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# QAbstractButton Class Reference

The QAbstractButton class is the abstract base class of button widgets, providing functionality common to buttons. More...

    #include <QAbstractButton>

Inherits QWidget.

Inherited by Q3Button, QCheckBox, QPushButton, QRadioButton, and QToolButton.

- List of all members, including inherited members
- Compatibility members

### Writable Properties

- autoExclusive : bool
- autoRepeat : bool
- checkable : bool
- checked : bool

- down : bool
- icon : QIcon
- shortcut : QKeySequence
- text : QString

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

### Read-Only Properties

- 20 read-only properties inherited from QWidget

### Public Functions

- QAbstractButton ( QWidget * parent = 0 )
- ~QAbstractButton ()
- QButtonGroup * group () const

- 92 public functions inherited from QWidget
- 26 public functions inherited from QObject
- 10 public functions inherited from QPaintDevice

### Public Slots

- void animateClick ( int msec = 100 )
- void click ()
- void setChecked ( bool )
- void toggle ()

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

### Signals

- void clicked ()
- void pressed ()
- void released ()
- void toggled ( bool checked )

- 1 signal inherited from QObject

### Static Public Members

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

### Protected Functions

- virtual void checkStateSet ()
- virtual bool hitButton ( const QPoint & pos ) const
- virtual void nextCheckState ()

- 42 protected functions inherited from QWidget
- 7 protected functions inherited from QObject

## Detailed Description

The QAbstractButton class is the abstract base class of button widgets, providing functionality common to buttons.

This class implements an abstract button. Subclasses of this class handle user actions, and specify how the button is drawn.

QAbstractButton provides support for both push buttons and checkable (toggle) buttons. Checkable buttons are implemented in the QRadioButton and QCheckBox classes. Push buttons are implemented in the QPushButton and QToolButton classes; these also provide toggle behavior if required.

Any button can display a label containing text and an icon. setText() sets the text; setIcon() sets the icon. If a button is disabled, its label is changed to give the button a "disabled" appearance.

If the button is a text button with a string containing an ampersand (&), QButton creates an automatic shortcut key, called a mnemonic, that may change based on the button translation. The following code creates a push button labelled "Rock & Roll" (where the c is underlined):

        QPushButton *p = new QPushButton("Ro&ck && Roll", this);

In this example, the shortcut Alt+C is assigned to the button, so that when the user presses Alt+C the button will call animateClick().

You can also set a custom shortcut key using the setShortcut() function. This is useful mostly for buttons that do not have any text, because they have no automatic shortcut.

        p->setPixmap(QPixmap("print.png"));
        p->setShortcut(Qt::ALT+Qt::Key_F7);

All of the buttons provided by Qt (QPushButton, QToolButton, QCheckBox and QRadioButton) can display both text and pixmaps.

A button can be made the default button in a dialog are provided by QPushButton::setDefault() and QPushButton::setAutoDefault().

QAbstractButton provides most of the states used for buttons:

- isDown() indicates whether the button is pressed down.
- isChecked() indicates whether the button is checked. Only checkable buttons can be checked and unchecked (see below).
- isEnabled() indicates whether the button can be pressed by the user.
- setAutoRepeat() sets whether the button will auto-repeat if the user holds it down.
- setCheckable() sets whether the button is a toggle button or not.

The difference between isDown() and isChecked() is as follows. When the user clicks a toggle button to check it, the button is first pressed then released into the checked state. When the user clicks it again (to uncheck it), the button moves first to the pressed state, then to the unchecked state (isChecked() and isDown() are both false).

QButton provides five signals:

1. pressed() is emitted when the left mouse button is pressed while the mouse cursor is inside the button.
2. released() is emitted when the left mouse button is released.
3. clicked() is emitted when the button is first pressed and then released when the shortcut key is typed, or when animateClick() is called.
4. toggled(bool) is emitted when the state of a toggle button changes.

To subclass QAbstractButton, you must reimplement at least paintEvent() to draw the button's outline and its text or pixmap. It is generally advisable to reimplement sizeHint() as well, and sometimes hitButton() (to determine whether a button press is within the button). For buttons with more than two states (like tri-state buttons), you will also have to reimplement checkStateSet() and nextCheckState().

See also QButtonGroup.

## Property Documentation

### autoExclusive : bool

This property holds whether is enabled.

