensorServer)->linkToDeath(mDeathObserver);mSensors = mSensorServer->getSensorList(mOpPackageName);size_t count = mSensors.size();mSensorList =static_cast<Sensor const**>(malloc(count * sizeof(Sensor*)));LOG_ALWAYS_FATAL_IF(mSensorList == NULL, "mSensorList NULL");for (size_t i=0 ; i<count ; i++) {mSensorList[i] = mSensors.array() + i;}}return NO_ERROR;
}

初始化过程，获取Service：getService(name, &mSensorServer); 它的定义是 sp mSensorServer;

ISensorServer

frameworks\native\include\gui\ISensorServer.h
class ISensorServer : public IInterface
{public:DECLARE_META_INTERFACE(SensorServer);virtual Vector<Sensor> getSensorList(const String16& opPackageName) = 0;virtual Vector<Sensor> getDynamicSensorList(const String16& opPackageName) = 0;virtual sp<ISensorEventConnection> createSensorEventConnection(const String8& packageName,int mode, const String16& opPackageName) = 0;virtual int32_t isDataInjectionEnabled() = 0;
};frameworks\native\libs\gui\ISensorServer.cpp
virtual sp<ISensorEventConnection> createSensorEventConnection(const String8& packageName,int mode, const String16& opPackageName){Parcel data, reply;data.writeInterfaceToken(ISensorServer::getInterfaceDescriptor());data.writeString8(packageName);data.writeInt32(mode);data.writeString16(opPackageName);remote()->transact(CREATE_SENSOR_EVENT_CONNECTION, data, &reply);return interface_cast<ISensorEventConnection>(reply.readStrongBinder());}

Sensor JNI

在分析Java application过程中，在SystemSensorManager 使用了大量的native 方法；在android的层次架构中，想要清楚的梳理代码逻辑关系，首先还是需要

把java 和 c++ 直接的映射关系，需要分析其中jni 实现；

系统启动过程中，AndroidRuntime会注册所需要的JNI接口；在AndroidRuntime.cpp中：

代码路径：/frameworks/base/core/jni/AndroidRuntime.cpp

/** Register android native functions with the VM.*/
/*static*/ int AndroidRuntime::startReg(JNIEnv* env)
{  ATRACE_NAME("RegisterAndroidNatives");androidSetCreateThreadFunc((android_create_thread_fn) javaCreateThreadEtc);ALOGV("--- registering native functions ---\n");env->PushLocalFrame(200);if (register_jni_procs(gRegJNI, NELEM(gRegJNI), env) < 0) {//......
}
static const RegJNIRec gRegJNI[] = {//......REG_JNI(register_android_hardware_SensorManager),
//......
}

register_android_hardware_SensorManager 实现的内容：

代码路径：/frameworks/base/core/jni/android_hardware_SensorManager.cpp

int register_android_hardware_SensorManager(JNIEnv *env)
{RegisterMethodsOrDie(env, "android/hardware/SystemSensorManager",gSystemSensorManagerMethods, NELEM(gSystemSensorManagerMethods));RegisterMethodsOrDie(env, "android/hardware/SystemSensorManager$BaseEventQueue",gBaseEventQueueMethods, NELEM(gBaseEventQueueMethods));gBaseEventQueueClassInfo.clazz = FindClassOrDie(env,"android/hardware/SystemSensorManager$BaseEventQueue");
//......return 0;
}

这里只关注 RegisterMethodsOrDie 注册的gSystemSensorManagerMethods，gBaseEventQueueMethods；如其名称，前者是sensormange相关，后者是sensor event相关；主要内容如下：

static const JNINativeMethod gSystemSensorManagerMethods[] = {{"nativeClassInit","()V",(void*)nativeClassInit },{"nativeCreate","(Ljava/lang/String;)J",(void*)nativeCreate },{"nativeGetSensorAtIndex","(JLandroid/hardware/Sensor;I)Z",(void*)nativeGetSensorAtIndex },{"nativeGetDynamicSensors","(JLjava/util/List;)V",(void*)nativeGetDynamicSensors },{"nativeIsDataInjectionEnabled","(J)Z",(void*)nativeIsDataInjectionEnabled},
};

static const JNINativeMethod gBaseEventQueueMethods[] = {{"nativeInitBaseEventQueue","(JLjava/lang/ref/WeakReference;Landroid/os/MessageQueue;Ljava/lang/String;ILjava/lang/String;)J",(void*)nativeInitSensorEventQueue },{"nativeEnableSensor","(JIII)I",(void*)nativeEnableSensor },{"nativeDisableSensor","(JI)I",(void*)nativeDisableSensor },{"nativeDestroySensorEventQueue","(J)V",(void*)nativeDestroySensorEventQueue },{"nativeFlushSensor","(J)I",(void*)nativeFlushSensor },{"nativeInjectSensorData","(JI[FIJ)I",(void*)nativeInjectSensorData },
};

SystemManager.java 访问JNI

在SystemSensorManager.java中，其构造器函数会调用nativeClassInit() 用于初始化；nativeCreate用于创建SensorManager实例；调用nativeGetSensorAtIndex 循环初始化在java中的 sensor list；

