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I have a simple QDialog that shows a QLabel in black text. I'd like for the QLabel's text to turn red when I press the a key. I am using the designer to make the dialog. Here is my code:

myDialog.h

#include <QDialog>
#include <QWidget>

namespace Ui {
class myDialog;
}

class myDialog : public QDialog
{
  Q_OBJECT

public:
  explicit myDialog(QWidget* parent = 0);
  ~myDialog();

private:
  Ui::myDialog* ui;

protected:
  void keyPressEvent(QKeyEvent* event);
};

myDialog.cpp

#include "myDialog.h"
#include "ui_myDialog.h"
#include <QKeyEvent>

myDialog::myDialog(QWidget* parent) :
  QDialog(parent),
  ui(new Ui::myDialog)

{
  ui->setupUi(this);
}

void myDialog::eventPressEvent(QKeyEvent* event)
{
  if (event->key()==Qt::Key_A){
    Ui_myDialog::label1->setStyleSheet(QStringLiteral("QLabel{color: rgb(170, 0, 0);}"));
  } else {
    qDebug << "FAIL";
  }
}

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

ui_mydialog.h

/********************************************************************************
** Form generated from reading UI file 'about.ui'
** Created by: Qt User Interface Compiler version 5.5.0
** WARNING! All changes made in this file will be lost when recompiling UI file!
********************************************************************************/

#ifndef UI_MYDIALOG_H
#define UI_MYDIALOG_H

...<snip>...

QT_BEGIN_NAMESPACE

class Ui_myDialog
{
public:
    QLabel *label1;

    void setupUi(QDialog *myDialog)
    {
        ...<snip>...
        label1 = new QLabel(myDialog);
        label1->setObjectName(QStringLiteral("label1"));
        label1->setGeometry(QRect(50, 333, 16, 20));
        label1->setFont(font);
        label1->setAlignment(Qt::AlignCenter);
        ...<snip>...

    } // setupUi

    ...<snip>...  

namespace Ui {
    class myDialog: public Ui_myDialog {};
} // namespace Ui

QT_END_NAMESPACE

#endif // UI_MYDIALOG_H

So, here's the issue. When I build the project, a file called ui_mydialog.h gets created and is generated in the build folder. This file even says it was auto-generated by the Qt User Interface Compiler. When I try to change the stylesheet of label1 (which is declared in ui_mydialog.h) in myDialog.cpp using the line:

Ui_myDialog::label1->setStyleSheet(QStringLiteral("QLabel{color: rgb(170, 0, 0);}"));

...I get an error that says error: invalid use of non-static data member 'Ui_myDialog::label1'. This is where I'm stuck. How would I go about correctly passing label1 into the void myDialog::eventPressEvent(QKeyEvent* event) member function and modifying it?

Any help would be appreciated.

earth
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  • Why do you need the `Ui_myDialog::` part? Just use `label1->setStyleSheet(QStringLiteral("QLabel{color: rgb(170, 0, 0);}"));` – drescherjm Feb 19 '16 at 03:52
  • Yep, tried that and I get an error saying that label1 was not declared in this scope. – earth Feb 19 '16 at 03:55
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    Oh you use your ui different than what I do (composition instead of inheritance). In your case it should be: `ui->label1->setStyleSheet(QStringLiteral("QLabel{color: rgb(170, 0, 0);}"));` – drescherjm Feb 19 '16 at 03:58
  • Ahh, that did it. Could you add that as an answer so I can mark as complete? Thank you! – earth Feb 19 '16 at 04:01

2 Answers2

4

Using Ui_myDialog:: on a non-static member is incorrect.

You need to replace 

Ui_myDialog::label1->setStyleSheet(QStringLiteral("QLabel{color: rgb(170, 0, 0);}"));

with 

ui->label1->setStyleSheet(QStringLiteral("QLabel{color: rgb(170, 0, 0);}"));
drescherjm
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0

You don't need new Ui::myDialog in 'myDialog.cpp'.

1) myDialog.h

Add #include "ui_mydialog.h" Change Ui::myDialog* ui; to Ui::myDialog ui;

2) myDialog.cpp

Remove ui(new Ui::myDialog) in constructor.

And, then you can use ui.label1->......

hyun
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