How to create any number of QGraphicsView Dynamically

[R_Irudezu]

I want to create QGraphicsView with QGraphicsScene when button clicked. It's gonna be shown for 5 second and then be deleted. Everytime i pressed the button, the new QGraphicViews need to be created at random locations of UI. How can i achieve this?

[dheerendra]

show the code please.

[R_Irudezu]

@dheerendra
widget.h:

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QGraphicsItem>
#include <QGraphicsView>

namespace Ui {
class Widget;
}

class Widget : public QWidget
{
    Q_OBJECT


public:
    explicit Widget(QWidget *parent = nullptr);
    ~Widget();

    QGraphicsScene *scene;
    QTimeLine *timeline;
    QGraphicsView *gw;
    QGraphicsView *newGw;

    void drawNewGraphicsView
    (
        QGraphicsView *gw_func,
        uint16_t fixedHeight,
        uint16_t fixedWidth,
        uint16_t moveX,
        uint16_t moveY,
        uint16_t lifeTime
    );

private slots:
    void on_pushButton_clicked();

private:
    Ui::Widget *ui;
};

#endif // WIDGET_H

widget.cpp:

#include "widget.h"
#include "ui_widget.h"
#include <QTimeLine>

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

    timeline = new QTimeLine;
    gw = new QGraphicsView(ui->widget);
    drawNewGraphicsView(gw, 80, 80, 150, 150, 3);
}

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

void Widget::drawNewGraphicsView
(
    QGraphicsView *gw_func,
    uint16_t fixedHeight,
    uint16_t fixedWidth,
    uint16_t moveX,
    uint16_t moveY,
    uint16_t lifeTime
)
{
    timeline->setDuration (1000);
    timeline->setCurveShape (QTimeLine::CosineCurve);
    QObject::connect (timeline, SIGNAL(finished()), timeline, SLOT(deleteLater()));

    scene = new QGraphicsScene(this);

    newGw = gw_func;
    newGw->setScene(scene);
    newGw->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    newGw->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff );
    newGw->setStyleSheet("background-color: transparent; border: none;");
    newGw->setFixedHeight(fixedHeight);
    newGw->setFixedWidth(fixedWidth);
    newGw->move(moveX,moveY);
    newGw->setDisabled(true); //scrolling inactivate
    newGw->raise();
    newGw->show();

    scene->setSceneRect (-75, -75, 150, 150);
    setupRot (timeline, scene->addEllipse (rect(35), QPen (QBrush (QColor (0, 153, 255)), 2.4, Qt::DotLine)));
    timeline->setLoopCount (0); 
    timeline->start();
}

void Widget::on_pushButton_clicked()
{
    // adding new graphicview objects to randomly locations
    // lifetime 5 second and want to delete it
}

I couldn't do what i want. I'm gonna create them many, at least mean 3 graphicsView in one second, so i do now want to do memory leak.

[dheerendra]

I did not understand your response. Do you have issue still or not ?

[R_Irudezu]

@dheerendra Sir the issue is that graphicsView objects defined in header are in specific number. I do not want to declare them before compile, i want to create graphicsView objects at runtime:

you can see in the media, i created 3 graphicsView objects, second and third one is creating like that:

void Widget::on_pushButton_clicked()
{
    uint16_t x = (qrand() % 50)*3 ; qDebug() << x;
    uint16_t y = (qrand() % 35)*3 ; qDebug() << x;

    gw1 = new QGraphicsView(ui->widget);
    drawNewGraphicsView(gw1, 120, 120, x, x*2, 5);

    gw2 = new QGraphicsView(ui->widget);
    drawNewGraphicsView(gw2, 130, 160, y, y*2+5, 8);
}

void Widget::on_pushButton_2_clicked()
{
    delete gw1;
    delete gw2;
}

Like i said and like you see, these number of objects are specific, i do not want to specify number of its, what i want is creating how much i want to create of this objects at a (x)second, show them and delete them. Can you help me about that point?

[dheerendra]

How do you get the input on how many number of objects to create ? Is it based on some input ? How do you decide the number of GraphicsView object ?

[R_Irudezu]

@dheerendra it is exactly based on some outputs that an external library callback function gives me. I mean i got 3 * (x,y,w,h)
locations at one second and i have to show this graphic object (the blue cycle in the GIF ) at these locations.

[dheerendra]

when the callback happens store that value in some member variable. Use that member variable to decide on how many Views you need to create.

QGraphicsView **views; // Declare this as member variable in your class.

views = new QGraphicsView* [count]
for(int i=0; i<count;i++ {
    views[i] = new QGraphicsView(ui->widget);
    drawNewGraphicsView(views[i], 130, 160, y, y*2+5, 8);
}

[Asperamanca]

You could simply connect the finished() signal of your timeline to the deleteLater() slots of the QGraphicsScene and QGraphicsView. That way, they are automatically deleted when the timeline expires.

EDIT: No need to keep a pointer to those scenes, unless you need to access them at a later time in your code.

[R_Irudezu]

@Asperamanca It's seems logical about deleting objects after shown but is it possible to define a connect that valid for every QGraphicView object created?

[R_Irudezu]

So i wrote a sample based on @dheerendra and @Asperamanca 's replies.

    //in the header file defined 
    QGraphicsView **views;
    QTimeLine **timelineSet;

    // connect both view and scene objects' deleteLater slots to 
    // timeline's finished signal
    QGraphicsView::connect(timeline, SIGNAL(finished()), newGw, SLOT(deleteLater()));
    QGraphicsScene::connect(timeline, SIGNAL(finished()), scene, SLOT(deleteLater()));

    // in the callback
    views = new QGraphicsView* [5]; //specific 
    for(int i=0; i<5;i++)
    {
        y += 25 + i*12;
        views[i] = new QGraphicsView(ui->widget);
        timelineSet[i] = new QTimeLine();
        drawNewGraphicsView(views[i], 130, 160, y*2+5,  y*2+25, timelineSet[i], lifeT*i%3, 5);
    }

So it's okay now, just like i want. I'm creating objects, showing them for a couple of seconds and delete them automatically with deleteLater().

Thanks for any help :)