Load image in custom QGraphicsView

hobbyProgrammer

Hi,
I am trying to load an image (QPixmap) into a custom QGraphicsView.
I made a design using the .ui form and promoted the GraphicsView to my custom graphicsView.
It allows me to select a photo, but the photo is not visible in the GraphicsView.
Is there anyone who knows what this problem is?

this is the code:

mainwindow.h:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QGraphicsView>
#include <QGraphicsScene>
#include <QScrollArea>
#include <QGraphicsPixmapItem>
#include <QGraphicsPolygonItem>
#include <QGraphicsItem>
#include <QFileDialog>
#include <QDir>

#include <QDebug>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

protected slots:
    void openPhoto();
private slots:
    void on_pushButton_clicked();

private:
    Ui::MainWindow *ui;
    void createMenus();
    void createActions();

    QMenu *fileMenu;
    QMenu *optionMenu;

    QAction *openAct;
    QAction *exitAct;
    QAction *clearScreenAct;
    QAction *undoAct;
    QAction *redoAct;
    QAction *addRoomAct;
    QAction *zoomInAct;
    QAction *zoomOutAct;

    QGraphicsScene *scene;

};
#endif // MAINWINDOW_H

mainwindow.cpp:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "graphicsview.h"

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

    createActions();
    createMenus();

    scene = new QGraphicsScene();


}

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

void MainWindow::createActions()
{
    openAct = new QAction(tr("&Open..."), this);
    openAct->setShortcuts(QKeySequence::Open);
    connect(openAct, SIGNAL(triggered()), this, SLOT(openPhoto()));

    exitAct = new QAction(tr("&Exit"), this);
    exitAct->setShortcuts(QKeySequence::Quit);
    connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));
}

void MainWindow::createMenus()
{

}

void MainWindow::openPhoto()
{
    QString fileName;
    fileName = QFileDialog::getOpenFileName(this, tr("Open File"), QDir::currentPath());
    if(!fileName.isNull() || !fileName.isEmpty())
    {
        graphicsView gv;
        gv.openPhoto(fileName);
    }
}

void MainWindow::on_pushButton_clicked()
{
    openPhoto();
}

graphicsview.h:

#ifndef GRAPHICSVIEW_H
#define GRAPHICSVIEW_H

#include <QWidget>
#include <QGraphicsView>

class graphicsView : public QGraphicsView
{
    Q_OBJECT
public:
    explicit graphicsView(QWidget *parent = nullptr);
    void openPhoto(QString);
signals:

public slots:

private:
    QGraphicsScene *scene;
};

#endif // GRAPHICSVIEW_H

graphicsview.cpp:

#include "graphicsview.h"

graphicsView::graphicsView(QWidget *parent) : QGraphicsView(parent)
{
    scene = new QGraphicsScene();
    this->setScene(scene);
    this->setAlignment(Qt::AlignLeft | Qt::AlignTop);
}

void graphicsView::openPhoto(QString filename)
{
    scene->addPixmap(QPixmap(filename));
    this->setScene(scene);
}

jsulm

@hobbyProgrammer said in Load image in custom QGraphicsView:

graphicsView gv;

You're creating a LOCAL instance of graphicsView which is NOT used anywhere afterwards...

hobbyProgrammer

made the code working...
this is what it looks like now:

mainwindow.h:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QGraphicsView>
#include <QGraphicsScene>
#include <QScrollArea>
#include <QGraphicsPixmapItem>
#include <QGraphicsPolygonItem>
#include <QGraphicsItem>
#include <QFileDialog>
#include <QDir>

#include <QDebug>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

protected slots:
    void openPhoto();
private slots:
    void on_pushButton_clicked();

private:
    Ui::MainWindow *ui;
    void createMenus();
    void createActions();

    QMenu *fileMenu;
    QMenu *optionMenu;

    QAction *openAct;
    QAction *exitAct;
    QAction *clearScreenAct;
    QAction *undoAct;
    QAction *redoAct;
    QAction *addRoomAct;
    QAction *zoomInAct;
    QAction *zoomOutAct;
    QAction *drawAct;

    QGraphicsScene *scene;
    QGraphicsItem *item;

};
#endif // MAINWINDOW_H

mainwindow.cpp:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "graphicsview.h"

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

    createActions();
    createMenus();

    scene = new QGraphicsScene();
    ui->graphicsView->setScene(scene);

}

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

void MainWindow::createActions()
{
    openAct = new QAction(tr("&Open..."), this);
    openAct->setShortcuts(QKeySequence::Open);
    connect(openAct, SIGNAL(triggered()), this, SLOT(openPhoto()));

    exitAct = new QAction(tr("&Exit"), this);
    exitAct->setShortcuts(QKeySequence::Quit);
    connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));
    
    drawAct = new QAction (tr("&Draw"), this);
}

void MainWindow::createMenus()
{

}

void MainWindow::openPhoto()
{
    QString fileName;
    fileName = QFileDialog::getOpenFileName(this, tr("Open File"), QDir::currentPath());
    QImage image(fileName);
    item = new QGraphicsPixmapItem(QPixmap::fromImage(image));
    scene->addItem(item);
}

void MainWindow::on_pushButton_clicked()
{
    openPhoto();
}

graphicsview.h:

#ifndef GRAPHICSVIEW_H
#define GRAPHICSVIEW_H

#include <QWidget>
#include <QGraphicsView>
#include <QWheelEvent>
#include <QDebug>

class graphicsView : public QGraphicsView
{
    Q_OBJECT
public:
    explicit graphicsView(QWidget *parent = nullptr);
protected:
    virtual void wheelEvent(QWheelEvent *event) override;
    void mousePressEvent(QMouseEvent *event) override;

signals:

public slots:

private:
};

#endif // GRAPHICSVIEW_H

graphicsview.cpp:

#include "graphicsview.h"

graphicsView::graphicsView(QWidget *parent) : QGraphicsView(parent)
{

}

void graphicsView::wheelEvent(QWheelEvent *event)
{
    setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
    double scaleFactor = 1.2;

    if(event->delta() > 0)
    {
        scale(scaleFactor, scaleFactor);
    }
    else
    {
        scale(1/scaleFactor, 1/scaleFactor);
    }
}

void graphicsView::mousePressEvent(QMouseEvent *event)
{
    if(event->button() == Qt::LeftButton)
    {
        qDebug() << "button was pressed";

    }
}

hobbyProgrammer

@jsulm I just update my code, but maybe you have an answer to my next question. How can I check in the mainwindow.cpp the position of the mousepressevent from the graphicsview and if it was a left or right button. I would like to get an immediate signal when the mouse was pressed.

jsulm

@hobbyProgrammer https://doc.qt.io/qt-5/qgraphicsview.html#mousePressEvent