高通camera架构 （三） .

四 android_hardware_Camera_setPreviewDisplay（JNI）

这个接口函数的作用是为Preview分配内存。

static void android_hardware_Camera_setPreviewDisplay(JNIEnv *env, jobject thiz, jobject jSurface)
{
    LOGV("setPreviewDisplay");
    sp<Camera> camera = get_native_camera(env, thiz, NULL);
    if (camera == 0) return;

    sp<Surface> surface = NULL;
    if (jSurface != NULL) {
        surface = reinterpret_cast<Surface*>(env->GetIntField(jSurface, fields.surface));
    }
    if (camera->setPreviewDisplay(surface) != NO_ERROR) {
        jniThrowException(env, "java/io/IOException", "setPreviewDisplay failed");
    }
}

 

在camera.cpp中；

status_t Camera::setPreviewDisplay(const sp<Surface>& surface)
{
    LOGV("setPreviewDisplay");
    sp <ICamera> c = mCamera;
    if (c == 0) return NO_INIT;
    if (surface != 0) {
        return c->setPreviewDisplay(surface->getISurface());
    } else {
        LOGD("app passed NULL surface");
        return c->setPreviewDisplay(0);
    }
}

这里跳到cameraservice.cpp 中。

status_t CameraService::Client::setPreviewDisplay(const sp<ISurface>& surface) {
    LOG1("setPreviewDisplay(%p) (pid %d)", surface.get(), getCallingPid());
    Mutex::Autolock lock(mLock);
    status_t result = checkPidAndHardware();
    if (result != NO_ERROR) return result;

    result = NO_ERROR;

    // return if no change in surface.
    // asBinder() is safe on NULL (returns NULL)
    if (surface->asBinder() == mSurface->asBinder()) {
        return result;
    }

    if (mSurface != 0) {
        LOG1("clearing old preview surface %p", mSurface.get());
        if (mUseOverlay) {
            // Force the destruction of any previous overlay
            sp<Overlay> dummy;
            mHardware->setOverlay(dummy);
            mOverlayRef = 0;
        } else {
            mSurface->unregisterBuffers();
        }
    }
    mSurface = surface;
    mOverlayRef = 0;
    // If preview has been already started, set overlay or register preview
    // buffers now.
    if (mHardware->previewEnabled() || mUseOverlay) {
        if (mUseOverlay) {
            if( mSurface != NULL)
                result = setOverlay(); //创建、初始化overlay

//在实际中对这些Surface 进行merge 可以采用两种方式，一种就是采用软件的形式来merge ，还一种就是采用硬件的方式，软件的方式就是我们的SurfaceFlinger ，而硬件的方式就是Overlay
        } else if (mSurface != 0) {
            result = registerPreviewBuffers();  //注册preview buffer
        }
    }

    return result;
}