How to connect Qt combobox with pushbutton and some kind of widget that shows picture?
<p>I've just started to learn Qt and I want to make a simple program where I could select a picture name (in combobox) then click the pushbutton and selected picture would appear in widget(?) (in the same window if it's possible). 
<a href="https://i.stack.imgur.com/SbnEp.png" rel="nofollow noreferrer"><strong>It should look like this:</strong>
</a></p>

<p>The biggest problem that I've faced so far is connecting all those objects together, I can't make them work properly.</p>

<p>Also I've tried to upload picture to widget but it appears only in full size and my program becomes a picture and nothing else.</p>

<p>EDIT:</p>

<p>I am trying to make it work, but I can't achieve that..
<strong>That's my code:</strong></p>

<h2>mainwindow.cpp</h2>

<pre><code>#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui-&gt;setupUi(this);
}

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

void MainWindow::on_comboBox_currentIndexChanged(int index)
{
    connect(ui-&gt;comboBox, SIGNAL(currentIndexChanged(int index)), this, SLOT(on_pushButton_clicked(int index)));
}
void MainWindow::choiceChanged(int index)
{

    switch (index) {
    case 0:
    firstPicture();
    break;
    case 1:
    secondPicture();
    break;
    case 2:
    thirdPicture();
    break;
    }
}

void MainWindow::on_pushButton_clicked(int index)
{
    connect(ui-&gt;pushButton, SIGNAL(on_pushButton_clicked(int)), this, SLOT(choiceChanged(int)));
}
void MainWindow::firstPicture(){
    QPixmap image("C:/Documents/Aaaa.png");
    ui-&gt;label-&gt;setPixmap(image);
}
void MainWindow::secondPicture(){
    QPixmap image("C:/Documents/Bbbb.png");
    ui-&gt;label-&gt;setPixmap(image);
}
void MainWindow::thirdPicture(){
    QPixmap image("C:/Documents/Cccc.png");
    ui-&gt;label-&gt;setPixmap(image);
}
</code></pre>

<h2>main.cpp</h2>

<pre><code>#include "mainwindow.h"
#include &lt;QApplication&gt;

int main(int argc, char *argv[])
{

    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}
</code></pre>

<h2>mainwindow.h</h2>

<pre><code>#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include &lt;QMainWindow&gt;

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots: 
    void on_pushButton_clicked(int index);

    void choiceChanged(int index);

    void on_comboBox_currentIndexChanged(int index);

    void firstPicture();

    void secondPicture();

    void thirdPicture();

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H
</code></pre>