Qcombobox

[arturs]

Hi

I have QCombox without items. After clicking on the combobox I would like to showmessage but I cannot find slot "Clicked" or something similar.

How to do it ?

Regards
Artur

[wysota]

There is no such signal. If you want to have one, subclass, reimplement mouse events and emit such signal yourself.

[chris.kzn]

... in short, add a pushButton, eish, that is just mean - lol.

[Radek]

No. Do as Wysota has said. The mouse event will hook clicking the combo box and emit a "clicked" signal - perhaps only sometimes (when the combo box is empty). If the combo box isn't empty, you get a signal from the clicked item.

[arturs]

If it is not problem please give me an example.

Thank you for help

[wysota]

If it is not problem please give me an example.

An example of what?

[arturs]

How to do it using QMouseEvent.
How to determine that the left button of mouse was clicked on the Combobox.

[wysota]

How to do it using QMouseEvent.
How to determine that the left button of mouse was clicked on the Combobox.

void Combo::mousePressEvent(QMouseEvent *e) {
  if(e->button() == Qt::LeftMouseButton) emit clicked();
}

void Combo::mousePressEvent(QMouseEvent *e) {
  if(e->button() == Qt::LeftMouseButton) emit clicked();
}

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[arturs]

My Code

void Test::mouseMoveEvent(QMouseEvent *event)
{
    if (event->button()==Qt::LeftButton) emit clicked();
 
}

void Test::mouseMoveEvent(QMouseEvent *event)
{
    if (event->button()==Qt::LeftButton) emit clicked();

}

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Should I create clicked signal ? because Now I have the following error: 'clicked' was not declared in this scope

[wysota]

Should I create clicked signal ?

If you want to emit a signal, the signal has to exist. So yes, you need to declare the signal in your class.

[arturs]

but It is still not clear for me. The signal will be sent each time when the left button of mouse is clicked even if the pointer of mouse there is out of Combobox area.

Second question:
Is it possible to check using a method if a slot was called by signal or was called another method

for example:


I have a slot

void Test:: test1 (void) {
 
qDebug () << "TEST";
}

void Test:: test1 (void) {

qDebug () << "TEST";
}

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I can call it using the following code:
test();

or it can be called by signal.

I would like to know which method was used to call the slot.

[wysota]

but It is still not clear for me. The signal will be sent each time when the left button of mouse is clicked even if the pointer of mouse there is out of Combobox area.

No. A widget receives mouse events only when they happen over its area.

Is it possible to check using a method if a slot was called by signal or was called another method

QObject::sender()

I would like to know which method was used to call the slot.

What for?

[arturs]

As I thought It did not work something is wrong

My code:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMouseEvent>
#include <QDebug>
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QObject::connect(ui->comboBox,SIGNAL(clicked()),this,SLOT(test()));
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
 
void MainWindow::mouseMoveEvent(QMouseEvent *event)
{
    if (event->button()==Qt::LeftButton) emit clicked();
 
}
 
 
void MainWindow::test (void){
 
    qDebug () << "TEST SIGNAL";
 
 
}

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

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QObject::connect(ui->comboBox,SIGNAL(clicked()),this,SLOT(test()));
}

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


void MainWindow::mouseMoveEvent(QMouseEvent *event)
{
    if (event->button()==Qt::LeftButton) emit clicked();

}


void MainWindow::test (void){

    qDebug () << "TEST SIGNAL";


}

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#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();
    void mouseMoveEvent(QMouseEvent *);
    void test (void);
signals:
    void clicked(void);
 
private:
    Ui::MainWindow *ui;
};
 
#endif // 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();
    void mouseMoveEvent(QMouseEvent *);
    void test (void);
signals:
    void clicked(void);

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

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No. A widget receives mouse events only when they happen over its area.


QObject::sender()

What for?

I have a method open_file and in the first case I choose proper file from C: disk (QfileDialog) in second case the same file is downloaded from server and write for example on C: disk.
In second case I know file path so I do not know to choose file once again but used path which was chosen before writing file.

