Qt线程调用问题
请帮我。我对线程概念感到震惊。实际上我的问题:我想在组合框中显示城市列表。我从网络服务获取城市列表。我正在使用线程在 Web 服务调用完成后更新组合框值。
在这里我可以调用网络服务。但我无法得到回复。
我正在使用以下代码。
MainWindow.cpp:
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
CGNetwork *cgNetwork = new CGNetwork();
ui->setupUi(this);
renderThread = new RenderThread(cgNetwork);
renderThread->start();
connect(renderThread,SIGNAL(finished()),this,SLOT(initControls()));
}
void MainWindow::initControls()
{
CGMainWindowUtility *pointer = CGMainWindowUtility::instance();
QStringList cityitems;
cityitems <<tr("All");
cityitems.append(pointer->getCityList());
QStringListModel *cityModel = new QStringListModel(cityitems, this);
ui->cityComboBox->setModel(cityModel);
}
RenderThread.cpp:
RenderThread::RenderThread(CGNetwork *cgnetwork)
{
cityUrl = "http://112.138.3.181/City/Cities";
categoryUrl = "http://112.138.3.181/City/Categories";
}
void RenderThread::run()
{
qDebug()<< "THREAD Started";
CGNetwork *cgnetworks = new CGNetwork();
cgnetworks->getCityList(cityUrl);
}
CGNetwork.cpp:
void CGNetwork ::getCityList(const QUrl url)
{
cityGuideNetworkAccessManager = new QNetworkAccessManager(this);
qDebug()<<"connection";
connect(cityGuideNetworkAccessManager, SIGNAL(finished(QNetworkReply*)),
this, SLOT(parseCityList()));
const QNetworkRequest cityRequest(url);
cityReply= cityGuideNetworkAccessManager->get(cityRequest);
connect(cityReply, SIGNAL(error(QNetworkReply::NetworkError)),
this, SLOT(slotError()));
}
void CGNetwork::parseCityList()
{
qDebug()<<"Parsing";
cgParser = new CGJsonParser();
cgParser->CityRead(cityReply);
}
Please help me. I am struck-up with thread concept. Actually my problem : I want to display the cities List in the combobox. I am getting cities list from the webservice. I am using thread for update the combo box value after webserice call finished.
Here I can call the webservice. But I couldn't get the Reply.
I am using the following code.
MainWindow.cpp:
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
CGNetwork *cgNetwork = new CGNetwork();
ui->setupUi(this);
renderThread = new RenderThread(cgNetwork);
renderThread->start();
connect(renderThread,SIGNAL(finished()),this,SLOT(initControls()));
}
void MainWindow::initControls()
{
CGMainWindowUtility *pointer = CGMainWindowUtility::instance();
QStringList cityitems;
cityitems <<tr("All");
cityitems.append(pointer->getCityList());
QStringListModel *cityModel = new QStringListModel(cityitems, this);
ui->cityComboBox->setModel(cityModel);
}
RenderThread.cpp:
RenderThread::RenderThread(CGNetwork *cgnetwork)
{
cityUrl = "http://112.138.3.181/City/Cities";
categoryUrl = "http://112.138.3.181/City/Categories";
}
void RenderThread::run()
{
qDebug()<< "THREAD Started";
CGNetwork *cgnetworks = new CGNetwork();
cgnetworks->getCityList(cityUrl);
}
CGNetwork.cpp:
void CGNetwork ::getCityList(const QUrl url)
{
cityGuideNetworkAccessManager = new QNetworkAccessManager(this);
qDebug()<<"connection";
connect(cityGuideNetworkAccessManager, SIGNAL(finished(QNetworkReply*)),
this, SLOT(parseCityList()));
const QNetworkRequest cityRequest(url);
cityReply= cityGuideNetworkAccessManager->get(cityRequest);
connect(cityReply, SIGNAL(error(QNetworkReply::NetworkError)),
this, SLOT(slotError()));
}
void CGNetwork::parseCityList()
{
qDebug()<<"Parsing";
cgParser = new CGJsonParser();
cgParser->CityRead(cityReply);
}
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由于 QNetworkAccessManager 异步工作,因此不需要单独的线程。您可以直接从主线程调用
getCityList
并且它不会阻塞。我认为您的插槽未被调用,因为您的
QThread::run
在其正在执行的任何工作有机会完成之前返回,因为getCityList
刚刚发起了一个 http 请求无需等待(因为 QNetworkAccessManager::get 不会像我上面所说的那样阻塞)。另外作为旁注,您的插槽没有获得与其相应信号相同的参数,我不记得 Qt 是否支持这一点。
Since
QNetworkAccessManager
works asynchronously, there's no need for a separate thread. You can callgetCityList
directly from your main thread and it won't block.I think your slots weren't called because your
QThread::run
returned before any of the work its been doing had a chance to complete, sincegetCityList
just initiated an http request without waiting for it (becauseQNetworkAccessManager::get
doesn't block like I said above).Also as a side note, your slots aren't getting the same parameters as their corresponding signals, I don't remember if Qt supports this.