Qt Toolkit - QCheckBox Class

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# QCheckBox Class Reference

The QCheckBox widget provides a check box with a text label. More...

`#include <qcheckbox.h>`

Inherits QButton.

List of all member functions.

## Public Members

- QCheckBox ( QWidget * parent, const char * name=0 )
- QCheckBox ( const QString & text, QWidget * parent, const char * name=0 )
- bool isChecked () const
- void setChecked ( bool check )
- void setNoChange ()
- void setTristate ( bool y=TRUE )
- bool isTristate () const

## Important Inherited Members

- QString text () const
- virtual void setText ( const QString & text )
- QString text () const
- const QPixmap* pixmap () const
- virtual void setPixmap ( const QPixmap & pixmap )
- int accel () const
- virtual void setAccel ( int key )
- bool isToggleButton () const
- virtual void setDown ( bool enable )
- bool isDown () const
- bool isOn () const
- bool autoRepeat () const
- bool isExclusiveToggle () const
- QButtonGroup* group () const
- virtual void setAutoRepeat ( bool enable )
- void toggle ()
- void pressed ()
- void released ()
- void clicked ()
- void toggled ( bool on )
- void stateChanged ( int state )

## Properties

Type | Name | READ | WRITE | Options
--- | --- | --- | --- | ---
bool | checked | isChecked | setChecked |
bool | tristate | isTristate | setTristate |

## Detailed Description

The QCheckBox widget provides a check box with a text label.

QCheckBox and QRadioButton are both option buttons. That is, they can be switched on (checked) or off (unchecked). The classes differ in how the choices for the user are restricted. Radio buttons define a "one of many" choice, while check-boxes provide "many of many" choices.

While it is technically possible to implement radio-behaviour with check boxes and vice versa, it's strongly recommended to stick with the well-known semantics. Otherwise your users would be pretty confused.

Use QButtonGroup to group check-buttons visually.

Whenver a check box is checked or cleared, it emits the signal toggled(). Connect to this signal if you want to trigger an action each time the box changes state. Otherwise, use isChecked() to query whether or not a particular check box is selected.

In addition to the usual checked and unchecked states, QCheckBox optionally provides a third state to indicate "no change". This is useful whenever you need to give the user the option of neither setting nor unsetting an option. If you need that third state, enable it with setTristate() and use state() to query the current toggle state. When a tristate box changes state, it emits the stateChanged() signal.

See also QButton, QRadioButton and Fowler: Check Box.

Examples: xform/xform.cpp i18n/main.cpp

## Member Function Documentation

### QCheckBox::QCheckBox ( QWidget * parent, const char * name=0 )

Constructs a check box with no text.

The parent and name arguments are sent to the QWidget constructor.

### QCheckBox::QCheckBox ( const QString & text, QWidget * parent, const char * name=0 )

Constructs a check box with a text.

The parent and name arguments are sent to the QWidget constructor.

### void QCheckBox::drawButton ( QPainter * paint ) `[virtual protected]`

Reimplemented for internal reasons; the API is not affected.

Reimplemented from QButton.

### void QCheckBox::drawButtonLabel ( QPainter * p ) `[virtual protected]`

Reimplemented for internal reasons; the API is not affected.

Reimplemented from QButton.

### bool QCheckBox::isChecked () const

Returns TRUE if the check box is checked, or FALSE if it is not checked.

See also setChecked().

Examples: xform/xform.cpp

### bool QCheckBox::isTristate () const

Returns TRUE if the checkbox is a tristate checkbox. Otherwise returns FALSE.

See also setTristate().

### void QCheckBox::resizeEvent ( QResizeEvent * ) `[virtual protected]`

Reimplemented for internal reasons; the API is not affected.

Reimplemented from QWidget.

### void QCheckBox::setChecked ( bool check )

Checks the check box if check is TRUE, or unchecks it if check is FALSE.

See also isChecked().

### void QCheckBox::setNoChange ()

Sets the checkbox into the "no change" state.

See also setTristate().

### void QCheckBox::setTristate ( bool y=TRUE )

Makes the check box a tristate check box if y is TRUE. A tristate check box provides an additional state NoChange.

Use tristate check boxes whenever you need to give the user the option of neither setting nor unsetting an option. A typical example is the "Italic" check box in the font dialog of a word processor when the marked text is partially Italic and partially not.

See also isTristate(), setNoChange(), stateChanged() and state().

### QSize QCheckBox::sizeHint () const `[virtual]`

Reimplemented for internal reasons; the API is not affected.

Reimplemented from QWidget.

### QSizePolicy QCheckBox::sizePolicy () const `[virtual]`

Reimplemented for internal reasons; the API is not affected.

Reimplemented from QWidget.

### void QCheckBox::updateMask () `[virtual protected]`

Reimplemented for internal reasons; the API is not affected.

Reimplemented from QWidget.

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