I've "Core" object that handles QMainWindow.
Core.h code
class Core : public QObject
{
Q_OBJECT
public:
explicit Core(QObject *parent = 0);
~Core();
void appInit();
int getAuth();
public slots:
void appExit();
private slots:
void appMenuTriggered(QAction *action);
private:
void preInit();
MainWindow *mwnd;
};
Core.cpp code
Core::Core(QObject *parent) : QObject(parent)
{
qDebug() << "Core::Constructor called";
preInit();
}
Core::~Core()
{
delete mwnd;
qDebug() << "Core::Destructor called";
}
int Core::getAuth()
{
LoginDialog *login = new LoginDialog();
int r = login->exec();
delete login;
return r;
}
void Core::appExit() // connected to qapplication aboutToQuit
{
qDebug() << "Core::appExit called";
}
void Core::preInit() // called after getAuth im main.cpp
{
qDebug() << "Core::preInit called";
}
void Core::appMenuTriggered( QAction *action )
{
qDebug() << "action triggered";
}
void Core::appInit()
{
mwnd = new MainWindow();
mwnd->show();
qDebug() << "Core::appInit called";
}
I'm trying to connect mainwindow menubar signal to core slot like this:
connect(mwnd->menuBar(), SIGNAL(triggered()), this, SLOT(appMenuTriggered()));
But it doesn't work. Im new to c++ and Qt. How to connect this?
Or maybe there is better way to handle mainwindow actions to other programm parts.
UPD
Problem solved. Forget to include QMenuBar
You have to give the full function spec in the SIGNAL and SLOT parameters (but without the argument names). Like this:
connect(mwnd->menuBar(),
SIGNAL(triggered(QAction*)),
this,
SLOT(appMenuTriggered(QAction*)));
If you debug such code in Qt Creator, the connect function will write diagnostic error messages to the Application Output pane when it doesn't find a signal or a slot. I suggest that you find these error messages before you fix your problem, so that you know where to look in future. It's very easy to get signals and slots wrong!
Related
I try to read out the output of a command executed in QProcess. I don't get the connection working between QProcess's finished signal and a finished handler.
I tried several different ways of connecting to QProcess finished signal but no luck so far. I know that the process executes because it prints the output in the GUI's console and that the process finishes because it passes the waitForFinished method from sequential API.
Why does my code not hit onFinish or onFinishNoPams?
header:
class Test : public QObject
{
Q_OBJECT
public:
Test(QObject *parent = 0);
Q_INVOKABLE void read();
public slots:
void onFinish(int exitCode , QProcess::ExitStatus exitStatus);
void onFinishNoPams();
private:
QProcess *m_process;
};
cpp:
Test::Test(QObject *parent)
: QObject(parent)
{}
void Test::read(){
m_process=new QProcess(this);
connect(m_process, SIGNAL(finished(int,QProcess::ExitStatus)), this, SLOT(onFinishNoPams()));
connect(m_process, SIGNAL(finished(int,QProcess::ExitStatus)), this, SLOT(onFinish(int,QProcess::ExitStatus)));
connect(m_process, QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished),
[=](int exitCode, QProcess::ExitStatus exitStatus){
qDebug() << "not reached";
});
connect(m_process, QOverload<int, QProcess::ExitStatus>::of(&QProcess::finished), this,&Test::onFinish);
QString program = "lsusb";
QStringList arguments;
m_process->execute(program,arguments);
m_process->waitForFinished();
qDebug() << "reached";
return;
}
void Test::onFinish(int exitCode , QProcess::ExitStatus exitStatus){
qDebug() << "not reached";
}
void Test::onFinishNoPams(){
qDebug() << "not reached";
QByteArray out=m_process->readAllStandardOutput();
}
qml:
import test 1.0
Window {
Test{
id:test
Component.onCompleted: test.read()
}
}
QProcess::execute() is a static method that starts the external process and waits for its completion in a blocking way. It has nothing to do with your m_process variable. What you want to use is QProcess::start().
