Qt 5.9 | Qt Widgets | C++ Classes | QDoubleSpinBox

Qt 5.9.9 Reference Documentation

# QDoubleSpinBox Class

The QDoubleSpinBox class provides a spin box widget that takes doubles. More...

Header: | #include <QDoubleSpinBox>
qmake: | QT += widgets
Inherits: | QAbstractSpinBox

- List of all members, including inherited members

## Properties

- cleanText : const QString
- decimals : int
- maximum : double
- minimum : double

- prefix : QString
- singleStep : double
- suffix : QString
- value : double

- 12 properties inherited from QAbstractSpinBox
- 59 properties inherited from QWidget

## Public Functions

| QDoubleSpinBox(QWidget *parent = Q_NULLPTR)
| ~QDoubleSpinBox()
QString | cleanText() const
int | decimals() const
double | maximum() const
double | minimum() const
QString | prefix() const
void | setDecimals(int prec)
void | setMaximum(double max)
void | setMinimum(double min)
void | setPrefix(const QString &prefix)
void | setRange(double minimum, double maximum)
void | setSingleStep(double val)
void | setSuffix(const QString &suffix)
double | singleStep() const
QString | suffix() const
virtual QString | textFromValue(double value) const
double | value() const
virtual double | valueFromText(const QString &text) const

## Reimplemented Public Functions

virtual void | fixup(QString &input) const override
virtual QValidator::State | validate(QString &text, int &pos) const override

- 30 public functions inherited from QAbstractSpinBox
- 214 public functions inherited from QWidget

## Public Slots

void | setValue(double val)

- 4 public slots inherited from QAbstractSpinBox
- 19 public slots inherited from QWidget

## Signals

void | valueChanged(double d)
void | valueChanged(const QString &text)

- 1 signal inherited from QAbstractSpinBox
- 3 signals inherited from QWidget

### Additional Inherited Members

- 5 static public members inherited from QWidget
- 20 protected functions inherited from QAbstractSpinBox
- 35 protected functions inherited from QWidget
- 1 protected slot inherited from QWidget

## Detailed Description

The QDoubleSpinBox class provides a spin box widget that takes doubles.

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

Every time the value changes QDoubleSpinBox emits two valueChanged() signals, one taking providing a double 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().

Note: QDoubleSpinBox will round numbers so they can be displayed with the current precision. In a QDoubleSpinBox with decimals set to 2, calling setValue(2.555) will cause value() to return 2.56.

Clicking the up and 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 behavior 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(). The spinbox has a default precision of 2 decimal places but this can be changed using setDecimals().

Most spin boxes are directional, but QDoubleSpinBox can also operate as a circular spin box, i.e. if the range is 0.0-99.9 and the current value is 99.9, 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 QDoubleSpinBox.

Note: The displayed value of the QDoubleSpinBox is limited to 18 characters in addition to eventual prefix and suffix content. This limitation is used to keep the double spin box usable even with extremely large values.

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

### decimals : int

This property holds the precision of the spin box, in decimals

Sets how many decimals the spinbox will use for displaying and interpreting doubles.

Warning: The maximum value for decimals is DBL_MAX_10_EXP + DBL_DIG (ie. 323) because of the limitations of the double type.

Note: The maximum, minimum and value might change as a result of changing this property.

Access functions:

int | decimals() const
void | setDecimals(int prec)

### maximum : double

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 99.99.

Note: The maximum value will be rounded to match the decimals property.

Access functions:

double | maximum() const
void | setMaximum(double max)

See also decimals and setRange().

### minimum : double

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 0.0.

Note: The minimum value will be rounded to match the decimals property.

Access functions:

double | minimum() const
void | setMinimum(double min)

See also decimals, 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:

      spinbox->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 : double

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 1.0. Setting a singleStep value of less than 0 does nothing.

Access functions:

double | singleStep() const
void | setSingleStep(double 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:

      spinbox->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 : double

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.

Note: The value will be rounded so it can be displayed with the current setting of decimals.

Access functions:

double | value() const
void | setValue(double val)

Notifier signal:

void | valueChanged(double d)
void | valueChanged(const QString &text)

See also decimals.

## Member Function Documentation

### QDoubleSpinBox::QDoubleSpinBox(QWidget *parent = Q_NULLPTR)

Constructs a spin box with 0.0 as minimum value and 99.99 as maximum value, a step value of 1.0 and a precision of 2 decimal places. The value is initially set to 0.00. The spin box has the given parent.

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

### QDoubleSpinBox::~QDoubleSpinBox()

Destructor.

### `[override virtual]` void QDoubleSpinBox::fixup(QString &input) const

Reimplemented from QAbstractSpinBox::fixup().

### void QDoubleSpinBox::setRange(double minimum, double maximum)

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

Note: The maximum and minimum values will be rounded to match the decimals property.

      setRange(minimum, maximum);

is equivalent to:

      setMinimum(minimum);
      setMaximum(maximum);

See also minimum and maximum.

### `[virtual]` QString QDoubleSpinBox::textFromValue(double 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 using QWidget::locale().toString(value, QLatin1Char('f'), decimals()) and will remove the thousand separator unless setGroupSeparatorShown() is set. Reimplementations may return anything.

Note: QDoubleSpinBox 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().

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

### `[override virtual]` QValidator::State QDoubleSpinBox::validate(QString &text, int &pos) const

Reimplemented from QAbstractSpinBox::validate().

### `[signal]` void QDoubleSpinBox::valueChanged(double d)

This signal is emitted whenever the spin box's value is changed. The new value is passed in d.

Note: Signal valueChanged is overloaded in this class. To connect to this one using the function pointer syntax, you must specify the signal type in a static cast, as shown in this example:

      connect(doubleSpinBox, static_cast<void(QDoubleSpinBox::*)(double)>(&QDoubleSpinBox::valueChanged),
          [=](double d){ /* ... */ });

Note: Notifier signal for property value.

### `[signal]` void QDoubleSpinBox::valueChanged(const QString &text)

This is an overloaded function.

The new value is passed in text with prefix() and suffix().

Note: Signal valueChanged is overloaded in this class. To connect to this one using the function pointer syntax, you must specify the signal type in a static cast, as shown in this example:

      connect(doubleSpinBox, static_cast<void(QDoubleSpinBox::*)(const QString &)>(&QDoubleSpinBox::valueChanged),
          [=](const QString &text){ /* ... */ });

Note: Notifier signal for property value.

### `[virtual]` double QDoubleSpinBox::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: QDoubleSpinBox handles specialValueText() separately; this function is only concerned with the other values.

See also textFromValue() and validate().