I can't figure out what's going wrong here.
I want to pass a value from a class to another.
Here's the code:
mainwindow.h
public slots:
void printNumbers(int);
mainwindow.cpp
void MainWindow::printNumbers(int a)
{
qDebug() << a;
}
myudp.h
signals:
inline void sendBuff(int);
myudp.cpp
[***]
MainWindow *widget = new MainWindow();
connect(socket, SIGNAL(readyRead()), this, SLOT(readyRead()));
const bool connected = connect(this , SIGNAL(sendBuff(int)), widget ,SLOT(printNumbers(int)));
qDebug() << "Connection established?" << connected;
[***]
void MyUDP::readyRead()
{
// when data comes in
emit sendBuff(13);
[***]
}
inline void MyUDP::sendBuff(int a)
{
qDebug() << "sending " << a ;
}
Main.cpp
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QMainWindow window;
MainWindow *widget = new MainWindow();
window.setCentralWidget(widget);
window.resize(900, 600);
window.show();
MyUDP *client = new MyUDP();
return a.exec();
}
I used "inline" because of an error: duplicate MyUDP::sendBuff(int a).
I don't know if it can be an issue.
when I execute the "emit sendBuff(12)" I only receive "sending 12", I didn't catch the printNumbers()'s output even if the variable "connected" is true.
remove the inline declaration of the slot, and if your class needs an internal use for sendBuff then declare a new method for that...
signals:
void sendBuffSignal(int);
and in the cpp
void MyUDP::sendBuff(int a)
{
qDebug() << "sending " << a ;
}
Related
Necessary informations:
QList<QTcpSocket*> list;
QTcpServer* server;
QTcpSocket* socket;
In Qt I have built a TCP-Server(QTcpServer)! I have a QList with all my connected clients and I want to read the incomming data for each client personally. So if the QTcpServer gets a new connection, I handel it like this:
void Server::newConnection()
{
qDebug() << "New Connection";
list.append(server->nextPendingConnection());
connect(list.last(),SIGNAL(readyRead()),this,SLOT(readyRead()));
}
How can I get the correct client (out of my QList), which send the SIGNAL readyRead(), in my SLOT readyRead()?
void Server::readyRead(){
//??
}
Any help is welcomed!
Have you tried QObject::sender()? It should return the instance of the QObject which actually sent the signal. Hope that will help.
The solution:
void Server::readyRead(){
QByteArray buffer;
QTcpSocket* readSocket = qobject_cast<QTcpSocket*>(sender());
buffer = readSocket->readAll();
QString mytext = QString::fromStdString(buffer);
qDebug() << mytext;
}
This could be solved by the QSignalMapper. Here is the (not completelly tested) code:
---------------------- main.cpp ------------------
#include "rootwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
RootWindow w;
w.show();
return a.exec();
}
---------------------- rootwindow.h ------------------------
#ifndef ROOTWINDOW_H
#define ROOTWINDOW_H
#include <QMainWindow>
#include <QtDebug>
#include <QLocalServer>
#include <QLocalSocket>
#include <QSignalMapper>
#include <QList>
class RootWindow : public QMainWindow
{
Q_OBJECT
private:
QLocalServer *server;
QLocalSocket *socket;
QList<QLocalSocket*> *list;
QSignalMapper *mapper;
public:
RootWindow(QWidget *parent = 0);
~RootWindow();
private slots:
void slotNewConnection();
void slotReadyRead(int index);
};
#endif // ROOTWINDOW_H
------------------------ rootwindow.cpp -------------------------
#include "rootwindow.h"
RootWindow::RootWindow(QWidget *parent): QMainWindow(parent)
{
server = new QLocalServer;
list = new QList<QLocalSocket*>;
mapper = new QSignalMapper(this);
connect(server, SIGNAL(newConnection()), this, SLOT(slotNewConnection()));
connect(mapper, SIGNAL(mapped(int)), this, SLOT(slotReadyRead(int)));
server->listen("TestServer");
}
RootWindow::~RootWindow()
{
delete list;
}
void RootWindow::slotNewConnection()
{
qWarning() << "newConnection";
list->append(server->nextPendingConnection());
//here you map each client to its number in the list
mapper->setMapping(list->last(), list->length()-1);
//here we say, that when ever a client from the QList sends readyRead() the mapper should be used
//with the property (list->length()-1) defined in the line above
connect(list->last(), SIGNAL(readyRead()), mapper, SLOT(map()));
}
void RootWindow::slotReadyRead(int index)
{
qWarning() << "Client " << index << " has written: " << list->at(index)->readAll();
}
It's basically your code, I've only added the QSignalMapper and some comments at the relevant lines.
