How to draw dash instead of null in QSpinBox?

Question

I need to draw dash instead of null in QSpinBox. Also I need to make dash key pressing equalling null key pressing.

How can I do this?

Answer 1

You can use setSpecialValueText();

 QSpinBox spinBox;
 spinBox->setSpecialValueText(tr("-"));

You can then check if the special value is selected by connecting valueChanged(QString) function. Note that this is different from valueChanged(int) You can then check the value of the passed string in a slot, and if it is equal to special text, you can do something.

 main()
 {
      connect(spinBox, SIGNAL(valueChanged(QString)), this, SLOT(doSomething(QString)));
 }

 void doSomething(QString valueStr)
 {
     if(valueStr == spinBox->specialValueText())
           // Do something
     else
           //Convert valueStr to int and do other stuff
 }

Or you could do something like this:

 main()
 {
      connect(spinBox, SIGNAL(valueChanged()), this, SLOT(doSomething()));
 }

 void doSomething()
 {
     if(spinBox->value() == 0)
           // Do something with dash
     else
           //Do something with the value
 }

For your other question, you need to create a keyPressEvent and check if pressed key is dash or not. If it's dash you can call another function to do something. Edit: BTW, the index of specialValueText() is 0.

Edit: Or you can create a QShortcut in your main function.

 new QShortcut(QKeySequence(Qt::Key_Minus), this, SLOT(doSomething()));

Edit continued: doSomething() is a slot function. Put, for example void doSomething(); in the private slots: section of your header file. And in the cpp file define a function similar to this:

 void MainWindow::doSomething()
 {
     ui->spinBox->setValue(0);
     //This is the slot called when you press dash.
 }

Edit still continued: You need to declare a protected: function in the header like this:

 virtual void keyPressEvent(QKeyEvent *event);

Then you need to define this function in your cpp file. Like this:

 void MainWindow::keyPressEvent(QKeyEvent *event)
 {
     if(event->key() == Qt::Key_Minus)
         ui->spinBox->setValue(0);
 }

You don't have to connect any signals or slots for this function. It's an event.

That means when dash is pressed ui->spinBox->setValue(0);

Because of that, you need to create a spinBox with a range starting from 0.

 spinBox->setRange(0, 100);

That means,

 if(spinBox->value() == 0)
      //Then specialValueText is selected.