CODEWITHSUNDEEP
c++qtdialogsignals-slots
fs_tigre
fs_tigre

Reputation: 10738

Using Signals and Slots to Comunicate a QDialog with MainWindow in Qt

Ok I think is time to get some help, I have been practicing with signals and slots in Qt and I got stocked. What I want is to be able to change a label in mainwindow when a button in a QDialog is clicked. I have been searching and apparently the only way to do this is basically using signals and slots, here is what I have...

I have a mainwindow.ui with a button called "pushButton_OpenWindow" and a QLabel label_ShowText", I also have a externaldialog.ui that contains a QLineEdit called lineEdit_ExternalInput" and a QPushButton called "pushButton_SendText", and what I want is to change "label_ShowText" to whatever value "lineEdit_ExternalInput" is when pushButton_SendText" is clicked but it doesn't work, when I click the button nothing happens no errors, no warnings nothing.

Here is the code that doesn't work...

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void on_pushButton_OpenWindow_clicked();
    void textValue(const QString &newText);

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "externaldialog.h"
#include <QDebug>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    ExternalDialog *externalDialog = new ExternalDialog;
    // connecting signals and slots
    QObject::connect(externalDialog, SIGNAL(textChanged(QString)), this, SLOT(textValue(QString)));
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::on_pushButton_OpenWindow_clicked()
{
    ExternalDialog mDialog;
    mDialog.setModal(true);
    mDialog.exec();
}

void MainWindow::textValue(const QString &newText)
{
    ui->label_ShowText->setText(newText);
    qDebug()<<"Message from textValue Function \n";
}

externaldialog.h

#ifndef EXTERNALDIALOG_H
#define EXTERNALDIALOG_H

#include <QDialog>

namespace Ui {
class ExternalDialog;
}

class ExternalDialog : public QDialog
{
    Q_OBJECT

public:
    explicit ExternalDialog(QWidget *parent = 0);
    ~ExternalDialog();

private:
    Ui::ExternalDialog *ui;

signals:
     void textChanged(const QString&);
public slots:
     void on_pushButton_SendText_clicked();
};

#endif // EXTERNALDIALOG_H

externaldialog.cpp

#include "externaldialog.h"
#include "ui_externaldialog.h"
#include <QDebug>


ExternalDialog::ExternalDialog(QWidget *parent) :
    QDialog(parent),
    ui(new Ui::ExternalDialog)
{
    ui->setupUi(this);

}

ExternalDialog::~ExternalDialog()
{
    delete ui;
}


void ExternalDialog::on_pushButton_SendText_clicked()
{
    emit textChanged(ui->lineEdit_ExternalInput->text());
    qDebug()<<"Sent Message";
}

main.cpp

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

Any idea what I'm I doing wrong? Any suggestion will be appreciated. Sorry I posted the whole code but sometimes is better to see the whole picture.

Thanks a lot

Upvotes: 2

Views: 8142

Answers (1)

Jay
Jay

Reputation: 1077

change function MainWindow::on_pushButton_OpenWindow_clicked() into this

void MainWindow::on_pushButton_OpenWindow_clicked()
{
    externalDialog->setModal(true);
    externalDialog->exec();
}

You have just create a new unconnected dialog in the original function.

Upvotes: 6

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