how to use scene object of main file in other file? - c++

Question

I tried to make tictactoe game using Qt and Qgraphicsview but when I draw x on board using Graphicstextitem in mousePressEvent , X does not appear. how fix that ?
I think the problem is that scene of textitem Different from scene of main file but I do not know how fix that.
main.cpp:
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Game *gm = new Game;
Game *rect1=new Game;
gm->scenc->setSceneRect(0,0,800,600);
rect1->setRect(160,100,150,150);
gm->scenc->addItem(rect1);
gm->view->setScene(gm->scenc);
gm->view->show();
return a.exec();
}
in game.cpp:
#include <game.h>
Game::Game()
{
scenc= new QGraphicsScene;
view = new QGraphicsView;
text= new QGraphicsTextItem;
}
void Game::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
if (event->buttons() == Qt::LeftButton )
{
text->setPlainText("X");
text->setFont(QFont("Tahoma",24));
text->setPos((160+160+120)/2,140);
scenc->addItem(text);
}
}
in game.h :
class Game : public QObject , public QGraphicsRectItem
{
Q_OBJECT
public:
Game();
QGraphicsScene *scenc;
QGraphicsView *view;
QGraphicsTextItem *text;
void mousePressEvent(QGraphicsSceneMouseEvent *event);
};

Answer 1

The following example illustrates how to do it the right way. Firstly, you have to notice, that Game::mousePressEvent doesn't override any virtual function. It's a good habit to use the override keyword and to drop the virtual keyword in order to be sure, that a virtual function is overwritten.
Game is not derived from QGraphicsScene and has therefore no mousePressEvent member.
Try the following example app.
MyScene.h
#pragma once
#include <QWidget>
#include <QDebug>
#include <QHBoxLayout>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QGraphicsTextItem>
#include <QGraphicsSceneMouseEvent>
class MyScene : public QGraphicsScene {
Q_OBJECT
public:
MyScene(QWidget* parent = nullptr) : QGraphicsScene(parent) {
setSceneRect(0, 0, 800, 600);
}
void mouseDoubleClickEvent(QGraphicsSceneMouseEvent* mouseEvent) override {
if (mouseEvent->buttons() == Qt::LeftButton)
{
auto text = new QGraphicsTextItem;
addItem(text);
text->setPlainText("X");
text->setPos(mouseEvent->scenePos());
}
}
private:
QGraphicsView* mView;
QGraphicsTextItem* mText;
};
main.cpp
#include <QApplication>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QGraphicsTextItem>
#include "MyScene.h"
int main(int argc, char* argv[])
{
QApplication a(argc, argv);
auto scene = new MyScene;
auto view = new QGraphicsView;
view->setScene(scene);
view->show();
return a.exec();
}