QAction Class Reference
^{[QtGui module]}

Detailed Description

The QAction class provides an abstract user interface action that can be inserted into widgets.

In applications many common commands can be invoked via menus, toolbar buttons, and keyboard shortcuts. Since the user expects each command to be performed in the same way, regardless of the user interface used, it is useful to represent each command as an action.

Actions can be added to menus and toolbars, and will automatically keep them in sync. For example, in a word processor, if the user presses a Bold toolbar button, the Bold menu item will automatically be checked.

Actions can be created as independent objects, but they may also be created during the construction of menus; the QMenu class contains convenience functions for creating actions suitable for use as menu items.

A QAction may contain an icon, menu text, a shortcut, status text, "What's This?" text, and a tooltip. Most of these can be set in the constructor. They can also be set independently with setIcon(), setText(), setIconText(), setShortcut(), setStatusTip(), setWhatsThis(), and setToolTip(). For menu items, it is possible to set an individual font with setFont().

Actions are added to widgets using QWidget::addAction().

Once a QAction has been created it should be added to the relevant menu and toolbar, then connected to the slot which will perform the action. For example:

        openAct = new QAction(QIcon(":/images/open.png"), tr("&Open..."), this);
        openAct->setShortcut(tr("Ctrl+O"));
        openAct->setStatusTip(tr("Open an existing file"));
        connect(openAct, SIGNAL(triggered()), this, SLOT(open()));

        fileMenu->addAction(openAct);
        fileToolBar->addAction(openAct);

We recommend that actions are created as children of the window they are used in. In most cases actions will be children of the application's main window.

Member Type Documentation

enum QAction::ActionEvent

This enum type is used when calling QAction::activate()

Property Documentation

checkable : bool

This property holds whether the action is a checkable action.

A checkable action is one which has an on/off state. For example, in a word processor, a Bold toolbar button may be either on or off. An action which is not a toggle action is a command action; a command action is simply executed, e.g. file save. By default, this property is false.

In some situations, the state of one toggle action should depend on the state of others. For example, "Left Align", "Center" and "Right Align" toggle actions are mutually exclusive. To achieve exclusive toggling, add the relevant toggle actions to a QActionGroup with the QActionGroup::exclusive property set to true.

Access functions:

• bool isCheckable () const
• void setCheckable ( bool )

See also QAction::setChecked().

checked : bool

This property holds whether the action is checked.

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

Access functions:

• bool isChecked () const
• void setChecked ( bool )

See also checkable.

enabled : bool

This property holds whether the action is enabled.

Disabled actions cannot be chosen by the user. They do not disappear from menus or toolbars, but they are displayed in a way which indicates that they are unavailable. For example, they might be displayed using only shades of gray.

What's this? help on disabled actions is still available, provided that the QAction::whatsThis property is set.

Access functions:

• bool isEnabled () const
• void setEnabled ( bool )

font : QFont

This property holds the action's font.

The font property is used to render the text set on the QAction. The font will can be considered a hint as it will not be consulted in all cases based upon application and style.

Access functions:

• QFont font () const
• void setFont ( const QFont & font )

See also QAction::setText() and QStyle.

icon : QIcon

This property holds the action's icon.

In toolbars, the icon is used as the tool button icon; in menus, it is displayed to the left of the menu text. There is no default icon.

If a null icon (QIcon::isNull() is passed into this function, the icon of the action is cleared.

Access functions:

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

iconText : QString

This property holds the action's descriptive icon text.

If QToolBar::toolButtonStyle is set to a value that permits text to be displayed, the text defined held in this property appears as a label in the relevant tool button.

It also serves as the default text in menus and tooltips if the action has not been defined with setText() or setToolTip(), and will also be used in toolbar buttons if no icon has been defined using setIcon().

If the icon text is not explicitly set, the action's normal text will be used for the icon text.

There is no default icon text.

Access functions:

• QString iconText () const
• void setIconText ( const QString & text )

See also setToolTip() and setStatusTip().

shortcut : QKeySequence

This property holds the action's shortcut key.

Valid keycodes for this property can be found in Qt::Key and Qt::Modifier. There is no default shortcut key.

Access functions:

• QKeySequence shortcut () const
• void setShortcut ( const QKeySequence & shortcut )

shortcutContext : Qt::ShortcutContext

This property holds the context for the action's shortcut.

Valid values for this property can be found in Qt::ShortcutContext. The default value is Qt::WindowShortcut.

Access functions:

• Qt::ShortcutContext shortcutContext () const
• void setShortcutContext ( Qt::ShortcutContext context )

statusTip : QString

This property holds the action's status tip.

The status tip is displayed on all status bars provided by the action's top-level parent widget.

Access functions:

• QString statusTip () const
• void setStatusTip ( const QString & statusTip )

See also setToolTip() and showStatusText().

text : QString

This property holds the action's descriptive text.

If the action is added to a menu, the menu option will consist of the icon (if there is one), the text, and the shortcut (if there is one). If the text is not explicitly set in the constructor, or by using setText(), the action's description icon text will be used as text. There is no default text.

Access functions:

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

See also iconText.

toolTip : QString

This property holds the action's tooltip.

This text is used for the tooltip. If no tooltip is specified, the action's text is used.

