Qt 4.8: QCheckBox Class Reference

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# QCheckBox Class Reference

The QCheckBox widget provides a checkbox with a text label. More...

     #include <QCheckBox>

Inherits: QAbstractButton.

- List of all members, including inherited members
- Qt 3 support members

## Properties

- tristate : bool

- 11 properties inherited from QAbstractButton
- 58 properties inherited from QWidget
- 1 property inherited from QObject

## Public Functions

| QCheckBox ( QWidget * parent = 0 )
| QCheckBox ( const QString & text, QWidget * parent = 0 )
Qt::CheckState | checkState () const
bool | isTristate () const
void | setCheckState ( Qt::CheckState state )
void | setTristate ( bool y = true )

## Reimplemented Public Functions

virtual QSize | minimumSizeHint () const
virtual QSize | sizeHint () const

- 21 public functions inherited from QAbstractButton
- 221 public functions inherited from QWidget
- 29 public functions inherited from QObject
- 13 public functions inherited from QPaintDevice

## Signals

void | stateChanged ( int state )

- 4 signals inherited from QAbstractButton
- 1 signal inherited from QWidget
- 1 signal inherited from QObject

## Protected Functions

void | initStyleOption ( QStyleOptionButton * option ) const

## Reimplemented Protected Functions

virtual void | checkStateSet ()
virtual bool | event ( QEvent * e )
virtual bool | hitButton ( const QPoint & pos ) const
virtual void | mouseMoveEvent ( QMouseEvent * e )
virtual void | nextCheckState ()
virtual void | paintEvent ( QPaintEvent * )

- 14 protected functions inherited from QAbstractButton
- 37 protected functions inherited from QWidget
- 8 protected functions inherited from QObject
- 1 protected function inherited from QPaintDevice

### Additional Inherited Members

- 5 public slots inherited from QAbstractButton
- 19 public slots inherited from QWidget
- 1 public slot inherited from QObject
- 4 static public members inherited from QWidget
- 7 static public members inherited from QObject
- 1 protected slot inherited from QWidget

## Detailed Description

The QCheckBox widget provides a checkbox with a text label.

A QCheckBox is an option button that can be switched on (checked) or off (unchecked). Checkboxes are typically used to represent features in an application that can be enabled or disabled without affecting others, but different types of behavior can be implemented. For example, a QButtonGroup can be used to group check buttons logically, allowing exclusive checkboxes. However, QButtonGroup does not provide any visual representation.

The image below further illustrates the differences between exclusive and non-exclusive checkboxes.

Whenever a checkbox is checked or cleared it emits the signal stateChanged(). Connect to this signal if you want to trigger an action each time the checkbox changes state. You can use isChecked() to query whether or not a checkbox is checked.

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 checking nor unchecking a checkbox. If you need this third state, enable it with setTristate(), and use checkState() to query the current toggle state.

Just like QPushButton, a checkbox displays text, and optionally a small icon. The icon is set with setIcon(). The text can be set in the constructor or with setText(). A shortcut key can be specified by preceding the preferred character with an ampersand. For example:

     QCheckBox *checkbox = new QCheckBox("C&ase sensitive", this);

In this example the shortcut is Alt+A. See the QShortcut documentation for details (to display an actual ampersand, use '&&').

Important inherited functions: text(), setText(), text(), pixmap(), setPixmap(), accel(), setAccel(), isToggleButton(), setDown(), isDown(), isOn(), checkState(), autoRepeat(), isExclusiveToggle(), group(), setAutoRepeat(), toggle(), pressed(), released(), clicked(), toggled(), checkState(), and stateChanged().

| A checkbox shown in the Macintosh widget style.
| A checkbox shown in the Windows XP widget style.
| A checkbox shown in the Plastique widget style.

See also QAbstractButton, QRadioButton, and GUI Design Handbook: Check Box.

## Property Documentation

### tristate : bool

This property holds whether the checkbox is a tri-state checkbox.

The default is false; i.e. the checkbox has only two states.

Access functions:

bool | isTristate () const
void | setTristate ( bool y = true )

## Member Function Documentation

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

Constructs a checkbox with the given parent, but with no text.

parent is passed on to the QAbstractButton constructor.

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

Constructs a checkbox with the given parent and text.

parent is passed on to the QAbstractButton constructor.

### Qt::CheckState QCheckBox::checkState () const

Returns the check box's check state. If you do not need tristate support, you can also use QAbstractButton::isChecked() which returns a boolean.

See also setCheckState() and Qt::CheckState.

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

Reimplemented from QAbstractButton::checkStateSet().

### bool QCheckBox::event ( QEvent * e )`[virtual protected]`

Reimplemented from QObject::event().

### bool QCheckBox::hitButton ( const QPoint & pos ) const`[virtual protected]`

Reimplemented from QAbstractButton::hitButton().

### void QCheckBox::initStyleOption ( QStyleOptionButton * option ) const`[protected]`

Initializes option with the values from this QCheckBox. This method is useful for subclasses that require a QStyleOptionButton, but do not want to fill in all the information themselves.

See also QStyleOption::initFrom().

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

Reimplemented from QWidget::minimumSizeHint().

This function was introduced in Qt 4.8.

### void QCheckBox::mouseMoveEvent ( QMouseEvent * e )`[virtual protected]`

Reimplemented from QWidget::mouseMoveEvent().

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

Reimplemented from QAbstractButton::nextCheckState().

### void QCheckBox::paintEvent ( QPaintEvent * )`[virtual protected]`

Reimplemented from QWidget::paintEvent().

### void QCheckBox::setCheckState ( Qt::CheckState state )

Sets the check box's check state to state. If you do not need tristate support, you can also use QAbstractButton::setChecked() which takes a boolean.

See also checkState() and Qt::CheckState.

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

Reimplemented from QWidget::sizeHint().

### void QCheckBox::stateChanged ( int state )`[signal]`

This signal is emitted whenever the check box's state changes, i.e. whenever the user checks or unchecks it.

state contains the check box's new Qt::CheckState.