代码实现如下：

    public SystemSensorManager(Context context, Looper mainLooper) {synchronized(sLock) {if (!sNativeClassInited) {sNativeClassInited = true;nativeClassInit();}}mMainLooper = mainLooper;mTargetSdkLevel = context.getApplicationInfo().targetSdkVersion;mContext = context;mNativeInstance = nativeCreate(context.getOpPackageName());// initialize the sensor listfor (int index = 0;;++index) {Sensor sensor = new Sensor();if (!nativeGetSensorAtIndex(mNativeInstance, sensor, index)) break;mFullSensorsList.add(sensor);mHandleToSensor.put(sensor.getHandle(), sensor);}}

它们在android_hardware_SensorManager.cpp 中的实现如下：

nativeClassInit

static void
nativeClassInit (JNIEnv *_env, jclass _this)
{//android.hardware.SensorSensorOffsets& sensorOffsets = gSensorOffsets;jclass sensorClass = (jclass) _env->NewGlobalRef(_env->FindClass("android/hardware/Sensor"));sensorOffsets.clazz       = sensorClass;sensorOffsets.name        = _env->GetFieldID(sensorClass, "mName",      "Ljava/lang/String;");sensorOffsets.vendor      = _env->GetFieldID(sensorClass, "mVendor",    "Ljava/lang/String;");sensorOffsets.version     = _env->GetFieldID(sensorClass, "mVersion",   "I");sensorOffsets.handle      = _env->GetFieldID(sensorClass, "mHandle",    "I");sensorOffsets.range       = _env->GetFieldID(sensorClass, "mMaxRange",  "F");sensorOffsets.resolution  = _env->GetFieldID(sensorClass, "mResolution","F");sensorOffsets.power       = _env->GetFieldID(sensorClass, "mPower",     "F");sensorOffsets.minDelay    = _env->GetFieldID(sensorClass, "mMinDelay",  "I");sensorOffsets.fifoReservedEventCount =_env->GetFieldID(sensorClass, "mFifoReservedEventCount",  "I");sensorOffsets.fifoMaxEventCount = _env->GetFieldID(sensorClass, "mFifoMaxEventCount",  "I");sensorOffsets.stringType = _env->GetFieldID(sensorClass, "mStringType", "Ljava/lang/String;");sensorOffsets.requiredPermission = _env->GetFieldID(sensorClass, "mRequiredPermission","Ljava/lang/String;");sensorOffsets.maxDelay    = _env->GetFieldID(sensorClass, "mMaxDelay",  "I");sensorOffsets.flags = _env->GetFieldID(sensorClass, "mFlags",  "I");sensorOffsets.setType = _env->GetMethodID(sensorClass, "setType", "(I)Z");sensorOffsets.setUuid = _env->GetMethodID(sensorClass, "setUuid", "(JJ)V");sensorOffsets.init = _env->GetMethodID(sensorClass, "<init>", "()V");// java.util.List;ListOffsets& listOffsets = gListOffsets;jclass listClass = (jclass) _env->NewGlobalRef(_env->FindClass("java/util/List"));listOffsets.clazz = listClass;listOffsets.add = _env->GetMethodID(listClass, "add", "(Ljava/lang/Object;)Z");
}

nativeCreate

static jlong nativeCreate
(JNIEnv *env, jclass clazz, jstring opPackageName)
{ScopedUtfChars opPackageNameUtf(env, opPackageName);return (jlong) &SensorManager::getInstanceForPackage(String16(opPackageNameUtf.c_str()));
}

在JNI绑定的 nativeCreate中，调用了用于创建SensorManager的实例化接口；

nativeGetSensorAtIndex

static jboolean
nativeGetSensorAtIndex(JNIEnv *env, jclass clazz, jlong sensorManager, jobject sensor, jint index)
{SensorManager* mgr = reinterpret_cast<SensorManager*>(sensorManager);Sensor const* const* sensorList;ssize_t count = mgr->getSensorList(&sensorList);if (ssize_t(index) >= count) {return false;}return translateNativeSensorToJavaSensor(env, sensor, *sensorList[index]) != NULL;
}

在函数的最后调用了translateNativeSensorToJavaSensor，这正是前面提到的把C++ 中的sensor 结构转化为java中的Sensor结构，它的实现如下：

