前言

我们接着androidP Surface到SurfaceFlinger --＞创建Surface （一）来看，当new SurfaceControl之后在其构造函数内都做了什么？这一步跟下去就到了SurfaceFlinger了。

SurfaceFlinger createLayer

对于上层应用所建立的Surface对应到SurfaceFlinger 就是 createLayer
我们来跟代码吧，还是从 SurfaceControl的构造函数开始

  private SurfaceControl(SurfaceSession session, String name, int w, int h, int format, int flags,
            SurfaceControl parent, int windowType, int ownerUid)
                    throws OutOfResourcesException, IllegalArgumentException {
        if (session == null) {
            throw new IllegalArgumentException("session must not be null");
        }
        if (name == null) {
            throw new IllegalArgumentException("name must not be null");
        }

        if ((flags & SurfaceControl.HIDDEN) == 0) {
            Log.w(TAG, "Surfaces should always be created with the HIDDEN flag set "
                    + "to ensure that they are not made visible prematurely before "
                    + "all of the surface's properties have been configured.  "
                    + "Set the other properties and make the surface visible within "
                    + "a transaction.  New surface name: " + name,
                    new Throwable());
        }

        mName = name;
        mWidth = w;
        mHeight = h;
        // 这里传进去的参数有，session这个是session就是持有该SurfaceControl的SurfaceSession对象，
        // name 就是window的名字
        // w，h window的宽和高
        // format 设置的view的格式
        // windowType window的类型，就是层级吧
        // ownerUid 创建的app的uid
        mNativeObject = nativeCreate(session, name, w, h, format, flags,
            parent != null ? parent.mNativeObject : 0, windowType, ownerUid);
	... ...
    }

frameworks/base/core/jni/android_view_SurfaceControl.cpp

static jlong nativeCreate(JNIEnv* env, jclass clazz, jobject sessionObj,
        jstring nameStr, jint w, jint h, jint format, jint flags, jlong parentObject,
        jint windowType, jint ownerUid) {
    ScopedUtfChars name(env, nameStr);
    // 前面我们知道已经创建过连接了，在new SurfaceSession的就持有了SurfaceComposerClient的对象这个直接用就可以了
    sp<SurfaceComposerClient> client(android_view_SurfaceSession_getClient(env, sessionObj));
    SurfaceControl *parent = reinterpret_cast<SurfaceControl*>(parentObject);
    sp<SurfaceControl> surface;
    // 调用 SurfaceComposerClient的createSurfaceChecked方法
    status_t err = client->createSurfaceChecked(
            String8(name.c_str()), w, h, format, &surface, flags, parent, windowType, ownerUid);
    if (err == NAME_NOT_FOUND) {
        jniThrowException(env, "java/lang/IllegalArgumentException", NULL);
        return 0;
    } else if (err != NO_ERROR) {
        jniThrowException(env, OutOfResourcesException, NULL);
        return 0;
    }

    surface->incStrong((void *)nativeCreate);
    return reinterpret_cast<jlong>(surface.get());
}

status_t SurfaceComposerClient::createSurfaceChecked(
        const String8& name,
        uint32_t w,
        uint32_t h,
        PixelFormat format,
        sp<SurfaceControl>* outSurface,
        uint32_t flags,
        SurfaceControl* parent,
        int32_t windowType,
        int32_t ownerUid)
{
    sp<SurfaceControl> sur;
    status_t err = mStatus;

    if (mStatus == NO_ERROR) {
        sp<IBinder> handle;
        sp<IBinder> parentHandle;
        // 注意哈，这里出现了IGraphicBufferProducer，生产者BufferQueueProducer的父类
        sp<IGraphicBufferProducer> gbp;

        if (parent != nullptr) {
            parentHandle = parent->getHandle();
        }
		
		// gbp取地址给了createSurface，那一般就是要给gbp分配地址了，这个client就是ISurfaceComposerClient的本地实现类。
        err = mClient->createSurface(name, w, h, format, flags, parentHandle,
                windowType, ownerUid, &handle, &gbp);
        ALOGE_IF(err, "SurfaceComposerClient::createSurface error %s", strerror(-err));
        if (err == NO_ERROR) {
            *outSurface = new SurfaceControl(this, handle, gbp, true /* owned */);
        }
    }
    return err;
}

frameworks/native/services/surfaceflinger/Client.cpp

status_t Client::createSurface(
        const String8& name,
        uint32_t w, uint32_t h, PixelFormat format, uint32_t flags,
        const sp<IBinder>& parentHandle, int32_t windowType, int32_t ownerUid,
        sp<IBinder>* handle,
        sp<IGraphicBufferProducer>* gbp)
{
    sp<Layer> parent = nullptr;
    if (parentHandle != nullptr) {
        auto layerHandle = reinterpret_cast<Layer::Handle*>(parentHandle.get());
        parent = layerHandle->owner.promote();
        if (parent == nullptr) {
            return NAME_NOT_FOUND;
        }
    }
    if (parent == nullptr) {
        bool parentDied;
        parent = getParentLayer(&parentDied);
        // If we had a parent, but it died, we've lost all
        // our capabilities.
        if (parentDied) {
            return NAME_NOT_FOUND;
        }
    }

