Android进阶之路Android技术进阶Android开发经验谈

车载技术开发—{Android CarFrameWork}

2023-02-19  本文已影响0人  谁动了我的代码

Android Automotive平台

Android Automotive是通过Android的通用框架，语言和API来实现的一个全栈，开源，高度可定制的平台。

Android Automotive与整个Android生态系统的关系

Android Automotive架构

image.png

Automotive

Android Automative是在原先Android的系统架构上增加了一些与车相关的（图中虚线框中绿色背景的）模块。

Android CarAPI

CarAPI

· annotation：包含了两个注解。 · app · menu：车辆应用菜单相关API。 · cluster：仪表盘相关API。 · render：渲染相关API。 · content · pm：应用包相关API。 · diagnostic：包含与汽车诊断相关的API。 · hardware：车辆硬件相关API。 · cabin：座舱相关API。 · hvac：通风空调相关API。 · property：属性相关API(实现定制的property)。 · radio：收音机相关API。 · input：输入相关API。 · media：多媒体相关API。 · navigation：导航相关API。 · settings：设置相关API。 · vms：汽车监测相关API

这些api集合中，我们可以通过CarpropertyManager去实现定制的property功能，简要类图：


CarpropertyManager内部方法

CarpropertyManager与service层交互的AIDL接口

需要注意的是ICarProperty是同步接口，ICarPropertyEventListener是异步接口。

onEvent传上来的是参数是CarPropertyEvent的list，CarPropertyEvent中包含event type与CarPropertyValue; eventType包含PROPERTY_EVENT_PROPERTY_CHANGE与PROPERTY_EVENT_ERROR，分别对应listener中的onPropertyChanged和PROPERTY_EVENT_ERROR， CarPropertyValue则包含具体的propId、propValue等具体属性信息。

Android CarService

代码目录： packages/services/Car/service

CarService启动流程

image

启动CarServiceHelperService

SystemServer启动过程中，在ActivityManagerService systemReady时，启动CarServiceHelperService。 代码：

android/frameworks/base/services/java/com/android/server/SystemServer.java

if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_AUTOMOTIVE)) {
    t.traceBegin("StartCarServiceHelperService");
    final SystemService cshs = mSystemServiceManager
            .startService(CAR_SERVICE_HELPER_SERVICE_CLASS);
    if (cshs instanceof Dumpable) {
        mDumper.addDumpable((Dumpable) cshs);
    }
    if (cshs instanceof DevicePolicySafetyChecker) {
        dpms.setDevicePolicySafetyChecker((DevicePolicySafetyChecker) cshs);
    }
    t.traceEnd();
}

private static final String CAR_SERVICE_HELPER_SERVICE_CLASS =
        "com.android.internal.car.CarServiceHelperService";

启动CarService

CarServiceHelperService在onStart时拉起CarServcie，加载Native库car-framework-service-jni。

代码：

android/frameworks/opt/car/services/src/com/android/internal/car/CarServiceHelperService.java

public void onStart() {
    EventLog.writeEvent(EventLogTags.CAR_HELPER_START);

    IntentFilter filter = new IntentFilter(Intent.ACTION_REBOOT);
    filter.addAction(Intent.ACTION_SHUTDOWN);
    mContext.registerReceiverForAllUsers(mShutdownEventReceiver, filter, null, null);
    mCarWatchdogDaemonHelper.addOnConnectionChangeListener(mConnectionListener);
    mCarWatchdogDaemonHelper.connect();
    Intent intent = new Intent();
    intent.setPackage("com.android.car");
    intent.setAction(CAR_SERVICE_INTERFACE);
    if (!mContext.bindServiceAsUser(intent, mCarServiceConnection, Context.BIND_AUTO_CREATE,
            mHandler, UserHandle.SYSTEM)) {
        Slogf.wtf(TAG, "cannot start car service");
    }
    loadNativeLibrary();
}

void loadNativeLibrary() {
    System.loadLibrary("car-framework-service-jni");
}

