How do I move a QPixMapImage around a qgraphicsview - c++

Question

I can add a QPixMapImage to a QGraphicsScene, but then I have two issues.
First I cannot create a pointer to my QPixmapItem declared in the header, where i can with QGraphicsScene.
I get an error "error: no matching function for call to 'QGraphicsPixmapItem::QGraphicsPixmapItem(MainWindow* const)" ... When I create my QGraphicsScene in Main the same way?
Second issue: I cannot move the QGraphicsPixmapItem around when the slider is moved (obv i won't until the pointer is working). But can I even move it, or do i have to repaint it?
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QtGui>
#include <QGraphicsView>
#include <QGraphicsPixmapItem>
#include <QPixmap>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
scene = new QGraphicsScene(this);
QPixmap arrow = QPixmap::fromImage(QImage("ARROW.png"));
arrowItem = new QGraphicsPixmapItem(this);
arrowItem->setPixmap(arrow);
ui->graphicsView->setScene(scene);
ui->horizontalSlider->setMaximum(2000);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_horizontalSlider_sliderMoved(int position)
{
arrowItem->setPos(position,position);
scene->addItem(arrowItem);
}
Header:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QGraphicsPixmapItem>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private:
Ui::MainWindow *ui;
QGraphicsPixmapItem *arrowItem;
QGraphicsScene *scene;
private slots:
void on_horizontalSlider_sliderMoved(int position);
};
#endif // MAINWINDOW_H

Answer 1

Issue #1:
There error you're getting means there is no such constructor declared for QGraphicsPixmapItem; you use either one of these:
QGraphicsPixmapItem(QGraphicsItem *parent = 0
#ifndef Q_QDOC
// ### obsolete argument
, QGraphicsScene *scene = 0
#endif
);
QGraphicsPixmapItem(const QPixmap &pixmap, QGraphicsItem *parent = 0
#ifndef Q_QDOC
// ### obsolete argument
, QGraphicsScene *scene = 0
#endif
);
Issue#2
If I understood your question correctly you want to be able to drag your graphics items around the scene. You can switch this functionality on by using view->setDragMode method.
Please see if an example below would work for you:
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QGraphicsScene* scene = new QGraphicsScene(QRect(-50, -50, 400, 200));
QPixmap image = QPixmap::fromImage(QImage("image.JPG"));
QGraphicsPixmapItem* pixMapItem = new QGraphicsPixmapItem();
pixMapItem->setPixmap(image);
scene->addItem(pixMapItem);
QGraphicsView* view = new QGraphicsView(ui->centralWidget);
view->setScene(scene);
view->setGeometry(QRect(50, 50, 400, 200));
view->setDragMode(QGraphicsView::ScrollHandDrag);
view->show();
}
hope this helps, regards