Emit Problems
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Hey, I was testing Qt out and was trying to do multi-threading with a simple test application to see how it would work. Well, I fast ran into the problem that either the Reader thread I created won't emit or the main application doesn't receive the signal. I've tried Googling my problem but didn't find anything that helped and I already spent a day trying to get this to work, so if anyone knows what I'm doing wrong I would appreciate the insight...
Qt Version: Qt 5.11.1 MSVC2017 64bit
Source: Gist
MyApp.cpp#include "MyApp.h" MyApp::MyApp(QWidget *parent) : QMainWindow(parent) { ui.setupUi(this); connect(&reader, SIGNAL(Done()), this, SLOT(done())); AllocConsole(); freopen("CONOUT$", "w", stdout); reader.start_reader(); } void MyApp::done() { std::cout << "Reader done!" << std::endl; }MyApp.h
#pragma once #include <iostream> #include <QtWidgets/QMainWindow> #include "ui_MyApp.h" #include "Reader.h" class MyApp : public QMainWindow { Q_OBJECT public: MyApp(QWidget *parent = 0); public slots: void done(); private: Ui::MyAppClass ui; Reader reader; };Reader.cpp
#include "Reader.h" Reader::Reader(QObject* parent) { abort = false; restart = false; } Reader::~Reader() { mutex.lock(); abort = true; condition.wakeOne(); mutex.unlock(); wait(); } void Reader::start_reader() { QMutexLocker locker(&mutex); if (isRunning()) { start(); } else { restart = true; condition.wakeOne(); } } void Reader::run() { emit Done(); }Reader.h
#pragma once #include <iostream> #include <QThread> #include <QMutex> #include <QWaitCondition> class Reader : public QThread { Q_OBJECT public: Reader(QObject *parent = 0); ~Reader(); void start_reader(); signals: void Done(); protected: void run() override; private: QMutex mutex; QWaitCondition condition; bool abort, restart; };PS: Sorry if this isn't the correct forum...
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Hey, I was testing Qt out and was trying to do multi-threading with a simple test application to see how it would work. Well, I fast ran into the problem that either the Reader thread I created won't emit or the main application doesn't receive the signal. I've tried Googling my problem but didn't find anything that helped and I already spent a day trying to get this to work, so if anyone knows what I'm doing wrong I would appreciate the insight...
Qt Version: Qt 5.11.1 MSVC2017 64bit
Source: Gist
MyApp.cpp#include "MyApp.h" MyApp::MyApp(QWidget *parent) : QMainWindow(parent) { ui.setupUi(this); connect(&reader, SIGNAL(Done()), this, SLOT(done())); AllocConsole(); freopen("CONOUT$", "w", stdout); reader.start_reader(); } void MyApp::done() { std::cout << "Reader done!" << std::endl; }MyApp.h
#pragma once #include <iostream> #include <QtWidgets/QMainWindow> #include "ui_MyApp.h" #include "Reader.h" class MyApp : public QMainWindow { Q_OBJECT public: MyApp(QWidget *parent = 0); public slots: void done(); private: Ui::MyAppClass ui; Reader reader; };Reader.cpp
#include "Reader.h" Reader::Reader(QObject* parent) { abort = false; restart = false; } Reader::~Reader() { mutex.lock(); abort = true; condition.wakeOne(); mutex.unlock(); wait(); } void Reader::start_reader() { QMutexLocker locker(&mutex); if (isRunning()) { start(); } else { restart = true; condition.wakeOne(); } } void Reader::run() { emit Done(); }Reader.h
#pragma once #include <iostream> #include <QThread> #include <QMutex> #include <QWaitCondition> class Reader : public QThread { Q_OBJECT public: Reader(QObject *parent = 0); ~Reader(); void start_reader(); signals: void Done(); protected: void run() override; private: QMutex mutex; QWaitCondition condition; bool abort, restart; };PS: Sorry if this isn't the correct forum...
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@kenchan Well, it was there the whole time under "Source: Gist" but I added it to code blocks as well.
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Hey, I was testing Qt out and was trying to do multi-threading with a simple test application to see how it would work. Well, I fast ran into the problem that either the Reader thread I created won't emit or the main application doesn't receive the signal. I've tried Googling my problem but didn't find anything that helped and I already spent a day trying to get this to work, so if anyone knows what I'm doing wrong I would appreciate the insight...
Qt Version: Qt 5.11.1 MSVC2017 64bit
Source: Gist
MyApp.cpp#include "MyApp.h" MyApp::MyApp(QWidget *parent) : QMainWindow(parent) { ui.setupUi(this); connect(&reader, SIGNAL(Done()), this, SLOT(done())); AllocConsole(); freopen("CONOUT$", "w", stdout); reader.start_reader(); } void MyApp::done() { std::cout << "Reader done!" << std::endl; }MyApp.h
#pragma once #include <iostream> #include <QtWidgets/QMainWindow> #include "ui_MyApp.h" #include "Reader.h" class MyApp : public QMainWindow { Q_OBJECT public: MyApp(QWidget *parent = 0); public slots: void done(); private: Ui::MyAppClass ui; Reader reader; };Reader.cpp
#include "Reader.h" Reader::Reader(QObject* parent) { abort = false; restart = false; } Reader::~Reader() { mutex.lock(); abort = true; condition.wakeOne(); mutex.unlock(); wait(); } void Reader::start_reader() { QMutexLocker locker(&mutex); if (isRunning()) { start(); } else { restart = true; condition.wakeOne(); } } void Reader::run() { emit Done(); }Reader.h
#pragma once #include <iostream> #include <QThread> #include <QMutex> #include <QWaitCondition> class Reader : public QThread { Q_OBJECT public: Reader(QObject *parent = 0); ~Reader(); void start_reader(); signals: void Done(); protected: void run() override; private: QMutex mutex; QWaitCondition condition; bool abort, restart; };PS: Sorry if this isn't the correct forum...
@Jeep said in Emit Problems:
if anyone knows what I'm doing wrong I would appreciate the insight...
Not yet. Remove the mutex and the condition and simplify. Call
wait()in the main window's destructor not in the thread's destructor, and instead of callingstart_reader()just callstart(). Most important of all make sure that the signal-slot connection is successful - use the pointer to member syntax there (Qt5 syntax) and check the return value.