I use the old connection syntax until now. Today I want to change my project to new connection syntax like this:
#include <QDebug>
class Telefon : public QObject {
Q_OBJECT
public:
void letRing() {
qDebug() << "letRing";
emit ring();
}
signals:
void ring();
public slots:
void onRing() {
qDebug() << "onRing";
}
};
class Cable : public QObject {
Q_OBJECT
signals:
void ring();
};
int main(int argc, char *argv[])
{
Telefon *fon1 = new Telefon();
Telefon *fon2 = new Telefon();
Cable *cable = new Cable();
// old connection way
// connect(fon1, SIGNAL(ring()), cable, SIGNAL(ring()));
// connect(cable, SIGNAL(ring()), fon2, SLOT(onRing()));
// new connection way
QObject::connect(fon1, &Telefon::ring, cable, &Cable::ring); // <-- This is the problem
QObject::connect(cable, &Cable::ring, fon2, &Telefon::onRing);
fon1->letRing();
return 0;
}
The compiling went well with no errors. But the telefon never rings :(
Output should be:
letRing
onRing
But it is:
letRing
I Dig into the Qt code and found that SIGNAL-SLOT connections where valid but SIGNAL-SIGNAL connections don't work this way. Beside it generate no error while compiling. Is there a way to connect SIGNALs the new way/syntax?
I want to create two-way communicate beetwen my Qt Apps. I want to use QProcess to do this. I'm calling sucesfully child app from root app and sending test data without any erro, but I can't recive any data in child app. I'll be gratefull for any help. I'm using Qt 4.7.1. Below my test code:
Root app:
InterProcess::InterProcess(QObject *parent) : QProcess(parent)
{
process = new QProcess(this);
process->start(myChildApp);
process->waitForStarted();
process->setCurrentWriteChannel(QProcess::StandardOutput);
process->write("Test");
connect( process, SIGNAL(error(QProcess::ProcessError)), this, SLOT(error(QProcess::ProcessError)) );
connect( process, SIGNAL(readyReadStandardError()), this, SLOT(readyReadStandardError()) );
connect( process, SIGNAL(readyReadStandardOutput()), this, SLOT(readyReadStandardOutput()) );
QByteArray InterProcess::read()
{
QByteArray readBuffer = process->readAllStandardOutput();
return readBuffer;
}
void InterProcess::error( QProcess::ProcessError error )
{
qDebug() << "Error!";
qDebug() << error;
}
void InterProcess::readyReadStandardError()
{
qDebug() << "Ready to read error.";
qDebug() << process->readAllStandardError();
}
void InterProcess::readyReadStandardOutput()
{
qDebug() << "The output:";
QByteArray readBuffer = process->readAllStandardOutput();
qDebug() << readBuffer;
}
Child app:
InterProcess::InterProcess(QObject *parent) : QProcess(parent)
{
process = new QProcess();
process->setCurrentReadChannel(QProcess::StandardOutput);
connect( process, SIGNAL(readyRead()), this, SLOT(readyReadStandardOutput()));
connect( process, SIGNAL(error(QProcess::ProcessError)), this, SLOT(error(QProcess::ProcessError)) );
connect( process, SIGNAL(readyReadStandardError()), this, SLOT(readyReadStandardError()) );
connect( process, SIGNAL(readyReadStandardOutput()), this, SLOT(readyReadStandardOutput()) );
process->waitForReadyRead(5000);
}
void InterProcess::readyReadStandardError()
{
qDebug() << "Ready to read error.";
qDebug() << process->readAllStandardError();
setText("REady error");
}
void InterProcess::readyReadStandardOutput()
{
setMessage("2");
qDebug() << "The output:";
QByteArray readBuffer = process->readAllStandardOutput();
qDebug() << readBuffer;
}
void InterProcess::error( QProcess::ProcessError error )
{
qDebug() << "Error!";
qDebug() << error;
setText(QString(error));
}
It's very hard to explain in one answer all mistakes, so just look at code and ask if you still got problems.
Here is example of using QProcess as IPC.