If autoExclusive is enabled, checkable buttons that belong to the same parent widget behave as if they were part of the same exclusive button group. In an exclusive button group, only one button can be checked at any time; checking another button automatically unchecks the previously checked one.

The property has no effect on buttons that belong to a button group.

autoExclusive is off by default, except for radio buttons.

Access functions:

- bool autoExclusive () const
- void setAutoExclusive ( bool )

See also QRadioButton.

### autoRepeat : bool

This property holds whether is enabled.

If autoRepeat is enabled then the clicked() signal is emitted at regular intervals when the button is down. This property has no effect on toggle buttons. autoRepeat is off by default.

Access functions:

- bool autoRepeat () const
- void setAutoRepeat ( bool )

### checkable : bool

This property holds whether the button is checkable.

By default, this is false (the button is not checkable).

Access functions:

- bool isCheckable () const
- void setCheckable ( bool )

See also checked.

### checked : bool

This property holds whether the button is checked.

Only checkable buttons can be checked. By default, this is false (the button is unchecked).

Access functions:

- bool isChecked () const
- void setChecked ( bool )

See also checkable.

### down : bool

This property holds whether the button is pressed down.

If this property is true, the button is pressed down. The signals pressed() and clicked() are not emitted if you set this property to true. The default is false.

Access functions:

- bool isDown () const
- void setDown ( bool )

### icon : QIcon

This property holds the icon shown on the button.

Access functions:

- QIcon icon () const
- void setIcon ( const QIcon & icon )

### shortcut : QKeySequence

This property holds the mnemonic associated with the button.

Access functions:

- QKeySequence shortcut () const
- void setShortcut ( const QKeySequence & key )

### text : QString

This property holds the text shown on the button.

This property will return a an empty string if the button has no text. If the text contains an ampersand character (&), a mnemonic is automatically created for it. The character that follows the '&' will be used as the shortcut key. Any previous mnemonic will be overwritten, or cleared if no mnemonic is defined by the text.

There is no default text.

Access functions:

- QString text () const
- void setText ( const QString & text )

## Member Function Documentation

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

Constructs an abstract button with a parent.

### QAbstractButton::~QAbstractButton ()

Destroys the button.

### void QAbstractButton::animateClick ( int msec = 100 ) `[slot]`

Performs an animated click: the button is pressed and released msec milliseconds later (the default is 100 msecs).

All signals associated with a click are emitted as appropriate.

This function does nothing if the button is disabled.

See also click().

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

This virtual handler is called when setChecked() was called, unless it was called from within nextCheckState(). It allows subclasses to reset their intermediate button states.

See also nextCheckState().

### void QAbstractButton::click () `[slot]`

Performs a click.

All the usual signals associated with a click are emitted as appropriate.

This function does nothing if the button is disabled.

See also animateClick().

### void QAbstractButton::clicked () `[signal]`

This signal is emitted when the button is activated (i.e. pressed down then released while the mouse cursor is inside the button), when the shortcut key is typed, or when animateClick() is called. This signal is not emitted if you call setDown().

See also pressed(), released(), and toggled().

### QButtonGroup * QAbstractButton::group () const

Returns the group that this button belongs to.

If the button is not a member of any QButtonGroup, this function returns 0.

See also QButtonGroup.

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

Returns true if pos is inside the clickable button rectangle; otherwise returns false.

By default, the clickable area is the entire widget. Subclasses may reimplement this function to provide support for clickable areas of different shapes and sizes.

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

This virtual handler is called when a button is clicked. The default implementation calls setChecked(!isChecked()) if the button isCheckable(). It allows subclasses to implement intermediate button states.

See also checkStateSet().

### void QAbstractButton::pressed () `[signal]`

This signal is emitted when the button is pressed down.

See also released() and clicked().

### void QAbstractButton::released () `[signal]`

This signal is emitted when the button is released.

See also pressed(), clicked(), and toggled().

### void QAbstractButton::toggle () `[slot]`

Toggles the state of a checkable button.

See also checked.

### void QAbstractButton::toggled ( bool checked ) `[signal]`

This signal is emitted whenever a toggle button changes its state. checked is true if the button is checked, or false if the button is unchecked.

This may be the result of a user action, toggle() slot activation, or because setChecked() was called.

See also clicked().