CODEWITHSUNDEEP
c++qt
JokerMartini
JokerMartini

Reputation: 6147

How to access widgets in a subclass?

I have created a subclass of QLineEdit and I am adding a button to the right side of the widget, so I can make an all-in-one path browsing control. However, I need to access the button from within the resizeEvent, so I can properly place the button on the right side of the line edit. I get errors and I am assuming it is due to the way I have created the button.

enter image description here

lineeditpath.h

#ifndef LINEEDITPATH_H
#define LINEEDITPATH_H

#include <QLineEdit>
#include <QFileDialog>
#include <QPushButton>

class LineEditPath : public QLineEdit
{
    Q_OBJECT
public:
    explicit LineEditPath(QWidget *parent = 0);

signals:

public slots:

protected:
    void resizeEvent(QResizeEvent *event) override;

private:
    QFileDialog *dialog;
    QPushButton *button;
};

#endif // LINEEDITPATH_H

lineedithpath.cpp

#include "lineeditpath.h"
#include <QLineEdit>
#include <QPushButton>

LineEditPath::LineEditPath(QWidget *parent) : QLineEdit(parent) {
    setAcceptDrops(true);

    auto button = new QPushButton("...", this);
    button->setFixedWidth(30);
    button->setCursor(Qt::CursorShape::PointingHandCursor);
    button->setFocusPolicy(Qt::FocusPolicy::NoFocus);
    setTextMargins(0,0,30,0); }

void LineEditPath::resizeEvent(QResizeEvent *event) {
    QLineEdit::resizeEvent(event);

    // Resize the button: ERROR
    button->move(width()-button->sizeHint().width(), 0);

}

error:

---------------------------
Signal Received
---------------------------
<p>The inferior stopped because it received a signal from the operating system.<p><table><tr><td>Signal name : </td><td>SIGSEGV</td></tr><tr><td>Signal meaning : </td><td>Segmentation fault</td></tr></table>
---------------------------
OK   
---------------------------

Upvotes: 1

Views: 91

Answers (1)

Jesper Juhl
Jesper Juhl

Reputation: 31468

auto button = new QPushButton("...", this); in your constructor does not initialize the button member variable of your class. It creates a new local variable with the same name that shadows the member variable and goes out of scope at the end of the constructor body. Your member variable is never initialized.

You want button = new QPushButton("...", this); - or even better; move that to your constructors initialization list rather than using the ctor body.

Using the initialization list:

LineEditPath::LineEditPath(QWidget *parent) :
    QLineEdit(parent), 
    button(new QPushButton("...", this)) 
{

You also never initialize your dialog member variable.

Upvotes: 2

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