android 5.1 camera_android5.1 camera-优快云博客

本文链接：https://blog.youkuaiyun.com/ivychend/article/details/79700884

本文详细介绍了Android系统中CameraService的启动流程，包括其在main_mediaserver.cpp中的注册过程，以及通过BinderService模板类实现的发布和服务实例化机制。

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- 1 CameraService启动流程

1 CameraService启动流程

　　android framework中多媒体相关的都在，frameworks/av/media/mediaserver/main_mediaserver.cpp注册
　　

// from LOCAL_C_INCLUDES，这个宏是在Android.mk中定义的，包含下面几个头文件的位置
#include "AudioFlinger.h"
#include "CameraService.h"
#include "MediaLogService.h"
#include "MediaPlayerService.h"
#include "AudioPolicyService.h"
#include "SoundTriggerHwService.h"
...
int main(int argc __unused, char** argv)
{
    ...
    sp<ProcessState> proc(ProcessState::self());
    sp<IServiceManager> sm = defaultServiceManager();
    ALOGI("ServiceManager: %p", sm.get());
    AudioFlinger::instantiate();
    MediaPlayerService::instantiate();
    CameraService::instantiate(); // CameraService实例化
    AudioPolicyService::instantiate();
    SoundTriggerHwService::instantiate();
    registerExtensions();
    ProcessState::self()->startThreadPool();
    IPCThreadState::self()->joinThreadPool();
    ...
}

　　在main_mediasever.cpp同目录的Android.mk中有下面代码，可知CameraService.h文件在framewoks/av/services/camera/libcameraservice目录下，两个重要文件CameraService.cpp和CameraService.h

LOCAL_C_INCLUDES := \
    frameworks/av/media/libmediaplayerservice \ 
    frameworks/av/services/medialog \
    frameworks/av/services/audioflinger \
    frameworks/av/services/audiopolicy \
    frameworks/av/services/camera/libcameraservice \
    $(call include-path-for, audio-utils) \
    frameworks/av/services/soundtrigger

　　CameraService.cpp中并没有实现instantiate( )方法，而是由其父类BinderService来实现

//CameraService.h
class CameraService : public BinderService<CameraService>,  public BnCameraService,  public IBinder::DeathRecipient,
    public camera_module_callbacks_t
{
    friend class BinderService<CameraService>;
public:
    class Client;
    class BasicClient;
...
}

//./native/include/binder/BinderService.h
template<typename SERVICE>
class BinderService
{
public:
    static status_t publish(bool allowIsolated = false) {
        sp<IServiceManager> sm(defaultServiceManager());
        return sm->addService(
                String16(SERVICE::getServiceName()),
                new SERVICE(), allowIsolated);
    }
    static void instantiate() { publish(); }