Access functions:

• QString toolTip () const
• void setToolTip ( const QString & tip )

See also setStatusTip() and setShortcut().

visible : bool

This property holds whether the action can be seen (e.g. in menus and toolbars).

If visible is true the action can be seen (e.g. in menus and toolbars) and chosen by the user; if visible is false the action cannot be seen or chosen by the user.

Actions which are not visible are not grayed out; they do not appear at all.

Access functions:

• bool isVisible () const
• void setVisible ( bool )

whatsThis : QString

This property holds the action's "What's This?" help text.

The "What's This?" text is used to provide a brief description of the action. The text may contain rich text. There is no default "What's This?" text.

Access functions:

• QString whatsThis () const
• void setWhatsThis ( const QString & what )

See also QWhatsThis and QStyleSheet.

Member Function Documentation

QAction::QAction ( QObject * parent )

Constructs an action with parent. If parent is an action group the action will be automatically inserted into the group.

QAction::QAction ( const QString & text, QObject * parent )

Constructs an action with some text and parent. If parent is an action group the action will be automatically inserted into the group.

The action uses a stripped version of text (e.g. "&Menu Option..." becomes "Menu Option") as descriptive text for toolbuttons. You can override this by setting a specific description with setText(). The same text will be used for tooltips unless you specify a different test using setToolTip().

QAction::QAction ( const QIcon & icon, const QString & text, QObject * parent )

Constructs an action with an icon and some text and parent. If parent is an action group the action will be automatically inserted into the group.

The action uses a stripped version of text (e.g. "&Menu Option..." becomes "Menu Option") as descriptive text for toolbuttons. You can override this by setting a specific description with setText(). The same text will be used for tooltips unless you specify a different test using setToolTip().

QAction::~QAction ()

Destroys the object and frees allocated resources.

QActionGroup * QAction::actionGroup () const

Returns the action group for this action. If no action group manages this action then 0 will be returned.

See also QActionGroup and QAction::setActionGroup().

void QAction::activate ( ActionEvent event )

Sends the relevant signals for ActionEvent event.

Action based widgets use this API to cause the QAction to emit signals as well as emitting their own.

void QAction::changed ()   [signal]

This signal is emitted when an action has changed. If you are only interested in actions in a given widget, you can watch for QWidget::actionEvent() sent with an QEvent::ActionChanged.

See also QWidget::actionEvent().

QVariant QAction::data () const

Returns the user data as set in QAction::setData.

See also setData().

void QAction::hover ()   [slot]

This is a convenience slot that calls activate(Hover).

void QAction::hovered ()   [signal]

This signal is emitted when an action is highlighted by the user; for example, when the user pauses with the cursor over a menu option, toolbar button, or presses an action's shortcut key combination.

See also QAction::activate().

bool QAction::isSeparator () const

Returns true if this action is a separator action; otherwise it returns false.

See also QAction::setSeparator().

QMenu * QAction::menu () const

Returns the menu contained by this action. Actions that contain menus can be used to create menu items with submenus, or inserted into toolbars to create buttons with popup menus.

See also setMenu() and QMenu::addAction().

QWidget * QAction::parentWidget () const

Returns the parent widget.

void QAction::setActionGroup ( QActionGroup * group )

Sets this action group to group. The action will be automatically added to the group's list of actions.

Actions within the group will be mutually exclusive.

See also QActionGroup and QAction::actionGroup().

void QAction::setData ( const QVariant & data )

Sets internal data to data. This can be used for user data to store anything that a QVariant can store. The ownership of anything the the user data will remain with the variant and thus be referenced counted as appropriate.

See also data().

void QAction::setDisabled ( bool b )   [slot]

This is a convenience function for the enabled property, that is useful for signals--slots connections. If b is true the action is disabled; otherwise it is enabled.

void QAction::setMenu ( QMenu * menu )

Sets the menu contained by this action to the specified menu.

See also menu().

void QAction::setSeparator ( bool b )

If b is true then this action will be considered a separator.

How a separator is represented depends on the widget it is inserted into. Under most circumstances the text, submenu, and icon will be ignored for separator actions.

See also QAction::isSeparator().

bool QAction::showStatusText ( QWidget * widget = 0 )

Updates the status bar for widget. If widget is an appropriate QStatusBar found for for this action based on the parent heirarchy will be used.

See also statusTip.

void QAction::toggle ()   [slot]

This is a convenience function for the checked property. Connect to it to change the checked state to its opposite state.

void QAction::toggled ( bool checked )   [signal]

This signal is emitted whenever a checkable action changes its isChecked() status. This can be the result of a user interaction, or because setChecked() was called.

checked is true if the action is checked, or false if the action is unchecked.

See also QAction::activate(), QAction::triggered(), and checked.

void QAction::trigger ()   [slot]

This is a convenience slot that calls activate(Trigger).

void QAction::triggered ( bool checked = false )   [signal]

This signal is emitted when an action is activated by the user; for example, when the user clicks a menu option, toolbar button, or presses an action's shortcut key combination, or when trigger() was called. Notably, it is not emitted when setChecked() or toggle() is called.

If the action is checkable, checked is true if the action is checked, or false if the action is unchecked.

See also QAction::activate(), QAction::toggled(), and checked.