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QSpinBox Class

The QSpinBox class provides a spin box widget. More...

Header: #include <QSpinBox>
qmake: QT += widgets
Inherits: QAbstractSpinBox.

Properties

Public Functions

QSpinBox(QWidget * parent = 0)
~QSpinBox()
QString cleanText() const
int displayIntegerBase() const
int maximum() const
int minimum() const
QString prefix() const
void setDisplayIntegerBase(int base)
void setMaximum(int max)
void setMinimum(int min)
void setPrefix(const QString & prefix)
void setRange(int minimum, int maximum)
void setSingleStep(int val)
void setSuffix(const QString & suffix)
int singleStep() const
QString suffix() const
int value() const

Public Slots

void setValue(int val)

Signals

void valueChanged(int i)
void valueChanged(const QString & text)

Protected Functions

virtual QString textFromValue(int value) const
virtual int valueFromText(const QString & text) const

Reimplemented Protected Functions

virtual bool event(QEvent * event)
virtual void fixup(QString & input) const
virtual QValidator::State validate(QString & text, int & pos) const

Additional Inherited Members

  • 5 static public members inherited from QWidget
  • 11 static public members inherited from QObject
  • 1 protected slot inherited from QWidget

Detailed Description

The QSpinBox class provides a spin box widget.

QSpinBox is designed to handle integers and discrete sets of values (e.g., month names); use QDoubleSpinBox for floating point values.

QSpinBox allows the user to choose a value by clicking the up/down buttons or pressing up/down on the keyboard to increase/decrease the value currently displayed. The user can also type the value in manually. The spin box supports integer values but can be extended to use different strings with validate(), textFromValue() and valueFromText().

Every time the value changes QSpinBox emits two valueChanged() signals, one providing an int and the other a QString. The QString overload provides the value with both prefix() and suffix(). The current value can be fetched with value() and set with setValue().

Clicking the up/down buttons or using the keyboard accelerator's up and down arrows will increase or decrease the current value in steps of size singleStep(). If you want to change this behaviour you can reimplement the virtual function stepBy(). The minimum and maximum value and the step size can be set using one of the constructors, and can be changed later with setMinimum(), setMaximum() and setSingleStep().

Most spin boxes are directional, but QSpinBox can also operate as a circular spin box, i.e. if the range is 0-99 and the current value is 99, clicking "up" will give 0 if wrapping() is set to true. Use setWrapping() if you want circular behavior.

The displayed value can be prepended and appended with arbitrary strings indicating, for example, currency or the unit of measurement. See setPrefix() and setSuffix(). The text in the spin box is retrieved with text() (which includes any prefix() and suffix()), or with cleanText() (which has no prefix(), no suffix() and no leading or trailing whitespace).

It is often desirable to give the user a special (often default) choice in addition to the range of numeric values. See setSpecialValueText() for how to do this with QSpinBox.

Screenshot of a Windows Vista spin boxA spin box shown in the Windows Vista widget style.
Screenshot of a Fusion spin boxA spin box shown in the Fusion widget style.
Screenshot of a Macintosh spin boxA spin box shown in the Macintosh widget style.

Subclassing QSpinBox

If using prefix(), suffix(), and specialValueText() don't provide enough control, you subclass QSpinBox and reimplement valueFromText() and textFromValue(). For example, here's the code for a custom spin box that allows the user to enter icon sizes (e.g., "32 x 32"):

int IconSizeSpinBox::valueFromText(const QString &text) const
{
    QRegExp regExp(tr("(\\d+)(\\s*[xx]\\s*\\d+)?"));

    if (regExp.exactMatch(text)) {
        return regExp.cap(1).toInt();
    } else {
        return 0;
    }
}

QString IconSizeSpinBox::textFromValue(int value) const
{
    return tr("%1 x %1").arg(value);
}

See the Icons example for the full source code.

See also QDoubleSpinBox, QDateTimeEdit, QSlider, and Spin Boxes Example.

Property Documentation

cleanText : const QString

This property holds the text of the spin box excluding any prefix, suffix, or leading or trailing whitespace.

Access functions:

QString cleanText() const

See also text, QSpinBox::prefix, and QSpinBox::suffix.

displayIntegerBase : int

This property holds the base used to display the value of the spin box.

The default displayIntegerBase value is 10.

