QDoubleSpinBox with leading zeros (always 4 digits)

Question

I have a QDoubleSpinBox in the range of 0-7000, but I want the value to always be displayed as 4 digits (0-> 0000, 1 → 0001, 30 → 0030, 3333 → 3333).

I understand that I can add prefix , but the prefix is ​​always added. What are my options?

Answer 1

If you use integers, then a QSpinBox will suffice.

You can simply inherit from QSpinBox and reimplement the textFromValue function:

 class MySpinBox: public QSpinBox { Q_OBJECT public: MySpinBox( QWidget * parent = 0) : QSpinBox(parent) { } virtual QString textFromValue ( int value ) const { /* 4 - number of digits, 10 - base of number, '0' - pad character*/ return QString("%1").arg(value, 4 , 10, QChar('0')); } }; 

Filling a QString in this way does the trick.

Answer 2

Since prefix not a solution, if you consider negative values, then, in my opinion, the best and most elegant solution is to define your own custom spin box by getting a QAbstractSpinBox . Here is a small example:

Note that it is far from perfect and serves as an example of what can be done:

q4digitspinbox.h:

 #ifndef Q4DIGITSPINBOX_H #define Q4DIGITSPINBOX_H #include <QAbstractSpinBox> #include <QLineEdit> class Q4DigitSpinBox : public QAbstractSpinBox { Q_OBJECT public: explicit Q4DigitSpinBox(QWidget *parent = 0); StepEnabled stepEnabled() const; double maximum() const; double minimum() const; void setMaximum(double max); void setMinimum(double min); void setRange(double minimum, double maximum); double value() const; public slots: virtual void stepBy(int steps); void setValue(double val); signals: void valueChanged(double i); void valueChanged(const QString & text); private: double m_value; double m_minimum; double m_maximum; QLineEdit m_lineEdit; }; #endif // Q4DIGITSPINBOX_H 

q4digitspinbox.h:

 #include "q4digitspinbox.h" Q4DigitSpinBox::Q4DigitSpinBox(QWidget *parent) : QAbstractSpinBox(parent), m_value(0), m_minimum(-99), m_maximum(99) { setLineEdit(&m_lineEdit); setValue(0.0); } QAbstractSpinBox::StepEnabled Q4DigitSpinBox::stepEnabled() const { return StepUpEnabled | StepDownEnabled; } double Q4DigitSpinBox::maximum() const { return m_maximum; } double Q4DigitSpinBox::minimum() const { return m_minimum; } void Q4DigitSpinBox::setMaximum(double max) { m_maximum = max; } void Q4DigitSpinBox::setMinimum(double min) { m_minimum = min; } void Q4DigitSpinBox::setRange(double minimum, double maximum) { m_minimum = minimum; m_maximum = maximum; } double Q4DigitSpinBox::value() const { return m_value; } void Q4DigitSpinBox::stepBy(int steps) { m_value += (double)steps / 10; if (fabs(m_value - 0) < 0.00001) { m_value = 0; } if(m_value < m_minimum || m_value > m_maximum) { return; } int prefixNumberOfDigits = 4; QString valueAsString = QString("%1").arg((int)m_value); int numberOfDigits = valueAsString.length(); QString prefix; prefixNumberOfDigits -= numberOfDigits; if(prefixNumberOfDigits > 0) { while(prefixNumberOfDigits--) { prefix += "0"; } } QString value; if(m_value < 0) { value = QString("-%1%2").arg(prefix).arg(-m_value); } else { value = QString("%1%2").arg(prefix).arg(m_value); } m_lineEdit.setText(value); emit valueChanged(m_value); emit valueChanged(value); } void Q4DigitSpinBox::setValue(double val) { if(val < m_minimum || val > m_maximum) { return; } int prefixNumberOfDigits = 4; QString valueAsString = QString("%1").arg((int)val); int numberOfDigits = valueAsString.length(); QString prefix; prefixNumberOfDigits -= numberOfDigits; if(prefixNumberOfDigits > 0) { while(prefixNumberOfDigits--) { prefix += "0"; } } QString value; if(val < 0) { value = QString("-%1%2").arg(prefix).arg(-val); } else { value = QString("%1%2").arg(prefix).arg(val); } m_lineEdit.setText(value); emit valueChanged(val); emit valueChanged(value); } 

I did not provide comments, since I thought it was pretty straightforward, but if necessary, I can add a few more explanations.

Hope this helps.