Qt5 Tutorial QComboBox - 2020

In this tutorial, we will learn QComboBox.

Qt->Qt Gui Application:

Let's make the UI as shown in the picture below.

Forms->comboboxdialog.ui:

Here are the codes.

ComboDialog.cpp:

#include "comboboxdialog.h"
#include "ui_comboboxdialog.h"

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

    // Fill the items of the ComboBox
    for(int i = 0; i < 10; i++)
    {
        ui->comboBox->addItem("item " + QString::number(i));
    }
}

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

// Message popup when the button is clicked
void ComboBoxDialog::on_pushButton_clicked()
{
    QMessageBox::information(this, "Item Selection",
                             ui->comboBox->currentText());
}

ComboDialog.h:

#ifndef COMBOBOXDIALOG_H
#define COMBOBOXDIALOG_H

#include <QDialog>
#include <QMessageBox>

namespace Ui {
class ComboBoxDialog;
}

class ComboBoxDialog : public QDialog
{
    Q_OBJECT
    
public:
    explicit ComboBoxDialog(QWidget *parent = 0);
    ~ComboBoxDialog();
    
private slots:
    void on_pushButton_clicked();

private:
    Ui::ComboBoxDialog *ui;
};

#endif // COMBOBOXDIALOG_H

First, we populated the items of the QComboBox.

ui->comboBox->addItem("item " + QString::number(i));

Then, when we click the button, a message box will popup to give information about the item that's currently selected. This message is not needed because the combo is already displaying the current item. But it's there for getting used to the QMessageBox as well as signals/slots.

QMessageBox::information(this, "Item Selection",
                             ui->comboBox->currentText());