This property was introduced in Qt 5.2.

Access functions:

int displayIntegerBase() const
void setDisplayIntegerBase(int base)

See also textFromValue() and valueFromText().

maximum : int

This property holds the maximum value of the spin box.

When setting this property the minimum is adjusted if necessary, to ensure that the range remains valid.

The default maximum value is 99.

Access functions:

int maximum() const
void setMaximum(int max)

See also setRange() and specialValueText.

minimum : int

This property holds the minimum value of the spin box.

When setting this property the maximum is adjusted if necessary to ensure that the range remains valid.

The default minimum value is 0.

Access functions:

int minimum() const
void setMinimum(int min)

See also setRange() and specialValueText.

prefix : QString

This property holds the spin box's prefix.

The prefix is prepended to the start of the displayed value. Typical use is to display a unit of measurement or a currency symbol. For example:

sb->setPrefix("$");

To turn off the prefix display, set this property to an empty string. The default is no prefix. The prefix is not displayed when value() == minimum() and specialValueText() is set.

If no prefix is set, prefix() returns an empty string.

Access functions:

QString prefix() const
void setPrefix(const QString & prefix)

See also suffix(), setSuffix(), specialValueText(), and setSpecialValueText().

singleStep : int

This property holds the step value.

When the user uses the arrows to change the spin box's value the value will be incremented/decremented by the amount of the singleStep. The default value is 1. Setting a singleStep value of less than 0 does nothing.

Access functions:

int singleStep() const
void setSingleStep(int val)

suffix : QString

This property holds the suffix of the spin box.

The suffix is appended to the end of the displayed value. Typical use is to display a unit of measurement or a currency symbol. For example:

sb->setSuffix(" km");

To turn off the suffix display, set this property to an empty string. The default is no suffix. The suffix is not displayed for the minimum() if specialValueText() is set.

If no suffix is set, suffix() returns an empty string.

Access functions:

QString suffix() const
void setSuffix(const QString & suffix)

See also prefix(), setPrefix(), specialValueText(), and setSpecialValueText().

value : int

This property holds the value of the spin box.

setValue() will emit valueChanged() if the new value is different from the old one. The value property has a second notifier signal which includes the spin box's prefix and suffix.

Access functions:

int value() const
void setValue(int val)

Notifier signal:

void valueChanged(int i)
void valueChanged(const QString & text)

Member Function Documentation

QSpinBox::​QSpinBox(QWidget * parent = 0)

Constructs a spin box with 0 as minimum value and 99 as maximum value, a step value of 1. The value is initially set to 0. It is parented to parent.

See also setMinimum(), setMaximum(), and setSingleStep().

QSpinBox::​~QSpinBox()

Destructor.

[virtual protected] bool QSpinBox::​event(QEvent * event)

Reimplemented from QObject::event().

[virtual protected] void QSpinBox::​fixup(QString & input) const

Reimplemented from QAbstractSpinBox::fixup().

void QSpinBox::​setRange(int minimum, int maximum)

Convenience function to set the minimum, and maximum values with a single function call.

setRange(minimum, maximum);

is equivalent to:

setMinimum(minimum);
setMaximum(maximum);

See also minimum and maximum.

[virtual protected] QString QSpinBox::​textFromValue(int value) const

This virtual function is used by the spin box whenever it needs to display the given value. The default implementation returns a string containing value printed in the standard way using QWidget::locale().toString(), but with the thousand separator removed unless setGroupSeparatorShown() is set. Reimplementations may return anything. (See the example in the detailed description.)

Note: QSpinBox does not call this function for specialValueText() and that neither prefix() nor suffix() should be included in the return value.

If you reimplement this, you may also need to reimplement valueFromText() and validate()

See also valueFromText(), validate(), and QLocale::groupSeparator().

[virtual protected] QValidator::State QSpinBox::​validate(QString & text, int & pos) const

Reimplemented from QAbstractSpinBox::validate().

[virtual protected] int QSpinBox::​valueFromText(const QString & text) const

This virtual function is used by the spin box whenever it needs to interpret text entered by the user as a value.

Subclasses that need to display spin box values in a non-numeric way need to reimplement this function.

Note: QSpinBox handles specialValueText() separately; this function is only concerned with the other values.

See also textFromValue() and validate().

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