从QThread使用QCamera/QCameraInfo

Question

我有一个Camera类，目前只是返回有多少个可用摄像头连接到计算机。在我的PhotoProcessor类(QWidget)中创建了一个Camera对象，然后将其移动到另一个线程，因为我注意到在检查可用的Camera时有一些轻微的挂起：

在photoprocessor.cpp中

void PhotoProcessor::GetAvailableCameras()
{
    //Create new camera to go and fetch number of cameras.
    Camera *camera_connection = new Camera;

    //Create thread and send away.
    QThread *thread = new QThread;
    camera_connection->moveToThread(thread);
    connect(camera_connection, SIGNAL(CameraCountSignal(int)), this, SLOT(CameraCountSlot(int)));
    connect(thread, SIGNAL(started()), camera_connection, SLOT(GetAvailableCameras()));
    connect(camera_connection, SIGNAL(CloseCameraThreadSignal()), thread, SLOT(quit()));
    connect(camera_connection, SIGNAL(CloseCameraThreadSignal()), camera_connection, SLOT(deleteLater()));
    connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));
    thread->start();

    return;
}

camera.h

#ifndef CAMERA_H
#define CAMERA_H

#include <QObject>
#include <QCamera>
#include <QCameraInfo>

class Camera : public QObject
{
    Q_OBJECT

public:
    Camera();

public slots:
    void GetAvailableCameras();

signals:
    void CameraCountSignal(int);
    void CloseCameraThreadSignal();
};

#endif // CAMERA_H

camera.cpp

#include "camera.h"

Camera::Camera()
{

}

void Camera::GetAvailableCameras()
{  
    QList<QCameraInfo> cameras = QCameraInfo::availableCameras();
    emit CameraCountSignal(cameras.size());
    emit CloseCameraThreadSignal();
    return;
}

当从photoprocessor.cpp运行QCameraInfo::availableCameras()时，它告诉我连接了一个摄像头，这是正确的，但是无论我做什么，线程摄像头对象都无法检测到摄像头，即摄像头的大小为零。

这是怎么回事？

Answer 1

一年后，我决定再次讨论这个问题。

我想在我的实际代码中，我创建了一个QCamera对象，当线程被删除时，我错误地删除了，线程结束后，我再也找不到使用QCameraInfo::availableCameras()的相机了。

显式设置新QCamera对象的父级为我修复了此问题，即

QCamera *camera = new QCamera(QCameraInfo);
camera->setParent(this);