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# QDoubleSpinBox Class Reference

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

    #include <QDoubleSpinBox>

Inherits QAbstractSpinBox.

- List of all members, including inherited members

### Writable Properties

maximum : double minimum : double precision : int prefix : QString | singleStep : double specialValueText : QString suffix : QString value : double

- 6 writable properties inherited from QAbstractSpinBox
- 33 writable properties inherited from QWidget
- 1 writable property inherited from QObject

### Read-Only Properties

- 2 read-only properties inherited from QAbstractSpinBox
- 24 read-only properties inherited from QWidget

### Public Functions

- QDoubleSpinBox ( QWidget * parent = 0 )
- virtual double mapTextToValue ( QString * txt, QValidator::State * state ) const
- virtual QString mapValueToText ( double v ) const
- void setRange ( double min, double max )

- 2 public functions inherited from QAbstractSpinBox
- 83 public functions inherited from QWidget
- 24 public functions inherited from QObject
- 2 public functions inherited from QPaintDevice

### Public Slots

- void setValue ( double val )

- 16 public slots inherited from QWidget
- 1 public slot inherited from QObject

### Signals

- void valueChanged ( double d )
- void valueChanged ( QString text )

- 1 signal inherited from QObject

### Static Public Members

- 4 static public members inherited from QWidget
- 4 static public members inherited from QObject

### Protected Functions

- 3 protected functions inherited from QAbstractSpinBox
- 44 protected functions inherited from QWidget
- 9 protected functions inherited from QObject

## 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. If the value is entered directly into the spin box, the value will be changed and valueChanged() will be emitted with the new value when Enter or Return is pressed, when the spin box loses focus or when the spin box is deactivated (see QWidget::windowActivationChanged()). If tracking() is true the value will be changed each time the value is changed in the editor. The spin box supports double values but can be extended to use different strings with mapValueToText() and mapTextToValue().

Every time the value changes QDoubleSpinBox emits the valueChanged() signal. The current value can be fetched with value() and set with setValue().

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 lineStep(). 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 setLineStep(). The spinbox has a default precision of 2 decimal places but this can be changed using setPrecision().

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.

## Property Documentation

### 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.

Access functions:

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

See also 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.

Access functions:

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

See also setRange() and specialValueText.

### precision : int

This property holds the precision of the spin box.

The precision sets how many decimals you want to display when displaying double values. Valid ranges for decimals is 0-14.

Access functions:

- int precision () const
- void setPrecision ( int prec )

### 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 & p )

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 )

See also setSingleStep().

### specialValueText : QString

This property holds the special-value text.

If set, the spin box will display this text instead of a numeric value whenever the current value is equal to minimum(). Typical use is to indicate that this choice has a special (default) meaning.

For example, if your spin box allows the user to choose the margin width in a print dialog and your application is able to automatically choose a good margin width, you can set up the spin box like this:

        QDoubleSpinBox marginBox(-1.0, 20.0, 1.0, 1, parent);
        marginBox.setSuffix(" mm");
        marginBox.setSpecialValueText("Auto");

The user will then be able to choose a margin width from 0.0-20.0 millimeters or select "Auto" to leave it to the application to choose. Your code must then interpret the spin box value of -1 as the user requesting automatic margin width.

All values are displayed with the prefix() and suffix() (if set), except for the special value, which only shows the special value text.

To turn off the special-value text display, call this function with an empty string. The default is no special-value text, i.e. the numeric value is shown as usual.

If no special-value text is set, specialValueText() returns an empty string.

Access functions:

- QString specialValueText () const
- void setSpecialValueText ( const QString & s )

### 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 minValue() if specialValueText() is set.

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

Access functions:

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

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.

Access functions:

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

See also setValue().

## Member Function Documentation

### QDoubleSpinBox::QDoubleSpinBox ( QWidget * parent = 0 )

Constructs a spin box with no minimum and maximum values, 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 minimum(), setMinimum(), maximum(), setMaximum(), lineStep(), and setLineStep().

### double QDoubleSpinBox::mapTextToValue ( QString * txt, QValidator::State * state ) const `[virtual]`

This virtual function is used by the spin box whenever it needs to interpret text entered by the user as a value. Note that neither prefix() nor suffix() are included when this function is called by Qt. If state is not 0 it is set accordingly.

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

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

The default implementation tries to interpret txt as a double using QString::toDouble() For an empty string or "-" (if negative values are allowed in the spinbox) it returns 0.

Warning: This function must not be called with txt == 0.

See also mapValueToText().

### QString QDoubleSpinBox::mapValueToText ( double v ) const `[virtual]`

This virtual function is used by the spin box whenever it needs to display value v. The default implementation returns a string containing v printed using QString::number(v, QLatin1Char('f'), precision()). Reimplementations may return anything.

Note that Qt 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 mapTextToValue().

See also mapTextToValue().

### void QDoubleSpinBox::setRange ( double min, double max )

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

        setRange(min, max);

is equivalent to:

        setMinimum(min);
        setMaximum(max);

See also minimum and maximum.

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

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

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

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

The new value is passed literally in text with no prefix() or suffix().