[Solved] Signals and Slots help needed

amban

Hi All,
I have written this code where i have created a from which takes input from a line edit and when a QPushButton is clicked, the slot buttonClicked() must be called which does some work. I initially used Qt Designer so it was very easy, where i had to right-click , "go to slot" and write the code there. Please help me out.

widget.h

@#ifndef WIDGET_H
#define WIDGET_H

#include <QtGui/QWidget>
#include <QTabWidget>
#include <QWidget>
#include <QtGui>

class Widget : public QWidget
{
Q_OBJECT

public:
Widget(QWidget *parent = 0);
~Widget();

public slots:
void buttonClicked();

private:
QLineEdit *enterjobid;
QPushButton *viewbutton;
QPushButton *clearbutton;
QMessageBox *jobmessagebrowser;
};@

widget.cpp

@#include "widget.h"

Widget::Widget(QWidget *parent)
: QWidget(parent)
{
QVBoxLayout *mainLayout = new QVBoxLayout;

QHBoxLayout *row1 = new QHBoxLayout;
QLabel *jobid = new QLabel(tr("Enter Job ID"));
QLineEdit *enterjobid = new QLineEdit;
row1->addWidget(jobid);
row1->addWidget(enterjobid);

QHBoxLayout *row2 = new QHBoxLayout;
QPushButton *viewbutton = new QPushButton(tr("View Job Messages"));
QPushButton *clearbutton = new QPushButton(tr("Clear"));
row2->addWidget(viewbutton);
row2->addWidget(clearbutton);

QTextBrowser *jobmessagebrowser = new QTextBrowser;
mainLayout->addLayout(row1);
mainLayout->addLayout(row2);
mainLayout->addWidget(jobmessagebrowser);
setLayout(mainLayout);

connect (clearbutton,SIGNAL(clicked()),
         enterjobid,SLOT(clear()));

connect (viewbutton,SIGNAL(clicked()),
          this ,SLOT(buttonClicked()));

}

void Widget::buttonClicked()
{
connect (viewbutton,SIGNAL(clicked()),
enterjobid,SLOT(selectAll()));
// some work
}@

main.cpp

@#include <QtGui/QApplication>
#include "widget.h"

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

return a.exec(&#41;;

}@

lgeyer

So... what exactly is your problem?

The code you have written for buttonClicked() might not do what you possibly expect (calling enterjobid->selectAll()), as the connection between viewbutton->clicked() and enterjobid->selectAll() ist not yet established at the time the clicked() signal is emitted (however, this will work the second time you click the button).

If you just want to "call" a slot there is no need for a connection. Slots are ordinary functions which can be called through connections, but do not have to. So to select all in enterjobid just use
@
void Widget::buttonClicked()
{
enterjobid->selectAll();
// some work
}@

aureshinite

@
void Widget::buttonClicked()
{
connect (viewbutton,SIGNAL(clicked()),
enterjobid,SLOT(selectAll()));
// some work
}
@

Why do you do that???
edit: Your description of what you want to do is a bit unclear too.

amban

The problem is when i run the above code. The clear button works fine but when i click the viewbutton, the application output says - "The program has unexpectedly finished". I made above changes but got the same behavior.

amban

Ok i generate the above form with a QLabel, QLineEdit, QPushbutton and a QTExtBrowser. When i will click "viewbutton" , i want to grab all the input from the lineedit, search for it and print a message in the textbrowser as "Job found" / "not found"

Also i have a clear button which clears off contents of lineedit. It works fine using simple signal/slot mechanism.

amban

Hi All,
I solved it out. It was failing because of incorrect declarations. The final code is :

widget.h

@class Widget : public QWidget
{
Q_OBJECT

public :
Widget(QWidget *parent = 0);

private slots:
void buttonClicked();

private:
QLineEdit *enterjobid;
QPushButton *viewbutton;
QTextBrowser *jobmessagebrowser;
};
@

widget.cpp

@Widget::Widget(QWidget *parent)
:QWidget(parent)
{

QVBoxLayout *mainLayout = new QVBoxLayout;

QHBoxLayout *row1 = new QHBoxLayout;
QLabel *jobid = new QLabel(tr("Enter Job ID"));
enterjobid = new QLineEdit;
row1->addWidget(jobid);
row1->addWidget(enterjobid);

QHBoxLayout *row2 = new QHBoxLayout;
viewbutton = new QPushButton(tr("View Job Messages"));
QPushButton *clearbutton = new QPushButton(tr("Clear"));
row2->addWidget(viewbutton);
row2->addWidget(clearbutton);

jobmessagebrowser = new QTextBrowser;
mainLayout->addLayout(row1);
mainLayout->addLayout(row2);
mainLayout->addWidget(jobmessagebrowser);
setLayout(mainLayout);

connect (clearbutton,SIGNAL(clicked()),
         enterjobid,SLOT(clear()));

connect (viewbutton,SIGNAL(clicked()),
          this ,SLOT(buttonClicked()));

}

void Widget::buttonClicked()
{
connect (viewbutton,SIGNAL(clicked()),
enterjobid,SLOT(selectAll()));

//some work

}
@

Hope this helps out someone.
Thanks.

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[Solved] Signals and Slots help needed