I have been trying to get this simple example using threads activated by pushbuttons to work. It is based off of the solution in the question below:
How to implement frequent start/stop of a thread (QThread)
The main differences between the example solution above and my code below are:
I used a QWidget instead of MainWindow
I changed the name of signals for clarity
My code contains debugging information
I experimented with eliminating the signals created by worker as the didn't appear to do anything
It appears that the start/stop signals are not triggering their corresponding slots, but I am not experienced enough to troubleshoot why.
Additionally, I am unsure of the purpose of the signal:
SignalToObj_mainThreadGUI()
Is that just something that could be used and is not?
I have been trying to get this code to work for some time, so any help would be greatly appreciated.
main.cpp
#include "threadtest.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
ThreadTest w;
w.show();
return a.exec();
}
threadtest.h
#include <QWidget>
#include <QThread>
#include "worker.h"
namespace Ui
{
class ThreadTest;
}
class ThreadTest : public QWidget
{
Q_OBJECT
public:
explicit ThreadTest(QWidget *parent = 0);
~ThreadTest();
signals:
void startWorkSignal();
void stopWorkSignal();
private slots:
void on_startButton_clicked();
void on_stopButton_clicked();
private:
Ui::ThreadTest *ui;
worker *myWorker;
QThread *WorkerThread;
};
threadtest.cpp
#include "threadtest.h"
#include "ui_threadtest.h"
ThreadTest::ThreadTest(QWidget *parent) :
QWidget(parent),
ui(new Ui::ThreadTest)
{
ui->setupUi(this);
myWorker = new worker;
WorkerThread = new QThread;
myWorker->moveToThread(WorkerThread);
connect(this,
SIGNAL(startWorkSignal()),
myWorker,
SLOT(StartWork())
);
connect(this,
SIGNAL(stopWorkSignal()),
myWorker,
SLOT(StopWork())
);
//Debug
this->dumpObjectInfo();
myWorker->dumpObjectInfo();
}
ThreadTest::~ThreadTest()
{
delete ui;
}
void ThreadTest::on_startButton_clicked()
{
qDebug() << "startwork signal emmitted";
emit startWorkSignal();
}
void ThreadTest::on_stopButton_clicked()
{
qDebug() << "stopwork signal emmitted";
emit stopWorkSignal();
}
worker.h
#include <QObject>
#include <QDebug>
class worker : public QObject {
Q_OBJECT
public:
explicit worker(QObject *parent = 0);
~worker();
signals:
void SignalToObj_mainThreadGUI();
//void running();
//void stopped();
public slots:
void StopWork();
void StartWork();
private slots:
void do_Work();
private:
volatile bool running, stopped;
};
worker.cpp
#include "worker.h"
worker::worker(QObject *parent) : QObject(parent), stopped(false),
running(false)
{
qDebug() << "running: " << running;
qDebug() << "stopped: " << stopped;
}
worker::~worker() {}
void worker::do_Work()
{
qDebug() << "inside do Work";
emit SignalToObj_mainThreadGUI();
if (!running || stopped) return;
// actual work here
/*
for (int i = 0; i < 100; i++)
{
qDebug() << "count: " + i;
}
*/
QMetaObject::invokeMethod(this, "do_Work", Qt::QueuedConnection);
}
void worker::StopWork()
{
qDebug() << "inside StopWork";
stopped = true;
running = false;
//emit stopped();
}
void worker::StartWork()
{
qDebug() << "inside StartWork";
stopped = false;
running = true;
//emit running();
do_Work();
}
You should write
WorkerThread->start();
Or you can use the thread of the ThreadTest object instead the WorkerThread (in this case the WorkerThread is needless):
myWorker->moveToThread(thread()); // this->thread
The slots are not triggered, because you have moved myWork to the thread WorkerThread, but didnot run an event loop in that thread. In threadtest.cpp, add
WorkerThread .start();
after
myWorker = new worker;
WorkerThread = new QThread;
myWorker->moveToThread(WorkerThread);
I am trying to implement a simple state machine within a console application. The signals that are supposed to trigger the state transitions are being emitted, however, the state machine is not reacting to those signals.
