Select items in a Scene when I press a button.

AlvaroS

Hi there!!

I have a scene with items. I would like to do that when user press a button, all the item can be selectable and then the users can select the item that they want.

how can I do that? Which class should I use?
Thanks a lot.

mrjj

hi
Have you seen the
http://doc.qt.io/qt-5/qtwidgets-graphicsview-diagramscene-example.html
it can select an item and delete etc.

You might need to set
item->setFlag(QGraphicsItem::ItemIsSelectable, true);
on your items.

AlvaroS

@mrjj First of all thanks for answering.
The problem is that I do not understand the way that users can select items.

mrjj

@AlvaroS
hi
Well the framework can do it for you if you tell it its ok with
youritem->setFlag(QGraphicsItem::ItemIsSelectable, true);

Then user can just click on it.
The default is no flag so you need this i think.

AlvaroS

@mrjj thanks again my friend.

This is my code where I construc the scene:

    QGraphicsLineItem *line;
    QGraphicsScene *scene;

for (int i=0;i<num_lines;i++)
                {
                    words = lines.at(i).split(" ", QString::SkipEmptyParts); // Split each line in words
                    lines_struct[i].x_start= words.at(0).toDouble(); //We take the first word and convert it to Double because it was QString type before
                    lines_struct[i].y_start= words.at(1).toDouble(); //Second word
                    lines_struct[i].x_end= words.at(2).toDouble(); //Third word
                    lines_struct[i].y_end= words.at(3).toDouble(); //Fourth word

                    QPen blue(Qt::blue); //Draw lines in blue
                    blue.setWidth(0.7); //Lines width
                    line = scene->addLine((lines_struct[i].x_start),(lines_struct[i].y_start),(lines_struct[i].x_end),(lines_struct[i].y_end), blue);         
                }
                    /*
                     * Adjust scene (map) to graphicsview
                     */
                   ui->graphicsView->scale(ui->graphicsView->width()/scene->width(),ui->graphicsView->height()/scene->height()); // Adjust map to the graphicsView using a scale
                   qreal x, y;
                   x=ui->graphicsView->width()/scene->width(); // Get scale X
                   y=ui->graphicsView->height()/scene->width(); // Get Scale Y
                   // line->setFlag(QGraphicsItem::ItemIsSelectable);
                   // line->setFlag(QGraphicsItem::ItemIsMovable);
                   ui->graphicsView->setFixedSize(10+(x*scene->width()),10+(y*scene->height())); //We fit the size of graphicsView just adding pixel to fitting well
        }
}
}

void MainWindow::on_Select_items_clicked()
{
    line->setFlag(QGraphicsItem::ItemIsSelectable, true);
}

When User click on Select_items I want that they can select items that they want.
But it does not work. (Qt does not give me errors)

mrjj

@AlvaroS said:
Hi
You need to set it on all items
...
line = scene->addLine(xxx....
line->setFlag(QGraphicsItem::ItemIsSelectable, true); // set for all 10
}
not later :)

Did u try the Diagram sample ?
Its available directly to run.

AlvaroS

@mrjj Thanks a lot.
That is work!
How can I do to when the user is on item the mouse show a hand instead of a tipical arrow??

Thanks again!!

mrjj

hi
ui->widget->setCursor(Qt::OpenHandCursor);
Might need other hand. :)

And this to restore the cursor back to normal
ui->widget->setCursor(Qt::ArrowCursor);

AlvaroS

@mrjj Thanks a lot. It works fine for me but I have a problem.
First a put the code that it works fine because maybe it helps to someone:

                    //QGraphicsLineItem line_scene[i] = line;
                    line->setFlag(QGraphicsItem::ItemIsSelectable, true); // Every items can be selected
                    line->setFlag(QGraphicsItem::ItemIsMovable, true);    //Every items can be movabled
                    line->setCursor(Qt::PointingHandCursor); // When the cursor is on a line item it change to a hand cursor instead of a tipical arrow.

Now I have a problem because the line items are too narrow and it is dificult to select them.

I did this:

//To draw items

                QPen blue(Qt::blue); //Draw lines in blue
                blue.setWidth(0); //Lines width

                line = scene->addLine(( ........... , blue);


//To fit scene to the graphicsView:

ui->graphicsView->scale(ui->graphicsView->width()/scene->width(),ui->graphicsView->height()/scene->height()); // Adjust map to the graphicsView using a scale
                   qreal x, y;
                   x=ui->graphicsView->width()/scene->width(); // Get scale X
                   y=ui->graphicsView->height()/scene->width(); // Get Scale Y
                   ui->graphicsView->setFixedSize(5+(x*scene->width()),5+(y*scene->height())); //We fit the size of graphicsView just adding pixel to fitting well

The problem is that when I write more than 0 in blue.widht, the line items are really thick and I think that it is because it scale the width as well in ui->graphicsView->scale.....

How can I solved that?

Thanks a lot!

mrjj

hi
When you set a pen's width it will scale with there view
you can try
blue.setCosmetic(true);