Modify Qlabel value in Runtime

juaniyoalm

Hi, my problem is that when I modify the label in runtime, it doesn't change on window until the app is finished running. I want the label value to change on the window while the application is running.

Initial.cpp: (Window)

Initial::Initial() {
    widget.setupUi(this);
    
    // Conexíon de Observers
    connect(&mundo, SIGNAL(daysChange(const QString &)), this->widget.infoDiasLabel, SLOT(setText(const QString &)));
}

In World.h:

signals:
    void daysChange(const QString &);

In World.cpp

void World::downDays() {
    this->days--;
    emit daysChange(QString::number(this->days));
}

mrjj

@juaniyoalm
Hi and welcome
First check is to see if connect returns true.
Also,
connect(&mundo, ...
since you have to use & , its not a pointer so make sure its NOT running out of scope.
is mundo a member of class ?

Also,
did you remember
Q_OBJECT
for "World" class ?

Christian Ehrlicher

Is mundo and instance of World ? connect() returns a bool so you can check if the connect works as expected. I also would use the new signal/slot syntax - https://wiki.qt.io/New_Signal_Slot_Syntax

juaniyoalm

Thank you for yours answers.

@Mrjj

mundo is a member of class:
Initial.h

private:
    Ui::Initial widget;
    World mundo;
    int rows;
    int col;
    int nFungus;
    int days

and Q_Object is put:

World.h

class World : public QObject {
    Q_OBJECT

@Christian Ehrlicher

yes, mundo is instance of World.

And test connect is TRUE.

aha_1980

@juaniyoalm said in Modify Qlabel value in Runtime:

it doesn't change on window until the app is finished runnin

That sounds as if your event loop is blocked... impossible to tell from your snippet.

Christian Ehrlicher

@aha_1980 said in Modify Qlabel value in Runtime:

That sounds as if your event loop is blocked... impossible to tell from your snippet.

Or downDays() is not called at all - I would add a debug output there.

juaniyoalm

Put here all my code:

Initial.h


#ifndef _INITIAL_H
#define _INITIAL_H

#include "ui_Initial.h"
#include <QObject>
#include "World.h"

class Initial : public QMainWindow {
    Q_OBJECT
public:
    Initial();
    void tableFill();
    void init();
    virtual ~Initial();
    
public slots:
    void on_nHongosLineEdit( const QString & text );
    void buttonInitClick ();
    void satiateChanged(QString & text);
    void daysChanged(unsigned long);
   
private:
    Ui::Initial widget;
    World mundo;
    int rows;
    int col;
    int nFungus;
    int days;
};

#endif /* _INITIAL_H */

Initial.cpp


#include "Initial.h"
#include <QtGui>
#include <QMessageBox>
#include <QHeaderView>
#include <QStringList>
#include <iostream>


using namespace std;
Initial::Initial() {
    widget.setupUi(this);
    
    // Conexíon de Observers
    connect(this->widget.nHongosLineEdit,&QLineEdit::textEdited, this, &Initial::on_nHongosLineEdit);
    connect(this->widget.startButton,&QPushButton::clicked, this, &Initial::buttonInitClick);
    connect(&mundo, &World::daysChange, this->widget.infoDiasLabel, &QLabel::setText);

    // Validación de campos
    QIntValidator* validator = new QIntValidator(0, 500, this);
    this->widget.nFilasLineEdit->setValidator(validator);
    this->widget.nColumnasLineEdit->setValidator(validator);
    this->widget.nHongosLineEdit->setValidator(validator);
    this->widget.diasLineEdit->setValidator(validator);
    
    this->widget.tableWidget->horizontalHeader()->stretchLastSection();
    this->widget.infoHongosLabel->setText("0");
    this->widget.infoDiasLabel->setText("100");
}

void Initial::on_nHongosLineEdit(const QString& text)
{   
    if (this->widget.nHongosLineEdit->text().isEmpty() || (this->widget.nFilasLineEdit->text().toInt() *
            this->widget.nColumnasLineEdit->text().toInt()) < text.toInt()) {
        