This state machine works perfectly when running within a QApplication (i.e. a GUI application), however I am wanting to develop a console application. I suspect there is an issue in the way I have implemented the event loop, as the QStateMachine is not emitting the started() signal.
What is the correct way to execute the application in order for the state machine to function correctly?
main.cpp:
#include <QCoreApplication>
#include "test.h"
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
Test test;
QMetaObject::invokeMethod( &test, "Run", Qt::QueuedConnection );
return a.exec();
}
test.h:
#ifndef TEST_H
#define TEST_H
#include <QObject>
#include <QStateMachine>
class Test : public QObject
{
Q_OBJECT
public:
explicit Test(QObject *parent = 0) : QObject(parent) {}
public slots:
void Run();
signals:
void stateChanged();
void debugSignal();
private:
void buildStateMachine();
QStateMachine machine;
private slots:
void runS1();
void runS2();
void runS3();
void debugSlot();
};
#endif // TEST_H
test.cpp:
#include "test.h"
#include <QDebug>
void Test::Run()
{
buildStateMachine();
QTextStream qin(stdin);
while (true)
{
QString line = qin.readLine();
qDebug() << "line: " << line;
if (line == "A")
{
qDebug() << "emit stateChanged signal";
emit stateChanged();
}
else if (line == "B")
{
qDebug() << "emit debugSignal";
emit debugSignal();
}
}
}
void Test::buildStateMachine()
{
connect(&machine, SIGNAL(started()), this, SLOT(debugSlot())); // doesn't seem to get triggered... (why is machine not starting?)
connect(this, SIGNAL(debugSignal()), this, SLOT(debugSlot())); // works as expected
QState *s1 = new QState(&machine);
QState *s2 = new QState(&machine);
QState *s3 = new QState(&machine);
s1->addTransition(this, SIGNAL(stateChanged()), s2);
s2->addTransition(this, SIGNAL(stateChanged()), s3);
s3->addTransition(this, SIGNAL(stateChanged()), s1);
connect(s1, SIGNAL(entered()), this, SLOT(runS1())); // these are never triggered
connect(s2, SIGNAL(entered()), this, SLOT(runS2()));
connect(s3, SIGNAL(entered()), this, SLOT(runS3()));
s1->assignProperty(&machine, "state", 1);
s2->assignProperty(&machine, "state", 2);
s3->assignProperty(&machine, "state", 3);
machine.setInitialState(s1);
machine.start();
}
void Test::runS1()
{
qDebug() << "entered state S1";
}
void Test::runS2()
{
qDebug() << "entered state S2";
}
void Test::runS3()
{
qDebug() << "entered state S3";
}
void Test::debugSlot()
{
qDebug() << "slot was triggered!";
}
Solved my problem. The issue was caused by the infinite while loop. The slot can only be called once the Run function ends, which obviously never occurs.
Here is a working solution. The change to the Qt 5 style signals and slots syntax is optional. If main.cpp is kept as-is from the version shown in the question above, the application will not quit correctly.