代码：

android/packages/services/Car/car-lib/src/com/android/car/internal/common/CommonConstants.java

public static final String CAR_SERVICE_INTERFACE = "android.car.ICar";

代码：

android/packages/services/Car/service/AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:androidprv="http://schemas.android.com/apk/prv/res/android"
     package="com.android.car"
     coreApp="true"
     android:sharedUserId="android.uid.system">

    <application android:label="@string/app_title"
         android:directBootAware="true"
         android:allowBackup="false"
         android:persistent="true">
    
        <service android:name=".CarService"
             android:singleUser="true"
             android:exported="true">
            <intent-filter>
                <action android:name="android.car.ICar"/>
            </intent-filter>
        </service>

初始化ICarImpl

CarService在onCreate时先判断Vehicle HAL起来了，然后再初始化ICarImpl。 代码：

android/packages/services/Car/service/src/com/android/car/CarService.java

public void onCreate() {
    LimitedTimingsTraceLog initTiming = new LimitedTimingsTraceLog(CAR_SERVICE_INIT_TIMING_TAG,
            Trace.TRACE_TAG_SYSTEM_SERVER, CAR_SERVICE_INIT_TIMING_MIN_DURATION_MS);
    initTiming.traceBegin("CarService.onCreate");

    initTiming.traceBegin("getVehicle");
    mVehicle = getVehicle();
    initTiming.traceEnd();
    
    EventLog.writeEvent(EventLogTags.CAR_SERVICE_CREATE, mVehicle == null ? 0 : 1);
    
    if (mVehicle == null) {
        throw new IllegalStateException("Vehicle HAL service is not available.");
    }
    try {
        mVehicleInterfaceName = mVehicle.interfaceDescriptor();
    } catch (RemoteException e) {
        throw new IllegalStateException("Unable to get Vehicle HAL interface descriptor", e);
    }
    
    Slog.i(CarLog.TAG_SERVICE, "Connected to " + mVehicleInterfaceName);
    EventLog.writeEvent(EventLogTags.CAR_SERVICE_CONNECTED, mVehicleInterfaceName);
    
    mICarImpl = new ICarImpl(this,
            mVehicle,
            SystemInterface.Builder.defaultSystemInterface(this).build(),
            mVehicleInterfaceName);
    mICarImpl.init();
    
    linkToDeath(mVehicle, mVehicleDeathRecipient);
    
    ServiceManager.addService("car_service", mICarImpl);
    SystemProperties.set("boot.car_service_created", "1");
    
    super.onCreate();
    
    initTiming.traceEnd(); // "CarService.onCreate"
}

private static IVehicle getVehicle() {
    final String instanceName = SystemProperties.get("ro.vehicle.hal", "default");

    try {
        return android.hardware.automotive.vehicle.V2_0.IVehicle.getService(instanceName);
    } catch (RemoteException e) {
        Slog.e(CarLog.TAG_SERVICE, "Failed to get IVehicle/" + instanceName + " service", e);
    } catch (NoSuchElementException e) {
        Slog.e(CarLog.TAG_SERVICE, "IVehicle/" + instanceName + " service not registered yet");
    }
    return null;
}

代码：

android/packages/services/Car/car-lib/src/android/car/ICar.aidl
android/packages/services/Car/service/src/com/android/car/ICarImpl.java

初始化各个Car Services组件

ICarImpl构造函数中，构造了下面几个实现了CarServiceBase接口的Car Services组件，以及VehicleHal和CarStatsService；然后通过init函数进行初始化。

CarFeatureController
CarPropertyService
CarDrivingStateService
CarUxRestrictionsManagerService
CarUserService
CarOccupantZoneService
SystemActivityMonitoringService
CarPowerManagementService
CarUserNoticeService
CarPackageManagerService
PerUserCarServiceHelper
CarBluetoothService
CarInputService
CarProjectionService
GarageModeService
AppFocusService
CarAudioService
CarNightService
FixedActivityService
ClusterNavigationService
InstrumentClusterService
VmsBrokerService
CarDiagnosticService
CarStorageMonitoringService
CarLocationService
CarMediaService
CarBugreportManagerService
CarExperimentalFeatureServiceController
CarWatchdogService
CarDevicePolicyService
ClusterHomeService
CarEvsService
CarTelemetryService
CarActivityService