        QMessageBox::warning(this,"Error","Hay más hongos que celdas");
        this->widget.nHongosLineEdit->setText("");
    }
}

void Initial::buttonInitClick() {
    // Conf world
    this->rows = this->widget.nFilasLineEdit->text().toInt();
    this->col = this->widget.nColumnasLineEdit->text().toInt();
    this->nFungus = this->widget.nHongosLineEdit->text().toInt();
    this->days = this->widget.diasLineEdit->text().toInt();
    
    // Info
    this->widget.infoHongosLabel->setText(QString::number(this->nFungus));
    //this->widget.infoDiasLabel->setText(QString::number(this->days));
       
    // Table
    this->widget.tableWidget->setRowCount(this->nFungus);
    this->widget.tableWidget->setColumnCount(4);
    QStringList labels = {"Id", "Place", "Status", "Saciate level"};
    this->widget.tableWidget->setHorizontalHeaderLabels(labels);
   
    // Init Wolrd
    
    
    this->mundo.createWorld(rows, col, nFungus, days);
    tableFill();
    //this->mundo.initializeWorld();
    init();
}

void Initial::init() {
    this->mundo.initializeWorld();
}


void Initial::satiateChanged(QString & text) {
    cout << "HONGO CAMBIADO" << text.toStdString() << endl;
}

void Initial::daysChanged(unsigned long value) {
    cout << "DIA CAMBIADO" << value << endl;
    this->widget.infoDiasLabel->setText(QString::number(value));
}

void Initial::tableFill() {
    
    for(int j = 0; j < mundo.getAllFungusSize(); j++) {
        this->widget.tableWidget->setItem(j, 0, new QTableWidgetItem(QString::number(mundo.getFungusByPosition(j)->getId())));
        this->widget.tableWidget->setItem(j, 1, new QTableWidgetItem("[" + QString::number(mundo.getFungusByPosition(j)->getPlace().first) +
                ", " + QString::number(mundo.getFungusByPosition(j)->getPlace().second) + "]"));
        this->widget.tableWidget->setItem(j, 2, new QTableWidgetItem(QString::number(mundo.getFungusByPosition(j)->getAge())));
        this->widget.tableWidget->setItem(j, 3, new QTableWidgetItem(QString::number(mundo.getFungusByPosition(j)->isSaciate())));
    }
}

Initial::~Initial() {
}

World.h

#ifndef WORLD_H
#define WORLD_H

#include <vector>
#include "Fungus.h"
#include "Cell.h"
#include <QObject>

using namespace std;
// Tipos definidos que permiten la creación de la matriz (World)
typedef vector<vector<Cell*>> AllWorld;

class World : public QObject {
    Q_OBJECT
public:
    unsigned long days; // Días que durará el mundo.
    World(); // Constructor de World por defecto.
    World(unsigned long, unsigned long, unsigned long, unsigned long); // Constructor de World sobrecargado.
    void createWorld(unsigned long, unsigned long, unsigned long, unsigned long); // Crea un mundo.
    void distributeFungus(unsigned long, unsigned long); // Distribuye aleatoriamente los hongos en el mundo.
    void initializeWorld(); // Inicializa el mundo. 
    AllWorld getWorld(); // Devuelve el mundo.
    vector<Fungus*> getAllFungus(); // Devuelve un array de punteros a los hongos.
    int getAllFungusSize(); // Devuelve el número de hongos totales.
    unsigned long rowSize(); // Número de filas de la matriz (World).
    unsigned long columnSize(); // Número de columnas de la matriz (World).
    Fungus* getFungusByPosition(unsigned long); // Devuelve un hongo dada una posicion del array de punteros.
    int areLimit(std::pair<unsigned long, unsigned long> place); // Devuelve en qué límite se encuentra el hongo (0 para no límite).
    int moveType(Fungus*, int); // Comprueba en que celda hay comida y devuelve un movimiento.
    Cell* getCell(int, int); // Devuelve un puntero a una celda del mundo.
    void assignMove(int, Cell*, Fungus*); // Mueve un hongo de celda.
    void downDays(); // Decrementa un día.
    virtual ~World(); // Destructor de World por defecto.

signals:
    void daysChange(const QString &);
    
private:
    AllWorld world; // Matriz que contiene todas las celdas (Mundo).
    vector<Fungus> allFungus; // Array de hongos.
};

#endif /* WORLD_H */

World.cpp (Only method that emit)

void World::downDays() {
    this->days--;
    emit daysChange(QString::number(this->days));
}

