Mapping signal via signalMapper

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Article Metadata

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Tested with

Devices(s): Emulator

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Compatibility

Platform(s): S60 3rd Edition FP1, S60 3rd Edition FP2, S60 5th Edition

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Article

Keywords: QSignalMapper

Created: mind_freak (21 Apr 2009)

Last edited: hamishwillee (11 Oct 2012)

Introduction

This example demonstrates how to use the QSignalMapper, a class for mapping parameterless signals from a set of objects to a single signal that contains a parameter identifying the original sending object.

Preconditions

• Download and install the Qt SDK

Source Code

Main.cpp

#include <QtGui/QApplication>
#include "buttonwidget.h"
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QStringList fonts;
     fonts << "Nokia" << "QT for S60" << "Python" << "J2ME";
    ButtonWidget w(fonts);
    w.show();
    return a.exec();
}

ButtonWidget.h

#ifndef BUTTONWIDGET_H
#define BUTTONWIDGET_H
 
#include <QtGui/QWidget>
#include<QSignalMapper>
#include<QPushButton>
#include<QGridLayout>
#include<QStringList>
class ButtonWidget : public QWidget
{
    Q_OBJECT
 
public:
    ButtonWidget(QStringList texts,QWidget *parent = 0);
 
signals:
    void clicked(const QString &text);
 
private:
    QSignalMapper *signalMapper;
};
 
#endif // BUTTONWIDGET_H

ButtonWidget.cpp

#include "buttonwidget.h"
 
ButtonWidget::ButtonWidget(QStringList texts,QWidget *parent)
    : QWidget(parent)
{
    signalMapper = new QSignalMapper();
 
    QGridLayout *gridLayout = new QGridLayout;
    for (int i = 0; i < texts.size(); ++i) {
        QPushButton *button = new QPushButton(texts[i]);
        connect(button, SIGNAL(clicked()), signalMapper, SLOT(map()));
        signalMapper->setMapping(button, texts[i]);
        gridLayout->addWidget(button, i / 3, i % 3);
    }
 
    connect(signalMapper, SIGNAL(mapped(const QString &)),
            this, SIGNAL(clicked(const QString &)));
 
    setLayout(gridLayout);
}
 
ButtonWidget::~ButtonWidget()
{
    if(signalMapper)
        delete signalMapper;
}

Explanation

A list of texts is passed to the constructor. A signal mapper is constructed and for each text in the list a QPushButton is created. We connect each button's clicked() signal to the signal mapper's map() slot, and create a mapping in the signal mapper from each button to the button's text. Finally we connect the signal mapper's mapped() signal to the custom widget's clicked() signal. When the user clicks a button, the custom widget will emit a single clicked() signal whose argument is the text of the button the user clicked.

ScreenShot

Related Links

Mapping of StandardItemModel via DataWidgetMapper in Qt