Unable to connect using QML Remote Object with Error: "connectionToSource is null"

Question

我正在尝试使用 Qt 远程对象来创建客户端服务器应用程序。但是遇到了一个问题，说“connectionToSource is null”。如何设置源连接？

我正在使用 .rep 文件创建服务器。我使用的代码如下：

数据模型

// Rep File (DataModel.rep)
class DataModel {
    PROP(double data)
}

服务器代码

// DataBroadcaster class (DataBroadcaster.h)
// DataBroadcaster class inherits DataModelSimpleSource.h (generated from .rep file)    
    #include "rep_DataModel_Source.h"
    class DataBroadcaster : public DataModelSimpleSource
    {
        Q_OBJECT
        public:
            DataBroadcaster(QObject *parent = nullptr);
            ~DataBroadcaster();
        void Initialize();
            private:
            int QScopedPointer<QRemoteObjectHost> remoteHost;
    }

// DataBroadcaster.cpp

DataBroadcaster::DataBroadcaster(QObject *parent): DataModelSimpleSource(parent){}
DataBroadcaster::~DataBroadcaster(){}
void DataBroadcaster::Initialize()
{
    remoteHost.reset(new QRemoteObjectHost(QUrl(QStringLiteral("local:mydata"))));
    remoteHost->enableRemoting(this, "DataModel");
}

//服务器代码主函数

#include <QCoreApplication>
#include "DataBroadcaster.h"
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    DataBroadcaster server;
    server.Initialize();    
    double count = 0.0;
    while(true)
    {
        server.pushData(count + 0.1);
    }   
    return a.exec();
}

客户代码

// DataModelDataReplica is generated from .rep file used to generate source
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>

#include "rep_DataModel_replica.h"

int main(int argc, char *argv[])
{
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
#endif

    QGuiApplication app(argc, argv);
    QQmlApplicationEngine engine;
    // registered as qml type in main
    qmlRegisterType<DataModelReplica>("CustomData", 1, 0, "MyData");
    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     &app, [url](QObject *obj, const QUrl &objUrl) {
        if (!obj && url == objUrl)
            QCoreApplication::exit(-1);
    }, Qt::QueuedConnection);
    engine.load(url);
    return app.exec();
}

QML 代码

// DisplayPage.qml Added to QML file    
import CustomData 1.0    
MyData {
    id: dataClient
    node: Node {
        registerUrl: "local:mydata"
    }
    Button {
        id: btn
        text: "Server Data" 
        onClicked: {
            // displaying some data from source
            btn.text = dataClient.data
        }
    }
}

执行：

Server code is running
Client code is running but when trying to get data I get following error message in debugger
**"qt.remoteobjects: connectionToSource is null"**

我不知道我错过了什么。如果有人知道如何解决或在哪里寻找，请提出建议。

Answer 1

我找到了问题所在。在 Server Code main 函数中，使用了 while 循环，它永远不会退出，因此“exec()”函数从未被调用，Qt 事件循环也从未启动，因此 Qt Remote 对象没有共享数据。所以我使用 Signal and Slot 机制更改了以下代码以创建非阻塞函数。以下是我所做的代码更改。

//服务器代码主要功能

#include <QCoreApplication>
#include "DataBroadcaster.h"
#include "ServerController.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    DataBroadcaster server;
    server.Initialize(); 
    ServerController controller(&server);
    return a.exec();
}

// 服务器控制器

#include <QTimer>
#include "DataBroadcaster.h"

class ServerController : public QObject
{
Q_OBJECT
public:
    explicit ServerController(QObject *parent = nullptr, DataBroadcast *server = nullptr);
    ~ServerController();

public Q_SLOTS:
    void SendData();

private:
    QTimer timer;
    double count = 0.0; 
    DataBroadcast *m_server = nullptr;
}

ServerController::ServerController(QObject *parent, DataBroadcast *server): QObject(parent), m_server(server)
{
    connect(&timer, SIGNAL(timeout()), this, SLOT(SendData()));
    timer.start();
}

ServerController::~ServerController()
{
    timer.stop();
}

ServerController::SendData()
{
    count += 0.1;
    if(m_server != nullptr)
    {
         m_server->pushData(count);
    }
}

Unable to connect using QML Remote Object with Error: "connectionToSource is null"

Unable to connect using QML Remote Object with Error: "connectionToSource is null"

c++

qt

qml

qtremoteobjects