QDoubleSpinBox Class Reference
^{[QtGui module]}

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()). 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 the valueChanged() signal. 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.

See also QSpinBox, QSlider, and GUI Design Handbook: Slider.

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. The valid decimal range is 0-13. The default is 2.

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 & 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 )

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 & 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.

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 )

See also decimals.

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

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

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

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

    setRange(min, max);

is equivalent to:

    setMinimum(min);
    setMaximum(max);

See also minimum and maximum.

QString QDoubleSpinBox::textFromValue ( 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 QLocale().toString(v, QLatin1Char('f'), decimals()) and will remove the thousand seperator. 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().

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

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

void QDoubleSpinBox::valueChanged ( const 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().

double QDoubleSpinBox::valueFromText ( const QString & text ) 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: Neither prefix() nor suffix() are included when this function is called by QDoubleSpinBox.

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().