android6.0源码分析之Camera API1.0初始化

1、CameraService的注册

在ServiceManager的初始化过程中，会启动MediaService进程，而在MediaService进程中会初始化一系列的服务，这其中就包括CameraService.

int main(int argc __unused, char** argv)
{
    ...
    sp<ProcessState> proc(ProcessState::self());
    sp<IServiceManager> sm = defaultServiceManager();
    AudioFlinger::instantiate();
    MediaPlayerService::instantiate();
    ResourceManagerService::instantiate();
    CameraService::instantiate();
    AudioPolicyService::instantiate();
    SoundTriggerHwService::instantiate();
    RadioService::instantiate();
    registerExtensions();
    ProcessState::self()->startThreadPool();
    IPCThreadState::self()->joinThreadPool();
}

在MediaServer的main方法中，会调用CameraService的instantiate方法来进行CameraService的注册。继续分析instantiate方法：

static void instantiate() { 
    publish();
}

instantiate调用了publish()方法，继续看publish()方法：

public:
    static status_t publish(bool allowIsolated = false) {
        sp<IServiceManager> sm(defaultServiceManager());
        return sm->addService(String16(
                SERVICE::getServiceName()),
                new SERVICE(), allowIsolated);
    }

由此可知，此处将CameraService服务add到了ServiceManager进程中，即CameraService完成了注册。

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2、应用层初始化流程

在android6.0源码分析之Camera框架简介中已经介绍了Camera子系统的代码结构，应用层的初始化以Camera.java的onCreate方法最为入口：

@Override
public void onCreate(Bundle icicle) {
    super.onCreate(icicle);
    getPreferredCameraId();
    mFocusManager = new FocusManager(mPreferences, 
                            defaultFocusModes);
    /*To reduce startup time, we start the camera open and
         preview threads.
         We make sure the preview is started at the end of 
         onCreate.
    */
    mCameraOpenThread.start();

    ...

    // Make sure camera device is opened.
    try {
        mCameraOpenThread.join();
        mCameraOpenThread =