Clickable Pixmap class, problems with its parent

cppStudent012

Hi!

I am trying to make a Clickable Pixmap class which objects, once clicked, will open a QFileDialog to let the user choose another image to swap the current one.

Well, I can't really make this work, in particular how to initialize the parent of the class correctly.

Here's the code:

ClickablePixmap.h

#ifndef CLICKABLEPIXMAP_H
#define CLICKABLEPIXMAP_H

#include<QPixmap>
#include <QWidget>
#include <Qt>

class ClickablePixmap : QPixmap {
    Q_OBJECT

public:
    explicit ClickablePixmap(QWidget* parent = nullptr, Qt::WindowFlags f = Qt::WindowFlags());
    ~ClickablePixmap();
    void mousePressEvent(QMouseEvent* event);

signals:
    void clicked();

public slots:
    void ImageClicked();
};

#endif // CLICKABLEPIXMAP_H

ClickablePixmap.cpp

#include "clickablepixmap.h"
#include <QFileDialog>
#include <QDebug>

ClickablePixmap::ClickablePixmap(QWidget* parent, Qt::WindowFlags f) {
//how should I initialize the parent?
}

void ClickablePixmap::ImageClicked() {
    qDebug()<<"image_clicked";
    //how can I put here the parent of this object? (which is supposed to be instead of "this" )
    QString filename = QFileDialog::getOpenFileName(this, tr("Choose"), "", tr("Images(*.png *.jpg *.jpeg *.bmp)")); 
    if(QString::compare(filename, QString()) != 0)
    {
        QImage img;
        bool valid = img.load(filename);

        if(valid)
        {
            img = img.scaled(48,48);
        }
        else {
            //error handling
        }
    }
}

mahd96

why you need to initialize the parent in mouseEvent? i dont getting the purpose.

CP71

@cppStudent012 Hi,
I’m not sure that use Qpixmap derived class is the right choose.
When I have to do this use QWidget or its derived classes.

J.Hilk

hi @cppStudent012
QPixamp by default does not inherit QObject and/or QWidget,
-> there's no default Signal/Slot, mouseEvents or even a parent associated to it.

You would have to do this inside the Widget that is actually drawing/showing the pixmap

mrjj

Hi
I think something like
https://wiki.qt.io/Clickable_QLabel
will work better than Pixmap as base.

J.Hilk

@mrjj
that entry should be revised, makes my OCD tingle all over the place ;-)

cppStudent012

Thank you everyone for answering!

I tried to apply everyone suggestions and here is the final working code:

ClickablePixmap.h

#ifndef CLICKABLEPIXMAP_H
#define CLICKABLEPIXMAP_H

#include<QLabel>
#include<QPixmap>
#include <QWidget>
#include <Qt>

class ClickablePixmap : public QLabel {
    Q_OBJECT

public:
    explicit ClickablePixmap(QWidget* parent = nullptr, Qt::WindowFlags f = Qt::WindowFlags());
    ~ClickablePixmap();
    void mousePressEvent(QMouseEvent* event);

signals:
    void clicked();

public slots:
    void ImageClicked();
};

#endif // CLICKABLEPIXMAP_H

ClickablePixmap.cpp


#include "clickablepixmap.h"
#include <QFileDialog>

ClickablePixmap::ClickablePixmap(QWidget* parent, Qt::WindowFlags f) : QLabel(parent) {
    QPixmap img(":/Path_to_your_image");
    img = img.scaled(48,48);

    setPixmap(img);
}

ClickablePixmap::~ClickablePixmap() {}

void ClickablePixmap::mousePressEvent(QMouseEvent* event) {
    ImageClicked();
    emit clicked();
}

void ClickablePixmap::ImageClicked() {

    QString filename = QFileDialog::getOpenFileName(this, tr("Choose"), "", tr("Images(*.png *.jpg *.jpeg *.bmp)"));
    if(QString::compare(filename, QString()) != 0)
    {
        QImage img;
        bool valid = img.load(filename);

        if(valid)
        {
            img = img.scaled(48,48);
            setPixmap(QPixmap::fromImage(img));
        }
        else {
            //error handling
        }
    }
}

Thank you again everyone! :)

P.S. Any further improvement is always welcome. :)

mrjj

hi
I think you missed to send the parent to base class/ call base class constructor?
like
ClickablePixmap::ClickablePixmap(QWidget* parent, Qt::WindowFlags f) : QWidget(parent) {
...
}

J.Hilk

@cppStudent012
by making QWidget the base class and a QLabel the member, you make it more complicated than it has to be.

This way you'll have to apply a Layout or override the resizeEvent to align your QLabel correctly!

cppStudent012

Both suggested changes applied