This is your main process, that creates additional process and connects to its signals
MyApplicaiton.h
#ifndef MYAPPLICATION_H
#define MYAPPLICATION_H
#include <QApplication>
class InterProcess;
class MyApplication : public QApplication {
Q_OBJECT
public:
MyApplication(int &argc, char **argv);
signals:
void mainApplicationSignal();
private slots:
void onInterProcessSignal();
private:
InterProcess *mProcess;
};
#endif // MYAPPLICATION_H
MyApplicaiton.cpp
#include "MyApplication.h"
#include "InterProcess.h"
MyApplication::MyApplication(int &argc, char **argv) : QApplication(argc, argv) {
mProcess = new InterProcess(this);
connect(mProcess, SIGNAL(interProcessSignal()),
this, SLOT(onInterProcessSignal()));
mProcess->start();
}
void MyApplication::onInterProcessSignal() {}
This is example implementation of your interProcess class:
InterProcess.h
class InterProcess : public QProcess {
Q_OBJECT
public:
explicit InterProcess(QObject *parent = nullptr);
signals:
void interProcessSignal();
private slots:
void onMainApplicationSignal();
};
InterProcess.cpp
#include "InterProcess.h"
#include "MyApplication.h"
InterProcess::InterProcess(QObject *parent) : QProcess(parent) {
if(parent) {
auto myApp = qobject_cast<MyApplication *>(parent);
if(myApp) {
connect(myApp, SIGNAL(mainApplicationSignal()),
this, SLOT(onMainApplicationSignal()));
}
}
}
void InterProcess::onMainApplicationSignal() {}
Locally, using UDP is very convenient and efficient
void Server::initSocket() {
udpSocket = new QUdpSocket(this);
udpSocket->bind(QHostAddress::LocalHost, 7755);
connect(udpSocket, SIGNAL(readyRead()), this, SLOT(readPendingDatagrams()));}
void Server::readPendingDatagrams(){
while (udpSocket->hasPendingDatagrams()) {
QByteArray datagram;
datagram.resize(udpSocket->pendingDatagramSize());
QHostAddress sender;
quint16 senderPort;
udpSocket->readDatagram(datagram.data(), datagram.size(),
&sender, &senderPort);
processTheDatagram(datagram);
}}
I'm developing a multithreaded application, I need to instantiate n devices by modbus.
So I created a controller (ServiceSM) that instantiates N threads (ServiceSlots).
The devices are varied so I had to create "drivers" for each type of device, one of the drivers uses the QModbusClient class, so I created a controller to manage the device type.
schema
To test the operation of the state machine and connection to the device, I made an example code to run in a graphical interface.
I deleted some snippets of code that do not matter to make it easier to understand
In the MD4040driver class
When my code runs this section, the following messages appear.
If I instantiate the DeviceDriver class in the graphical interface, it works perfectly, the problem occurs when I instantiate it inside a thread.
when calls
modbusDevice->connectDevice()
MD4040drive::sm_conn() - try connect - this my message
Error:
QObject::connect: Cannot queue arguments of type
'QModbusDevice::State' (Make sure 'QModbusDevice::State' is registered
using qRegisterMetaType().)
QObject: Cannot create children for a parent that is in a different
thread. (Parent is QTcpSocket(0x24a6ce8), parent's thread is
ServiceSlots(0xea66488), current thread is QThread(0x2418a78)
QObject: Cannot create children for a parent that is in a different
thread. (Parent is QTcpSocket(0x24a6ce8), parent's thread is
ServiceSlots(0xea66488), current thread is QThread(0x2418a78)
void MD4040drive::sm_conn()
{
if (modbusDevice->state() != QModbusDevice::ConnectedState) {
modbusDevice->setConnectionParameter(QModbusDevice::NetworkPortParameter, this->cfg.modbus.porta );
modbusDevice->setConnectionParameter(QModbusDevice::NetworkAddressParameter, this->cfg.modbus.ip);
modbusDevice->setTimeout( this->cfg.modbus.timeout );
modbusDevice->setNumberOfRetries(this->cfg.modbus.retries);
qDebug() << "MD4040drive::sm_conn() - try connect";
if (!modbusDevice->connectDevice()) {
qDebug() << "Erro: " << modbusDevice->errorString();
} else {
qDebug() << "Aguardando conexão...";
}
}
else{
//already connected...
this->getDados_NO_TH();
}
}
rest my code(parts)
devicedriverviewgui.h
devicedriverviewgui.cpp
class DeviceDriverViewGUI : public QDialog
{
Q_OBJECT
public:
explicit DeviceDriverViewGUI(QWidget *parent = 0);
~DeviceDriverViewGUI();
private slots:
void on_pbTry_clicked();
private:
Ui::DeviceDriverViewGUI *ui;
ServiceSlots *serviceSlot;
};
void DeviceDriverViewGUI::on_pbTry_clicked()
{
Equip equip_try = Equip();
serviceSlot = new ServiceSlots();
serviceSlot->setEquipamento(equip_try);
serviceSlot->start();
}
serviceslots.h
serviceslots.cpp
class ServiceSlots : public QThread
{
Q_OBJECT
public:
ServiceSlots();
void run();
private:
QTimer *timer;
DeviceDriver *device;
private slots:
void sm_getData();
void device_response(bool boEnd);
};
void ServiceSlots::run()
{
int e;
eventLoop = new QEventLoop();
timer = new QTimer();
connect(timer, SIGNAL(timeout()),this, SLOT(sm_controler()));
timer->start(TICK_SM_SLOT);
this->device = new DeviceDriver();
e = eventLoop->exec();
qDebug() << "Exit loop"<< e;
}
void ServiceSlots::sm_controler()
{
if(this->idleState){;}
else{
this->sm_getData();
this->idleState = true;
}
}
void ServiceSlots::sm_getData()
{
connect(device,SIGNAL(end(bool)),this,SLOT(device_response(bool)));
device->requestDeviceDriver(&this->equipamento,&this->next_date);
}
devicedriver.h
devicedriver.cpp
class DeviceDriver : public QObject
{
Q_OBJECT
public:
DeviceDriver();
void requestDeviceDriver(Equip *equip,QDateTime *date);
private:
//Drivers de dispositivos..
