Mapping signal via signalMapper

From Forum Nokia Wiki

ID	...	Creation date	21 April 2009
Platform	S60 3rd Edition FP1, S60 3rd Edition FP2, S60 5th Edition	Tested on devices	Emulator
Category	Qt for S60	Subcategory	Application

Keywords (APIs, classes, methods, functions): QSignalMapper,QPushButton

Introduction

he QSignalMapper class bundles signals from identifiable senders.

This class collects a set of parameterless signals, and re-emits them with integer, string or widget parameters corresponding to the object that sent the signal.

Preconditions

Download and Install latest version Qt for Symbian - Installation packages which has links on how to install the latest version

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

More about QSignalMapper.

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