How can I re-size the graphicviewitem using mouse

Question

cordsac23. Oktober 2017 13:18

How can I re-size the graphicviewitem using mouse

How can I change the QGraphicView Item size using mouse.In this tutorial have that function to change the size using mouse,but I'm not understand that.Can you explain how resize the rectangle size using mouse.this code generate the 2 rectangles,how can I change the sizes of those rectangles.I also have a question how line item create,resize,move and rotate in this tutorial .

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    scene = new QGraphicsScene();
    ui->graphicsView->setScene(scene);
    scene->setSceneRect(0,0,400,400);
 
    // Create the first red rectangle on the graphic scene
    QGraphicsRectItem *rect1 = new QGraphicsRectItem();
    rect1->setRect(10,50,100,50);
    rect1->setBrush(QBrush(Qt::red));
    rect1->setPen(QPen(QBrush(Qt::black),2));
    scene->addItem(rect1);
 
    // And create a second blue rectangle on the graphic scene
    QGraphicsRectItem *rect2 = new QGraphicsRectItem();
    rect2->setRect(150,100,115,75);
    rect2->setBrush(QBrush(Qt::blue));
    rect2->setPen(QPen(QBrush(Qt::black),2));
    scene->addItem(rect2);
}

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24. Oktober 2017 02:35
(bearbeitet)

First, You need inherit from QGraphicsRectItem and override methods mousePressEvent(), mouseMoveEvent(), mouseReleaseEvent().

You need to understand, how Qt works, and how to work with QGraphicsRectItem, QGraphicsView, QGraphicsScene.

I don`t see reasons to write full code for you. Therefore I will explain main moments and will give you direction to learning.

You can learn inhertence from QGraphicsItem in this article .

Just make moving of QGraphicsItem without Flag ItemIsMovable. Try to do it.
After that, you can make field in QGraphicsItem for resizing.

c

cordsac → Evgenii Legotckoi
#

25. Oktober 2017 16:34

sir,can you explain how this this line item generate when button click and,how rotate,move and resize it using mouse.which classes are related to line functions. I create and re-size the rectangles in this way(I uploaded my sample project here) , now I need to generate line Item when button click and,need to resize,move and rotate like your tutorial.please check my sample project and if you can please edit and give me a solution please.

Thank you!!!

Evgenii Legotckoi → cordsac
#

28. Oktober 2017 07:14

For Line You need create another class which will be inherited from QGraphicsPathItem. And I think, You should use special enum for types of Line or Rectangle.

When You click btn Rectangle or Line, You will set variable, which contains type of current item, with which You work now.
When You work with some item, You need to store pointer to this Item, now You use rect.

But You can you pointer to base class QGraphicsItem for Line or Rectangle. Is it possible.

In my project in article Yu can see variable currentItem .

First, try to make using pointer to base class for Lines and Rectangles.

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