MD4040drive *md4040;
private slots:
//Request data to driver...
void request();
signals:
void end(bool boEnd);
};
void DeviceDriver::request()
{
connect(md4040,SIGNAL(end(bool)),this,SLOT(md4040_end(bool)));
this->md4040->requestMD4040drive(&this->equip,&this->date);
}
DeviceDriver::DeviceDriver(){
----
md4040 = new MD4040drive();
---
}
void DeviceDriver::requestDeviceDriver(Equip *equip, QDateTime *date){
this->equip = *equip;
this->date = *date;
this->request();
}
md4040drive.h
md4040drive.cpp
class MD4040drive : public QObject // QObject//public QObject QRunnable QThread
{
Q_OBJECT
public:
explicit MD4040drive(QObject *parent = 0);
~MD4040drive();
void requestMD4040drive(Equip *equip,QDateTime *date);
private:
void run();
QModbusClient *modbusDevice;
private slots:
void m_conn();
signals:
void end(bool boRun);
};
MD4040drive::MD4040drive(QObject *parent): QObject(parent)
{
modbusDevice = new QModbusTcpClient();
connect(modbusDevice, &QModbusClient::stateChanged,this, &MD4040drive::onStateChanged);
}
void MD4040drive::requestMD4040drive(Equip *equip, QDateTime *date)
{
this->equip = *equip;
this->date = *date;
this->run();
}
void MD4040drive::run()
{
this->sm_conn();
}
void MD4040drive::sm_conn()
{
if (modbusDevice->state() != QModbusDevice::ConnectedState) {
modbusDevice->setConnectionParameter(QModbusDevice::NetworkPortParameter, this->cfg.modbus.porta );
modbusDevice->setConnectionParameter(QModbusDevice::NetworkAddressParameter, this->cfg.modbus.ip);
modbusDevice->setTimeout( this->cfg.modbus.timeout );
modbusDevice->setNumberOfRetries(this->cfg.modbus.retries);
qDebug() << "MD4040drive::sm_conn() - try connect";
if (!modbusDevice->connectDevice()) {
qDebug() << "Erro: " << modbusDevice->errorString();
} else {
qDebug() << "Aguardando conexão...";
}
}
else{
//already connected...
this->getDados_NO_TH();
}
}
There are a few problems:
You need to call qRegisterMetaType<QModbusDevice::State>() in main().
You need to maintain parent-child relationships between all objects that are potentially moved to other threads as a group.
The ServiceSlots and DeviceDriver classes seem to be unnecessary.
The ubiquitous this-> is non-idiomatic C++. Don't write this-> unless you need to disambiguate a member from a local variable.
Prefer to hold objects by value if they have the same lifetime as the parent object. Let the compiler generate memory management code for you!
Leverage C++11.
Fist of all, let's have a helper SafeThread class that provides us with a thread that is safely destructible at any time:
class SafeThread : public QThread {
Q_OBJECT
using QThread::run;
public:
using QThread::QThread;
~SafeThread() { quit(); wait(); }
};
The DeviceDriverViewGUI class can hold the drive and its thread by value:
class DeviceDriverViewGUI : public QDialog
{
Q_OBJECT
public:
explicit DeviceDriverViewGUI(QWidget *parent = nullptr);
private:
Ui::DeviceDriverViewGUI ui;
MD4040drive drive;
SafeThread driveThread{this};
Equip equipamento;
QDateTime nextDate;
Q_SLOT void on_pbTry_clicked();
};
Then, the pushbutton can be connected directly to the drive's thread context, and run the requestMD4040drive in the proper thread:
DeviceDriverViewGUI::DeviceDriverViewGUI(QWidget *parent) : QDialog(parent)
{
ui.setupUi(this);
// vvvvvv -- gives the thread context
connect(ui.pbTry, &QPushButton::clicked, &drive, [this]{
Q_ASSERT(QThread::currentThread() == drive.thread()); // ensured by the thread context
drive.requestMD4040drive(&equipamento, nextDate);
});
connect(&drive, &MD4040drive::end, this, [this](bool end){
//...
