status_t SurfaceFlinger::createBufferQueueLayer(const sp<Client>& client, std::string name,
                                                uint32_t w, uint32_t h, uint32_t flags,
                                                LayerMetadata metadata, PixelFormat& format,
                                                sp<IBinder>* handle,
                                                sp<IGraphicBufferProducer>* gbp,
                                                sp<Layer>* outLayer) {
    // initialize the surfaces
    switch (format) {
    case PIXEL_FORMAT_TRANSPARENT:
    case PIXEL_FORMAT_TRANSLUCENT:
        format = PIXEL_FORMAT_RGBA_8888;
        break;
    case PIXEL_FORMAT_OPAQUE:
        format = PIXEL_FORMAT_RGBX_8888;
        break;
    }

    sp<BufferQueueLayer> layer;
    LayerCreationArgs args(this, client, std::move(name), w, h, flags, std::move(metadata));
    args.textureName = getNewTexture();
    {
        // Grab the SF state lock during this since it's the only safe way to access
        // RenderEngine when creating a BufferLayerConsumer
        // TODO: Check if this lock is still needed here
        Mutex::Autolock lock(mStateLock);
        layer = getFactory().createBufferQueueLayer(args);
    }

    status_t err = layer->setDefaultBufferProperties(w, h, format);
    if (err == NO_ERROR) {
        *handle = layer->getHandle();
        *gbp = layer->getProducer();
        *outLayer = layer;
    }

    ALOGE_IF(err, "createBufferQueueLayer() failed (%s)", strerror(-err));
    return err;
}

• 如果 format 是 PIXEL_FORMAT_TRANSPARENT 或 PIXEL_FORMAT_TRANSLUCENT，即有透明度，则使用 PIXEL_FORMAT_RGBA_8888，如果是不透明的，则使用 PIXEL_FORMAT_RGBX_8888。
• 调用 DefaultFactory 的 createBufferQueueLayer() 创建 BufferQueueLayer，它的实现是直接调用 BufferQueueLayer 构造函数。然后调用 setDefaultBufferProperties() 设置默认的宽高和像素格式。
• BufferQueueLayer 间接继承 RefBase，在 BufferQueueLayer::onFirstRef() 中创建了 BufferQueue 和生产者消费者。
• 如果没有错误，则设置 handle、gbp、outLayer。