Inherit QListView

GuYan

I want to inherit the QListView class and reimplement the paintEvent function.

class boardView : public QListView
{
Q_OBJECT
public:
boardView(QWidget *parent = nullptr);
protected:
void paintEvent(QPaintEvent *e);
};

But when I want to creat a boardView, it just can't work.

boardView *boardView1 =new boardView(this);
boardView1->setObjectName(QString::fromUtf8("boardView"));
boardView1->setGeometry(QRect(145, 10, 250, 200));

So I created a QListView pointer and changed it into boardView type.

boardView *boardView1 =(boardView *)new boardView(this);

Then it showed in my widget. I really want to know why...

GuYan

@jsulm
“this” is the pointer of the mainwindow.
I have tried to use layout and it finally successed. Thanks a lot!

dheerendra

It cannot work means what is happening ? Why do you want to inherit QListView ? What are you trying to change ?

GuYan

This post is deleted!

GuYan

@dheerendra
I want to reimplement the paintEvent function and paint a background shape for the list, so I inherit QListView. But there 's no view in the wedget when I run the project.
And even if I changed the pointer's type and the view showed, the paintEvent function didn't triggered...So I wonder how can I solve this problem...

dheerendra

Can you try using the Stylesheet for setting the background color ?

GuYan

@dheerendra
Actually I want to not only change the background color but also draw some lines and points on it so Stylesheet can't meet my equirements.

J.Hilk

@GuYan do you call the base class constructor inside your cpp file?

jsulm

@GuYan Please add "override" keyword to paintEvent:

class boardView : public QListView
{
Q_OBJECT
public:
boardView(QWidget *parent = nullptr);
protected:
void paintEvent(QPaintEvent *e) override;
};

And please show the content of your paintEvent implementation.
Did you actually call show() on boardView?

GuYan

@J.Hilk
Yes, I call the boardView class constructor in the mainwindow class constructor... Is there any problem? Because when I create a QListView in the same way, it can show on the mainwindow.

J.Hilk

@GuYan

works perfectly fine for me

#ifndef MYLISTVIEW_H
#define MYLISTVIEW_H

#include <QListView>
#include <QDebug>

class myListView : public QListView
{
    Q_OBJECT

public:
    explicit myListView(QWidget *parent = nullptr) : QListView(parent){}

protected:
    virtual void paintEvent(QPaintEvent *)override{
        qDebug() <<Q_FUNC_INFO;
    }
};

#endif // MYLISTVIEW_H

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    myListView mlw;
    mlw.show();


    return a.exec();
}

GuYan

@jsulm
I have added override keyword now but nothing changed.
If I call the show() function, the view will show on another window, but actually I want it to show in the mainwindow.
The painEvent function is：
void boardView::paintEvent(QPaintEvent *e)
{
QPainter painter(this->viewport());
painter.save();

float W = this -> width(); 
float H = this -> height();

QPoint LeftTopPoint, RightBottomPoint;
LeftTopPoint = QPoint((W - H * 7 / 8) / 2, (H - H * 7 / 8) / 2);
RightBottomPoint = QPoint((W - H * 7 / 8) / 2 + H * 7 / 8, (H - H * 7 / 8) / 2 + H * 7 / 8); 

QRect rect(LeftTopPoint, RightBottomPoint);

QVector<QLine> Lines;
for(int i = 1; i < 14; i++)
{
    Lines.append(QLine(rect.topLeft().x() + rect.width() / 14.0f * i, rect.topLeft().y(), \
                       rect.bottomLeft().x() + rect.width() / 14.0f * i,  rect.bottomLeft().y())); 
    Lines.append(QLine(rect.topLeft().x(), rect.topLeft().y() + rect.height() / 14.0f * i, \
                       rect.topRight().x(),  rect.topRight().y() + rect.height() / 14.0f * i));
}

painter.drawRect(rect); 
painter.drawLines(Lines); 

painter.restore();

}

//your code here

jsulm

@GuYan What is "this" in this line

boardView *boardView1 =new boardView(this);

?
If you want your widget to be shown in your main window you need to add it to the central widget of the main window. See https://stackoverflow.com/questions/9290767/adding-child-in-qmainwindow

GuYan

@jsulm
“this” is the pointer of the mainwindow.
I have tried to use layout and it finally successed. Thanks a lot!