translateNativeSensorToJavaSensor

translateNativeSensorToJavaSensor(JNIEnv *env, jobject sensor, const Sensor& nativeSensor) {const SensorOffsets& sensorOffsets(gSensorOffsets);if (sensor == NULL) {// Sensor sensor = new Sensor();sensor = env->NewObject(sensorOffsets.clazz, sensorOffsets.init, "");}if (sensor != NULL) {jstring name = env->NewStringUTF(nativeSensor.getName().string());jstring vendor = env->NewStringUTF(nativeSensor.getVendor().string());jstring requiredPermission =env->NewStringUTF(nativeSensor.getRequiredPermission().string());env->SetObjectField(sensor, sensorOffsets.name,      name);env->SetObjectField(sensor, sensorOffsets.vendor,    vendor);env->SetIntField(sensor, sensorOffsets.version,      nativeSensor.getVersion());env->SetIntField(sensor, sensorOffsets.handle,       nativeSensor.getHandle());env->SetFloatField(sensor, sensorOffsets.range,      nativeSensor.getMaxValue());env->SetFloatField(sensor, sensorOffsets.resolution, nativeSensor.getResolution());env->SetFloatField(sensor, sensorOffsets.power,      nativeSensor.getPowerUsage());env->SetIntField(sensor, sensorOffsets.minDelay,     nativeSensor.getMinDelay());env->SetIntField(sensor, sensorOffsets.fifoReservedEventCount,nativeSensor.getFifoReservedEventCount());env->SetIntField(sensor, sensorOffsets.fifoMaxEventCount,nativeSensor.getFifoMaxEventCount());env->SetObjectField(sensor, sensorOffsets.requiredPermission,requiredPermission);env->SetIntField(sensor, sensorOffsets.maxDelay, nativeSensor.getMaxDelay());env->SetIntField(sensor, sensorOffsets.flags, nativeSensor.getFlags());if (env->CallBooleanMethod(sensor, sensorOffsets.setType, nativeSensor.getType())== JNI_FALSE) {jstring stringType = getInternedString(env, &nativeSensor.getStringType());env->SetObjectField(sensor, sensorOffsets.stringType, stringType);}// TODO(b/29547335): Rename "setUuid" method to "setId".int64_t id = nativeSensor.getId();env->CallVoidMethod(sensor, sensorOffsets.setUuid, id, 0);}return sensor;
}

SensorManager实例化

通过上面内容可知，systemSensosrManager.java中调用了nativeCreate，会调用到 JNI中绑定的nativeCreate，进而调用SensorManager 实例化的api：

(jlong) &SensorManager::getInstanceForPackage(String16(opPackageNameUtf.c_str()));

它的实例化过程如下：

getInstanceForPackage

SensorManager& SensorManager::getInstanceForPackage(const String16& packageName) {Mutex::Autolock _l(sLock);SensorManager* sensorManager;std::map<String16, SensorManager*>::iterator iterator =sPackageInstances.find(packageName);if (iterator != sPackageInstances.end()) {sensorManager = iterator->second;} else {String16 opPackageName = packageName;if (opPackageName.size() <= 0) {sp<IBinder> binder = defaultServiceManager()->getService(String16("permission"));if (binder != 0) {const uid_t uid = IPCThreadState::self()->getCallingUid();Vector<String16> packages;interface_cast<IPermissionController>(binder)->getPackagesForUid(uid, packages);if (!packages.isEmpty()) {opPackageName = packages[0];} else {ALOGE("No packages for calling UID");}} else {ALOGE("Cannot get permission service");}}sensorManager = new SensorManager(opPackageName);if (packageName.size() <= 0) {sPackageInstances.insert(std::make_pair(String16(), sensorManager));}// Stash the per package sensor manager.sPackageInstances.insert(std::make_pair(opPackageName, sensorManager));}return *sensorManager;
}

SensorEvent

整理中…

时序图

在app启动加载之前，启动初始化时已经创建了SensorMangager; 通过JNI绑定了 SensorManager的相应native方法，以下是其简要步骤；

a: AndroidRuntime::start() ->REG_JNI(register_android_hardware_SensorManager)
./base/core/jni/AndroidRuntime.cpp中调用注册了本地C++ 方法，库文件是libandroid_runtime.so；
详细过程参考：Android系统启动流程
b: android_hardware_SensorManager.cpp中完成native C++函数与java方法的绑定，RegisterMethods；
c: 上面过程中已经完成了加载，Java代码中SystemSensorManager可以直接调用Sensor相关的native方法；
A: 系统服务注册时会创建SensorManager；
代码路径：./core/java/android/app/SystemServiceRegistry.java
registerService(Context.SENSOR_SERVICE, SensorManager.class,
new CachedServiceFetcher() {
@Override
public SensorManager createService(ContextImpl ctx) {
return new SystemSensorManager(ctx.getOuterContext(),
ctx.mMainThread.getHandler().getLooper());
}});
参考：android笔记之SystemServiceRegistry
B: 创建一个SystemSensorManger实例；其构造函数会调用本地方法： nativeClassInit();
C: 构造函数会调用本地方法： nativeCreate(context.getOpPackageName());
D: 调用：nativeGetSensorAtIndex 循环添加sensor；

App中，MainActivity中获取SensorManager；
通过SensorManager 获取类型为Acc的sensor对象；
通过SensorManager.registerListener注册SensorEventListener监听器，监听传感器
registerListener调用到registerListenerImpl会创建SensorEventQueue，继承自BaseEventQueue ；
通过JNI调用本地方法nativeInitBaseEventQueue；
C++中绑定的nativeInitSensorEventQueue函数被调用；创建event队列createEventQueue
添加Receiver；
addSensor将sensor添加到queue，addSensorEvent(sensor);；
addSensor使能sensor，通过JNI调用到本地方法：nativeEnableSensor；
调用enable

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