	// 继续跟到SurfaceFlinger里面
    return mFlinger->createLayer(name, this, w, h, format, flags, windowType,
                                 ownerUid, handle, gbp, &parent);
}

frameworks/native/services/surfaceflinger/SurfaceFlinger.cpp

//从createSurface到了createLayer
status_t SurfaceFlinger::createLayer(
        const String8& name,
        const sp<Client>& client,
        uint32_t w, uint32_t h, PixelFormat format, uint32_t flags,
        int32_t windowType, int32_t ownerUid, sp<IBinder>* handle,
        sp<IGraphicBufferProducer>* gbp, sp<Layer>* parent)
{
    if (int32_t(w|h) < 0) {
        ALOGE("createLayer() failed, w or h is negative (w=%d, h=%d)",
                int(w), int(h));
        return BAD_VALUE;
    }

    ALOGE("createLayer() -> name = %s, windowType = %d",
                name.c_str(), windowType);
    status_t result = NO_ERROR;

    sp<Layer> layer;

    String8 uniqueName = getUniqueLayerName(name);

	// 该函数中根据flag创建不同的Layer，Layer前面说过了就是一个图层
    switch (flags & ISurfaceComposerClient::eFXSurfaceMask) {
        case ISurfaceComposerClient::eFXSurfaceNormal:
        // 创建了BufferLayer
            result = createBufferLayer(client,
                    uniqueName, w, h, flags, format,
                    handle, gbp, &layer);

            break;
        case ISurfaceComposerClient::eFXSurfaceColor:
            result = createColorLayer(client,
                    uniqueName, w, h, flags,
                    handle, &layer);
            break;
        default:
            result = BAD_VALUE;
            break;
    }

    if (result != NO_ERROR) {
        return result;
    }

    // window type is WINDOW_TYPE_DONT_SCREENSHOT from SurfaceControl.java
    // TODO b/64227542
    if (windowType == 441731) {
        windowType = 2024; // TYPE_NAVIGATION_BAR_PANEL
        layer->setPrimaryDisplayOnly();
    }

    layer->setInfo(windowType, ownerUid);

    result = addClientLayer(client, *handle, *gbp, layer, *parent);
    if (result != NO_ERROR) {
        return result;
    }
    mInterceptor->saveSurfaceCreation(layer);

    setTransactionFlags(eTransactionNeeded);
    return result;
}

status_t SurfaceFlinger::createBufferLayer(const sp<Client>& client,
        const String8& name, uint32_t w, uint32_t h, uint32_t flags, 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;
    }
	
	// 创建出了一个BufferLayer，这个BufferLayer里面回去创建BufferCore
    sp<BufferLayer> layer = new BufferLayer(this, client, name, w, h, flags);
    status_t err = layer->setBuffers(w, h, format, flags);
    if (err == NO_ERROR) {
        *handle = layer->getHandle();
        *gbp = layer->getProducer();
        *outLayer = layer;
    }

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

BufferLayer被new出来的时候会走进它的onFirstRef()方法里面

void BufferLayer::onFirstRef() {
    Layer::onFirstRef();

    // Creates a custom BufferQueue for SurfaceFlingerConsumer to use
    sp<IGraphicBufferProducer> producer;
    sp<IGraphicBufferConsumer> consumer;
    // 在这里面会给producer 和 consumer进行赋值
    BufferQueue::createBufferQueue(&producer, &consumer, true);
    mProducer = new MonitoredProducer(producer, mFlinger, this);
    {
        // Grab the SF state lock during this since it's the only safe way to access RenderEngine
        Mutex::Autolock lock(mFlinger->mStateLock);
        mConsumer = new BufferLayerConsumer(consumer, mFlinger->getRenderEngine(), mTextureName,
                                            this);
    }
    mConsumer->setConsumerUsageBits(getEffectiveUsage(0));
    mConsumer->setContentsChangedListener(this);
    mConsumer->setName(mName);

    if (mFlinger->isLayerTripleBufferingDisabled()) {
        mProducer->setMaxDequeuedBufferCount(2);
    }

    const sp<const DisplayDevice> hw(mFlinger->getDefaultDisplayDevice());
    updateTransformHint(hw);
}

void BufferQueue::createBufferQueue(sp<IGraphicBufferProducer>* outProducer,
        sp<IGraphicBufferConsumer>* outConsumer,
        bool consumerIsSurfaceFlinger) {
    LOG_ALWAYS_FATAL_IF(outProducer == NULL,
            "BufferQueue: outProducer must not be NULL");
    LOG_ALWAYS_FATAL_IF(outConsumer == NULL,
            "BufferQueue: outConsumer must not be NULL");

    sp<BufferQueueCore> core(new BufferQueueCore());
    LOG_ALWAYS_FATAL_IF(core == NULL,
            "BufferQueue: failed to create BufferQueueCore");
	// 给producer进行了赋值
    sp<IGraphicBufferProducer> producer(new BufferQueueProducer(core, consumerIsSurfaceFlinger));
    LOG_ALWAYS_FATAL_IF(producer == NULL,
            "BufferQueue: failed to create BufferQueueProducer");
    // 给consumer进行了赋值
    sp<IGraphicBufferConsumer> consumer(new BufferQueueConsumer(core));
    LOG_ALWAYS_FATAL_IF(consumer == NULL,
            "BufferQueue: failed to create BufferQueueConsumer");
	// 其实我们交接buffer的操作流程都知道，这里producer是应用用来承载数据的，consumer是surfaceFlinger用来消费数据的
    *outProducer = producer;
    *outConsumer = consumer;
}

后续会接上BufferQueue的交互流程。