The same application but with the console output is correct.

mrjj

Hi
Code looks fine and you used new syntax so it clearly accepts the connect.
I see no loops that would strangulate updates so we need to find out if it tried to emit

can you hook up
void World::downDays() {
this->days--;
emit daysChange(QString::number(this->days));
qDebug() << "downDays called";
}

to see if it tries to emit at all ?

juaniyoalm

@mrjj

I have tried the code that you have put me and emits well. There is a While loop. This loop, at the end of each iteration, calls the daysDown () method but it works fine, in each iteration it shows "downDays called"

aha_1980

@juaniyoalm said in Modify Qlabel value in Runtime:

There is a While loop. This loop, at the end of each iteration, calls the daysDown () method but it works fine, in each iteration it shows "downDays called"

Yeah, but the emit is processed once the event loop is free running - which is not the case in your while loop.

Try replacing the loop with some QTimer, for example.

Edit: it is rather the repainting of the GUI that is processed when the event loop is running.

juaniyoalm

@aha_1980

Thank you for your answer.

Sorry but I'm starting to use Qt and I'm not going to use it well yet. How do I substitute the while loop for QTimer?

mrjj

@juaniyoalm
Hi
before changing to a timer, you could try inserting
QApplication::processEvents();
( its static )
in the loop just after calling daysDown()
This drives the event loop and if it updates, its clear it was strangulating the event loop.
Please note however, its not the optimal / recommended way of fixing it.
Its just to test we found the guilty section :)

aha_1980

@juaniyoalm

Something like this (only brain compiled):

// world.h
#include <QTimer>

class World : public QObject {
// ...

public slots:
 void downDays();

private:
  QTimer *m_timer;
}

// world.cpp

m_timer = new QTimer(this);
m_timer->setTimeout(1000);
connect(m_timer, &QTimer::timeout, this, &World::downDays);
m_timer->start();

juaniyoalm

@mrjj

I've inserted QApplication::processEvents() and the app works fine now!!

What would be the correct way to do it?

aha_1980

@juaniyoalm using a QTimer ;)

juaniyoalm

@aha_1980

Qtimer class hasn't a member named setTimeout...

aha_1980

@juaniyoalm sorry, use setInterval

juaniyoalm

@aha_1980

I used setInterval but the app does not work fine. I have placed it in the constructor.

This is my code:

Initial.cpp (Window)

Initial::Initial() {
    widget.setupUi(this);
   
    // Conexíon de Observers
    connect(this->widget.nHongosLineEdit,&QLineEdit::textEdited, this, &Initial::on_nHongosLineEdit);
    connect(this->widget.startButton,&QPushButton::clicked, this, &Initial::buttonInitClick);
    connect(&mundo, &World::daysChange, this->widget.infoDiasLabel, &QLabel::setText);  
    connect(&mundo, &World::daysChange, this, &Initial::daysChanged);
    
    m_timer = new QTimer(this);
    m_timer->setInterval(1000);
    connect(m_timer, &QTimer::timeout, this, &Initial::daysChanged);
    m_timer->start();
    
    // Validación de campos
    QIntValidator* validator = new QIntValidator(0, 500, this);
    this->widget.nFilasLineEdit->setValidator(validator);
    this->widget.nColumnasLineEdit->setValidator(validator);
    this->widget.nHongosLineEdit->setValidator(validator);
    this->widget.diasLineEdit->setValidator(validator);
    
    this->widget.tableWidget->horizontalHeader()->stretchLastSection();
    this->widget.tableWidget->verticalHeader()->setVisible(false);
    this->widget.infoHongosLabel->setText("0");
    this->widget.infoDiasLabel->setText("100");
}

Initial.h


class Initial : public QMainWindow {
    Q_OBJECT
public:
    Initial();
    void tableFill();
    void init();
    virtual ~Initial();
    
public slots:
    void on_nHongosLineEdit( const QString & text );
    void buttonInitClick ();
    void daysChanged();
   
private:
    Ui::Initial widget;
    World mundo;
    int rows;
    int col;
    int nFungus;
    int days;
    QTimer *m_timer;
};