main.cpp:
#include <QCoreApplication>
#include <QTimer>
#include "test.h"
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
Test test;
QObject::connect(&test, &Test::finished, &a, &QCoreApplication::quit, Qt::QueuedConnection);
QTimer::singleShot(0, &test, &Test::Run);
return a.exec();
}
test.h:
#ifndef TEST_H
#define TEST_H
#include <QObject>
#include <QStateMachine>
class Test : public QObject
{
Q_OBJECT
public:
explicit Test(QObject *parent = 0);
signals:
void next_state();
void finished();
private:
void buildStateMachine();
QStateMachine machine;
public slots:
void Run();
void runS1();
void runS2();
void runS3();
void debugSlot();
};
#endif // TEST_H
test.cpp:
#include "test.h"
#include <iostream>
#include <QTextStream>
Test::Test(QObject * parent) : QObject(parent)
{
buildStateMachine();
}
void Test::Run()
{
QTextStream qin(stdin);
std::cout << "line: ";
QString line = qin.readLine();
if (line == "A")
{
std::cout << "emit stateChanged signal" << std::endl;
emit next_state();
}
else if (line == "q")
{
emit finished();
}
else
{
Run();
}
}
void Test::buildStateMachine()
{
QState *s1 = new QState(&machine);
QState *s2 = new QState(&machine);
QState *s3 = new QState(&machine);
s1->addTransition(this, SIGNAL(next_state()), s2);
s2->addTransition(this, SIGNAL(next_state()), s3);
s3->addTransition(this, SIGNAL(next_state()), s1);
connect(s1, &QState::entered, this, &Test::runS1);
connect(s2, &QState::entered, this, &Test::runS2);
connect(s3, &QState::entered, this, &Test::runS3);
machine.setInitialState(s1);
machine.start();
}
void Test::runS1()
{
std::cout << "entered state S1" << std::endl;
Run();
}
void Test::runS2()
{
std::cout << "entered state S2" << std::endl;
Run();
}
void Test::runS3()
{
std::cout << "entered state S3" << std::endl;
Run();
}
void Test::debugSlot()
{
std::cout << "debug slot was triggered!" << std::endl;
Run();
}
This problem is bothering me because it should work, but sadly it does not.
What i try to achieve is to read the standard output of a certain process and make another process handle it i.e. print it out.
The process that produces output looks like this:
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
int main() {
for (int i = 0; i < 100; i++) {
printf("yes %d\n",i);
fflush(stdout);
sleep(1);
}
return 0;
}
The process is started in another application like this:
#include <QProcess>
...
QProcess * process = new QProcess;
SomeClass * someClass = new SomeClass(process);
connect(process,SIGNAL(readyRead()),someClass,SLOT(onReadyRead()));
process->start("../Test/Test",QStringList());
if (!process->waitForStarted(4000)) {
qDebug() << "Process did not start.";
}
...
void SomeClass::onReadyRead() {
qDebug() << "Reading:" << process->readAllStdOutput();
}
My expected output would be:
Reading: yes 0
Reading: yes 1
...
Reading: yes 99
However i get no output at all.
And when i use QCoreApplication i get all the output but not through the signal/slot but directly in the console.
I dont understand because it works in another application that uses Qt 4.8.
My question is, is anyone experiencing the same problem or does anyone know how i can get the expected behaviour?
Your problem in the answer you provide lies in misunderstanding how the reading works. It simply returns whatever data you've got there, whether there are line endings or not. By spawning a thread and sleeping between lines, you're effectively sending the inter-process data in line-sized chunks since the pipe is flushed when you wait long enough.
So, your answer, while working, is not really how one should do it. You need to use readLine() to chop the incoming data into lines. Below is an example with following qualities:
There's just one executable :)
Only Qt apis are used. This reduces the runtime memory consumption.
Both processes cleanly terminate.
The amount of code is as minimal as practicable.
// https://github.com/KubaO/stackoverflown/tree/master/questions/process-17856897
#include <QtCore>
QTextStream out{stdout};
class Slave : public QObject {
QBasicTimer m_timer;
int m_iter = 0;
void timerEvent(QTimerEvent * ev) override {
if (ev->timerId() == m_timer.timerId()) {
out << "iteration " << m_iter++ << endl;
if (m_iter > 35) qApp->quit();
}
}
public:
Slave(QObject *parent = nullptr) : QObject(parent) {
m_timer.start(100, this);
}
};
class Master : public QObject {
Q_OBJECT
QProcess m_proc{this};
Q_SLOT void read() {
while (m_proc.canReadLine()) {
out << "read: " << m_proc.readLine();
out.flush(); // endl implicitly flushes, so we must do the same
}
}
Q_SLOT void started() {
out << "started" << endl;
}
Q_SLOT void finished() {
out << "finished" << endl;
qApp->quit();
}
public:
Master(QObject *parent = nullptr) : QObject(parent) {
connect(&m_proc, SIGNAL(readyRead()), SLOT(read()));
connect(&m_proc, SIGNAL(started()), SLOT(started()));
connect(&m_proc, SIGNAL(finished(int)), SLOT(finished()));
m_proc.start(qApp->applicationFilePath(), {"dummy"});
}
};
int main(int argc, char *argv[])
{
QCoreApplication app{argc, argv};
if (app.arguments().length() > 1)
new Slave{&app}; // called with an argument, this is the slave process
else
new Master{&app}; // no arguments, this is the master
return app.exec();
}
#include "main.moc"
Based on the code you've posted, you're connecting to the class slot with this: -
connect(process,SIGNAL(readyRead()),someClass,SLOT(onReadyReadStdOutput()));
But the function in the class is declared like this: -
void SomeClass::onReadyRead();
If you're expecting onReadyRead to be called, then you should be calling it in the SLOT, rather than onReadyReadStdOutput. So change your connection to: -
connect(process,SIGNAL(readyRead()),someClass,SLOT(onReadyRead()));
Well i solved my problem.