});
drive.moveToThread(&driveThread);
driveThread.start();
}
When done this way, you don't need any extraneous helper objects nor timers to queue requests. Qt handles all of it.
When passing Qt value classes to functions, pass them by const reference, not by pointer. The MD4040drive should look roughly as follows:
class MD4040drive : public QObject
{
Q_OBJECT
public:
explicit MD4040drive(QObject *parent = nullptr);
void requestMD4040drive(Equip *equip, const QDateTime &date);
Q_SIGNAL void end(bool boRun);
private:
Equip *equip = nullptr;
QDateTime date;
QModbusTcpClient modbusDevice{this};
Cfg cfg;
Q_SLOT void onStateChanged();
Q_SLOT void m_conn();
void sm_conn();
void getDados_NO_TH() {}
};
The implementation:
MD4040drive::MD4040drive(QObject *parent): QObject(parent)
{
connect(&modbusDevice, &QModbusClient::stateChanged,this, &MD4040drive::onStateChanged);
}
void MD4040drive::requestMD4040drive(Equip *equip, const QDateTime &date)
{
this->equip = equip;
this->date = date;
sm_conn();
}
void MD4040drive::sm_conn()
{
if (modbusDevice.state() != QModbusDevice::ConnectedState) {
modbusDevice.setConnectionParameter(QModbusDevice::NetworkPortParameter, cfg.modbus.porta );
modbusDevice.setConnectionParameter(QModbusDevice::NetworkAddressParameter, cfg.modbus.ip);
modbusDevice.setTimeout( this->cfg.modbus.timeout );
modbusDevice.setNumberOfRetries(this->cfg.modbus.retries);
qDebug() << "MD4040drive::sm_conn() - try connect";
if (!modbusDevice.connectDevice()) {
qDebug() << "Erro: " << modbusDevice.errorString();
} else {
qDebug() << "Aguardando conexão...";
}
}
else{
//already connected...
getDados_NO_TH();
}
}
The configuration class might look as follows - notice that the compiler will generate the necessary constructors and destructors for you:
struct Cfg {
struct Modbus {
int porta = 0;
QString ip = QStringLiteral("127.0.0.1");
int timeout = 1000;
int retries = 2;
} modbus;
};
Make sure 'QModbusDevice::State' is registered using qRegisterMetaType()
Means you need to call qRegisterMetaType<QModbusDevice::State>(); before connecting signal/slot that would pass this type of parameter between threads.
And/or add Q_DECLARE_METATYPE(QModbusDevice::State) macro at global scope (never understood clearly which one is actually needed, putting both works for sure...).
See this post for more details: Emitting signals with custom types does not work
This is my class declaration:
class Browser : public QWidget {
Q_OBJECT
public:
Browser(QWidget *parent = 0);
QStringList loadSettings(QString settings_file);
private slots:
void toggleFullscreen();
private:
void createActions();
QAction *aToggleFullscreen;
};
And relevand definitions:
void Browser::toggleFullscreen() {
out << "fullscreen!" << endl;
}
void Browser::createActions() {
aToggleFullscreen = new QAction(this);
aToggleFullscreen->setShortcut(tr("F11"));
connect(aToggleFullscreen, SIGNAL(triggered()), this, SLOT(toggleFullscreen()));
}
I'm calling createActions() from Browser::Browser.
I have no runtime warning that slot doesn't exists, etc. But still nothing is triggered if I hit F11.
I tried also:
aToggleFullscreen->setShortcut(QString("F11"));
What is it wrong with my code?
You forgot to actually add your action to the Browser, so it never gets triggered. This should work:
void Browser::createActions() {
aToggleFullscreen = new QAction(this);
aToggleFullscreen->setShortcut(tr("F11"));
connect(aToggleFullscreen, SIGNAL(triggered()), this, SLOT(toggleFullscreen()));
addAction(aToggleFullscreen);
}