初始化各个Hal Services组件

VehicleHal构造函数中，构造了下面几个继承自HalServiceBase基类的Hal Services组件以及HalClient；然后通过init函数进行初始化。

PowerHalService
PropertyHalService
InputHalService
VmsHalService
UserHalService
DiagnosticHalService
ClusterHalService
EvsHalService
TimeHalService

代码：

android/packages/services/Car/service/src/com/android/car/hal/VehicleHal.java

VehicleHAL目录结构

下面是vehicle 2.0参考实现的目录结构。

android/hardware/interfaces/automotive/vehicle/2.0/
|-- default // 默认实现
    |-- common
        |-- include
            |-- vhal_v2_0 // .h
        |-- src // .cpp
    |-- impl
        |-- vhal_v2_0 // impl代码
            |-- proto // proto协议
            |-- tests
    |-- tests
    |-- Android.bp // 编译文件
    |-- VehicleService.cpp // main函数
    |-- android.hardware.automotive.vehicle@2.0-service.rc // init rc
    |-- android.hardware.automotive.vehicle@2.0-service.xml // matrix xml
|-- utils
|-- vts
|-- Android.bp // 编译文件
|-- IVehicle.hal // interface
|-- IVehicleCallback.hal // callback
|-- types.hal // types

Hidl代码有个明显的namespace规则，如下。

namespace android {
namespace hardware {
namespace automotive {
namespace vehicle {
namespace V2_0 {
// ...
}  // namespace V2_0
}  // namespace vehicle
}  // namespace automotive
}  // namespace hardware
}  // namespace android

VehicleHAL启动流程

rc

VehicleHAL由init rc启动。 代码：

android/hardware/interfaces/automotive/vehicle/2.0/default/android.hardware.automotive.vehicle@2.0-service.rc

service vendor.vehicle-hal-2.0 /vendor/bin/hw/android.hardware.automotive.vehicle@2.0-service
    class early_hal
    user vehicle_network
    group system inet

main

下面是VehicleHAL的main函数。 代码：

android/hardware/interfaces/automotive/vehicle/2.0/default/VehicleService.cpp

int main(int /* argc */, char* /* argv */ []) {
    auto store = std::make_unique<VehiclePropertyStore>();
    auto connector = std::make_unique<impl::EmulatedVehicleConnector>();
    auto userHal = connector->getEmulatedUserHal();
    auto hal = std::make_unique<impl::EmulatedVehicleHal>(store.get(), connector.get(), userHal);
    auto emulator = std::make_unique<impl::VehicleEmulator>(hal.get());
    auto service = std::make_unique<VehicleHalManager>(hal.get());
    connector->setValuePool(hal->getValuePool());

    configureRpcThreadpool(4, true /* callerWillJoin */);
    
    ALOGI("Registering as service...");
    status_t status = service->registerAsService();
    
    if (status != OK) {
        ALOGE("Unable to register vehicle service (%d)", status);
        return 1;
    }
    
    ALOGI("Ready");
    joinRpcThreadpool();
    
    return 1;
}
image

以上为车机开发技术中的CarFrameWork学习；启动流程及原理介绍，更多的车载技术可以前往《车机开发技术手册》查看更多车载技术。

交互

CarService向上与App通过CarLib（aidl）交互，向下与VehicleHAL通过hidl交互，其中包括了一个很重要的概念：Property。 Property可以是静态的，也可以是变化后向上通报的，还可以是以一定的频率实时上报的。 下面以HVAC为例，说明HVAC的控制过程。

最终，将Property或转换后的信号发到【Car ECU】。vehicle 2.0模拟实现是将Property存储到VehiclePropertyStore

上一篇 下一篇

猜你喜欢

热点阅读