World.cpp (Only loop)

 while (this->days != 0) {
        
        cout << endl;
        cout << "----------------------------------" << endl;
        cout << "QUEDA(N) " << this->days << " DIA(S) " << endl;
        cout << "----------------------------------" << endl;
    
        // Recorremos todos los hongos de los que disponemos.
        for (unsigned long i = 0; i < this->allFungus.size(); i++) {
            fungus = getFungusByPosition(i);

            // Si el hongo esta COMPLETAMENTE saciado, reestablecemos su saciedad.
            if (fungus->getSatiate() == 5)
                fungus->setSatiate(0);

            cell = getCell(fungus->getPlace().first, fungus->getPlace().second);

            // Mientras que el hongo no este saciado...
            while (!fungus->isSaciate()) {
                if (cell->thereIsFood()) { // Si la celda tiene comida...
                    cout << "La celda (" << fungus->getPlace().first << ", " << fungus->getPlace().second << ")" << " tiene comida" << endl;
                    cell->feed();
                    fungus->feed();
                    cout << "El hongo con id " << fungus->getId() << " se come una unidad de la celda situada en la coordenada (" << fungus->getPlace().first << ", " << fungus->getPlace().second << ")" << endl;
                    if (fungus->isSaciate()){
                        cout << "El hongo con id " << fungus->getId() << " esta saciado" << endl;
                        cout << endl;
                    }
                } else { // Si la celda no tiene comida...
                    cout << "No hay comida en la celda " << fungus->getPlace().first << ", " << fungus->getPlace().second << endl;               
                    // Identificamos el movimiento del hongo.
                    int move = moveType(fungus, areLimit(std::pair<unsigned long, unsigned long>(fungus->getPlace().first, fungus->getPlace().second)));
                    // Realizamos el movimiento del hongo.    
                    assignMove(move, cell, fungus);
                    cout << "El hongo " << fungus->getId() << " se ha movido a la coordenada " << fungus->getPlace().first << ", " << fungus->getPlace().second << endl;
                    if(!cell->thereIsFood()) break;   
                } // Fin del condicional HAY COMIDA
            } // Fin del WHILE SACIADO
        }  // Fin del FOR
        // Decrementamos los días
        downDays();  
        //QApplication::processEvents();
    } // Fin del WHILE DÍAS

World.h

using namespace std;
// Tipos definidos que permiten la creación de la matriz (World)
typedef vector<vector<Cell*>> AllWorld;

class World : public QObject {
    Q_OBJECT
public:
    unsigned long days; // Días que durará el mundo.
    World(); // Constructor de World por defecto.
    World(unsigned long, unsigned long, unsigned long, unsigned long); // Constructor de World sobrecargado.
    void createWorld(unsigned long, unsigned long, unsigned long, unsigned long); // Crea un mundo.
    void distributeFungus(unsigned long, unsigned long); // Distribuye aleatoriamente los hongos en el mundo.
    void initializeWorld(); // Inicializa el mundo. 
    AllWorld getWorld(); // Devuelve el mundo.
    vector<Fungus*> getAllFungus(); // Devuelve un array de punteros a los hongos.
    int getAllFungusSize(); // Devuelve el número de hongos totales.
    unsigned long rowSize(); // Número de filas de la matriz (World).
    unsigned long columnSize(); // Número de columnas de la matriz (World).
    Fungus* getFungusByPosition(unsigned long); // Devuelve un hongo dada una posicion del array de punteros.
    int areLimit(std::pair<unsigned long, unsigned long> place); // Devuelve en qué límite se encuentra el hongo (0 para no límite).
    int moveType(Fungus*, int); // Comprueba en que celda hay comida y devuelve un movimiento.
    Cell* getCell(int, int); // Devuelve un puntero a una celda del mundo.
    void assignMove(int, Cell*, Fungus*); // Mueve un hongo de celda.
    void downDays(); // Decrementa un día.
    virtual ~World(); // Destructor de World por defecto.

signals:
    void daysChange(const QString &);
    
private:
    AllWorld world; // Matriz que contiene todas las celdas (Mundo).
    vector<Fungus> allFungus; // Array de hongos.
    double timeExecute;
};

aha_1980

@juaniyoalm Well, the blocking loop is still there.

You need to move the loop body into a slot and call that slot from the QTimers timeout signal. When this->days == 0, you stop the timer. Should be pretty straight forward.