android 有关怎么自己添加系统级服务 java层 重点aidl

frameworks/base/core/java/android/os下面加aidl文件和frameworks/base/core/java/android/app下面加aidl文件有什么区别，不清楚

interface ICarSignalManager { 
    void setBacklightState(boolean state);
}

在frameworks/base/services/java的com.android.server下面

public class CarSignalManagerService extends ICarSignalManager.Stub {
         ......
}

在SystemServer的ServerThread的run方法中

ServiceManager.addService(Context.CAR_SIGNAL_SERVICE, new CarSignalManagerService(context));

上面的方法涉及到ServiceManager，我们这里根据那个addService来跟踪下：

    public static void addService(String name, IBinder service) {
        try {
            getIServiceManager().addService(name, service);
        } catch (RemoteException e) {
            Log.e(TAG, "error in addService", e);
        }
    }

IServiceManager的实现类：ServiceManagerNative和ServiceManagerProxy这两个又有什么区别呢？

服务调用的地方

	public CarSignalManager(Context context) {
		IBinder b = ServiceManager.getService(Context.CAR_SIGNAL_SERVICE);
		if (b == null) {
			throw new RuntimeException("Car Signal service not available!");
		}
		mService = ICarSignalManager.Stub.asInterface(b);
	}

CarSignalManager carSignalManager = (CarSignalManager) mContext
						.getSystemService(Context.CAR_SIGNAL_SERVICE);
				carSignalManager.setBacklightState(false);

ApplicationContext中

 @Override
    public Object getSystemService(String name) {

...
if (CAR_SIGNAL_SERVICE.equals(name)) {
            return getCarSignalManager();
		}
...

}