QAbstractVideoSurface::present not triggered

[RyuShai]

i want grap frame from webcam to procees so i implement QAbstractVideoSurface
But event camera state change to QCamera::ActiveState, i dont see present fucntion called
implement surface

QList<QVideoFrame::PixelFormat> AndroidFrame::supportedPixelFormats(QAbstractVideoBuffer::HandleType handleType) const
{
    if (handleType == QAbstractVideoBuffer::NoHandle) {
           return QList<QVideoFrame::PixelFormat>()
                   << QVideoFrame::Format_RGB32;
       } else {
           return QList<QVideoFrame::PixelFormat>();
    }
}

bool AndroidFrame::present(const QVideoFrame &currentFrame)
{
    qDebug()<<Q_FUNC_INFO;
    qDebug()<<currentFrame.pixelFormat()<<endl;
    if (currentFrame.isValid()) {
        QVideoFrame cloneFrame(currentFrame);
        cloneFrame.map(QAbstractVideoBuffer::ReadOnly);
        const QImage img(cloneFrame.bits(),
                     cloneFrame.width(),
                     cloneFrame.height(),
                     QVideoFrame::imageFormatFromPixelFormat(cloneFrame.pixelFormat()));
         emit frameChanged(img);
        return true;
    }
    return false;
}

call in main

QCamera *camera;
    BindingFrame2QML *binding = new BindingFrame2QML();
    QList<QCameraInfo> cameras = QCameraInfo::availableCameras();
    foreach (const QCameraInfo &cameraInfo, cameras) {
        qDebug()<<cameraInfo.deviceName()<<endl;
        if (cameraInfo.deviceName() == "/dev/video0")
            camera = new QCamera(cameraInfo);
    }

    AndroidFrame *viewFinder = new AndroidFrame;
    camera->setCaptureMode(QCamera::CaptureMode::CaptureViewfinder);
    camera->setViewfinder(viewFinder);

    QObject::connect(viewFinder,&AndroidFrame::frameChanged,binding,&BindingFrame2QML::onFrameUpdate);
    QObject::connect(camera,&QCamera::stateChanged,[=](QCamera::State state){
        qDebug()<<"state: "<<state;

    });
    camera->start();

BindingFrame2QML is Qimageprovider to sent image from c++ to qml so it does't matter

here log of QCameraState

state: QCamera::ActiveState

[RyuShai]

@RyuShai Problem solve, look like root cause is my code in main.cpp call before

QGuiApplication app(argc, argv);

move line code above to the top of main function make it find