Android绘制系统(1): Surface - clarkehe/Android GitHub Wiki

class Surface
    : public ANativeObjectBase<ANativeWindow, Surface, RefBase>
{
public:
...

    private boolean drawSoftware(Surface surface, AttachInfo attachInfo, int xoff, int yoff,
            boolean scalingRequired, Rect dirty) {

        // Draw with software renderer.
        final Canvas canvas;
        try {
            canvas = mSurface.lockCanvas(dirty);
        } 
        ...
        try {
            ...
            try {
                ...
                mView.draw(canvas);
            }
            ....
        } finally {
            try {
                surface.unlockCanvasAndPost(canvas);
            } 
            ...
        }
        return true;
    }

    /* called from android_view_Surface_createFromIGraphicBufferProducer() */
    private Surface(long nativeObject) {
        synchronized (mLock) {
            setNativeObjectLocked(nativeObject);
        }
    }

jobject android_view_Surface_createFromIGraphicBufferProducer(JNIEnv* env,
        const sp<IGraphicBufferProducer>& bufferProducer) {
    if (bufferProducer == NULL) {
        return NULL;
    }
     
    //Native层Surface的创建，构造参数有一个非常关键的：bufferProducer
    sp<Surface> surface(new Surface(bufferProducer, true));
    if (surface == NULL) {
        return NULL;
    }

    //调用JAVA层Surface的构造方法，Java层的Surface只是一个壳，通过一个long型值引用Native层的Surface
    jobject surfaceObj = env->NewObject(gSurfaceClassInfo.clazz,
            gSurfaceClassInfo.ctor, (jlong)surface.get());
    if (surfaceObj == NULL) {
        if (env->ExceptionCheck()) {
            ALOGE("Could not create instance of Surface from IGraphicBufferProducer.");
            LOGE_EX(env);
            env->ExceptionClear();
        }
        return NULL;
    }
    surface->incStrong(&sRefBaseOwner);
    return surfaceObj;
}

    /**
     * Copy another surface to this one.  This surface now holds a reference
     * to the same data as the original surface, and is -not- the owner.
     * This is for use by the window manager when returning a window surface
     * back from a client, converting it from the representation being managed
     * by the window manager to the representation the client uses to draw
     * in to it.
     * @hide
     */
    public void copyFrom(SurfaceControl other) {
        if (other == null) {
            throw new IllegalArgumentException("other must not be null");
        }

        long surfaceControlPtr = other.mNativeObject;
        if (surfaceControlPtr == 0) {
            throw new NullPointerException(
                    "SurfaceControl native object is null. Are you using a released SurfaceControl?");
        }
        long newNativeObject = nativeCreateFromSurfaceControl(surfaceControlPtr);

        synchronized (mLock) {
            if (mNativeObject != 0) {
                nativeRelease(mNativeObject);
            }
            setNativeObjectLocked(newNativeObject);
        }
    }

    public Surface(SurfaceTexture surfaceTexture) {
        if (surfaceTexture == null) {
            throw new IllegalArgumentException("surfaceTexture must not be null");
        }

        synchronized (mLock) {
            mName = surfaceTexture.toString();
            setNativeObjectLocked(nativeCreateFromSurfaceTexture(surfaceTexture));
        }
    }

    /**
     * Construct a new SurfaceTexture to stream images to a given OpenGL texture.
     *
     * @param texName the OpenGL texture object name (e.g. generated via glGenTextures)
     *
     * @throws Surface.OutOfResourcesException If the SurfaceTexture cannot be created.
     */
    public SurfaceTexture(int texName) {
        this(texName, false);
    }

Surface::Surface(
        const sp<IGraphicBufferProducer>& bufferProducer,
        bool controlledByApp)
    : mGraphicBufferProducer(bufferProducer)
{
    // Initialize the ANativeWindow function pointers.
    ...
}

static void ImageReader_init(JNIEnv* env, jobject thiz, jobject weakThiz,
                             jint width, jint height, jint format, jint maxImages)
{
    ....


    //创建缓存队列，一个队列，一个生产者，一个消费者
    sp<IGraphicBufferProducer> gbProducer;
    sp<IGraphicBufferConsumer> gbConsumer;
    BufferQueue::createBufferQueue(&gbProducer, &gbConsumer);

    //消费者
    sp<CpuConsumer> consumer = new CpuConsumer(gbConsumer, maxImages,
                                               /*controlledByApp*/true);
    ...

    //ImageReader的消费者
    ctx->setCpuConsumer(consumer);

    //ImageReader的生产者，gbProducer会用来创建Surface
    ctx->setProducer(gbProducer);
    ....
}

//使用gbProducer来创建Surface
static jobject ImageReader_getSurface(JNIEnv* env, jobject thiz)
{
    ALOGV("%s: ", __FUNCTION__);

    IGraphicBufferProducer* gbp = ImageReader_getProducer(env, thiz);
    if (gbp == NULL) {
        jniThrowRuntimeException(env, "CpuConsumer is uninitialized");
        return NULL;
    }

    // Wrap the IGBP in a Java-language Surface.
    return android_view_Surface_createFromIGraphicBufferProducer(env, gbp);
}