How to skip the part of code which open Qfiledialog.

Regards
Artur

[wysota]

void MainWindow::mouseMoveEvent(QMouseEvent *event)
{
    if (event->button()==Qt::LeftButton) emit clicked();
 
}

void MainWindow::mouseMoveEvent(QMouseEvent *event)
{
    if (event->button()==Qt::LeftButton) emit clicked();

}

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First of all this is a handler for mouseMoveEvent for which button() always returns 0 (obviously a move is not caused by a button). Second of all this is an event handler for MainWindow and not the combobox.

I have a method open_file and in the first case I choose proper file from C: disk (QfileDialog) in second case the same file is downloaded from server and write for example on C: disk.
In second case I know file path so I do not know to choose file once again but used path which was chosen before writing file.

How to skip the part of code which open Qfiledialog.

Why don't you store the path in some variable and if the variable is not empty you will know you already have the path?

[arturs]

I made a mistake. I do not know Why I used Mosemove...

void QComboBox::mousePressEvent(QMouseEvent *event)
{
    if (event->button()==Qt::LeftButton) emit clicked();
 
}

void QComboBox::mousePressEvent(QMouseEvent *event)
{
    if (event->button()==Qt::LeftButton) emit clicked();

}

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but know I have the error: 'clicked' was not declared in this scope

something is wrog I am a bit confused

[wysota]

You cannot define a handler for a class which already exists. You need to subclass QComboBox and use an instance of your subclass instead of QComboBox. Alternatively you can apply an event filter on the existing combobox if you want to avoid subclassing however this will make your code messy.

[arturs]

I created the following code:

#include "mycombobox.h"
 
MyCombobox::MyCombobox(QWidget *parent) : QComboBox(parent)
{
 
}
 
MyCombobox::~MyCombobox()
{
 
}
 
void MyCombobox::mousePressEvent(QMouseEvent *event)
{
 
    if (event->button()==Qt::LeftButton) emit clicked();
 
}

#include "mycombobox.h"

MyCombobox::MyCombobox(QWidget *parent) : QComboBox(parent)
{

}

MyCombobox::~MyCombobox()
{

}

void MyCombobox::mousePressEvent(QMouseEvent *event)
{

    if (event->button()==Qt::LeftButton) emit clicked();

}

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#ifndef MYCOMBOBOX_H
#define MYCOMBOBOX_H
 
#include <QObject>
#include <QWidget>
#include <QComboBox>
#include <QMouseEvent>
 
class MyCombobox : public QComboBox
{
    Q_OBJECT
 
public:
    MyCombobox(QWidget *parent =0 );
    ~MyCombobox();
 
protected:
 
    void mousePressEvent(QMouseEvent *);
 
signals:
 
    void clicked(void);
 
};
 
#endif // MYCOMBOBOX_H

#ifndef MYCOMBOBOX_H
#define MYCOMBOBOX_H

#include <QObject>
#include <QWidget>
#include <QComboBox>
#include <QMouseEvent>

class MyCombobox : public QComboBox
{
    Q_OBJECT

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

protected:

    void mousePressEvent(QMouseEvent *);

signals:

    void clicked(void);

};

#endif // MYCOMBOBOX_H

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but something is wrong I have the following errors: undefined reference to `vtable for MyCombobox' and I do not know what is wrong

Thank you for your patience

[wysota]

Do you mean the solution ?

I don't understand what you mean. Does it work?

[arturs]

I edited my previous post because I sent it by my mistake

[Radek]

I do not know what is wrong, either. IMO, the code should work. Try:
(1) Remove QObject and QWidget includes - they are included by QComboBox
(2) Add "virtual" specifiers to the dtor and the mouse handler. Well, you need not according to the C++ specification - because both methods are already virtual.
(3) Remove the "void" parameter from clicked(). Well, the "old" syntax is still legal but contemporary C++ is rather "clicked()" than "clicked(void)"
(3) If it does not help, delete the compiled files directory and make Creator to build everything from (real) scratch.