If the process is started with startDetached() it will not receive the signals from readyRead(), readyReadStandardOutput() and readyReadStandardError().
So just starting it with start() solved the problem.
However i noticed that if i start and do the while loop and prints in main() it will read everything at once even if it ends with \n. So i started the while loop in a thread and that problem was also solved. Everything prints as expected.
#include <QThread>
class Thread : public QThread
{
Q_OBJECT
public:
explicit Thread(QObject *parent = 0) : QThread(parent) {}
protected:
void run() {
for (int i = 0; i < 100; i++) {
std::cout << "yes" << i << std::endl;
msleep(200);
}
exit(0);
}
};
int main(int argc, char ** argv) {
QCoreApplication app(argc,argv);
Thread * t = new Thread();
t->start();
return app.exec();
}
TestP main.cpp
#include <QProcess>
#include <iostream>
class Controller : public QObject
{
Q_OBJECT
private:
QProcess * process;
public:
Controller(QObject *parent = 0) :
QObject(parent), process(new QProcess) {}
void init(const QString &program) {
connect(process,SIGNAL(readyRead()),this,SLOT(readStdOut()));
connect(process,SIGNAL(started()),this,SLOT(onStarted()));
connect(process,SIGNAL(finished(int)),this,SLOT(onFinished(int)));
process->start(program);
}
private slots:
void readStdOut() {
std::cout << "YES " << QString(process->readAllStandardOutput()).toUtf8().constData() << std::endl;
}
void onStarted(){
std::cout << "Process started" << std::endl;
}
void onFinished(int) {
std::cout << "Process finished: " << signal << std::endl;
}
};
int main(int argc, char *argv[]) {
QCoreApplication a(argc, argv);
Controller c;
c.init("../Test/Test");
return a.exec();
}
I'm trying to use QLocalServer as an ipc solution. The version of qt is 4.6
This is my main.cpp:
int main(int argc, const char*argv[]) {
QServer test();
while (true) {
}
}
This is my QServer class:
class QServer : public QObject
{
Q_OBJECT
public :
QServer ();
virtual ~QServer();
private :
QLocalServer* m_server;
QLocalSocket* m_connection;
private slots:
void socket_new_connection();
};
QServer::QServer()
{
m_server = new QLocalServer(this);
if (!m_server->listen("DLSERVER")) {
qDebug() << "Testing";
qDebug() << "Not able to start the server";
qDebug() << m_server->errorString();
qDebug() << "Server is " << m_server->isListening();
}
connect(m_server, SIGNAL(newConnection()),
this, SLOT(socket_new_connection()));
}
void
QServer::socket_new_connection()
{
m_connection = m_server->nextPendingConnection();
connect(clientConnection, SIGNAL(readyRead()),
this, SLOT(newData(clientConnection)));
}
This all compiles, however at runtime, when I try to connect newConnection(), I get a QSocketNotifier: Can only be used with threads started with QThread error.
I have tried wrapping this whole thing in a QThread, but I still got the same error.
Can anybody explain what I'm doing wrong or why there's even a thread involved?
The error message is misleading. You need a Qt event loop in order to use QSocketNotifier. The appropriate way to do that in your application is to create a QApplication (or if you don't want any graphical stuff, a QCoreApplication). Your main should look like:
int main(int argc, char** argv)
{
QCoreApplication app(argc, argv);
QServer test();
app.exec();
return 0;
}
QCoreApplication::exec() starts the event loop (which replaces your while (true) {} loop).