QComboBox Class

The QComboBox widget is a combined button and popup list. More...

Header:	#include <QComboBox>
qmake:	QT += widgets
Inherits:	QWidget
Inherited By:	QFontComboBox

• List of all members, including inherited members
• Obsolete members

Public Types

enum	InsertPolicy { NoInsert, InsertAtTop, InsertAtCurrent, InsertAtBottom, InsertAfterCurrent, …, InsertAlphabetically }
enum	SizeAdjustPolicy { AdjustToContents, AdjustToContentsOnFirstShow, AdjustToMinimumContentsLength, AdjustToMinimumContentsLengthWithIcon }

Properties

count : const int currentData : const QVariant currentIndex : int currentText : QString duplicatesEnabled : bool editable : bool frame : bool

iconSize : QSize insertPolicy : InsertPolicy maxCount : int maxVisibleItems : int minimumContentsLength : int modelColumn : int sizeAdjustPolicy : SizeAdjustPolicy

Public Functions

	QComboBox(QWidget *parent = nullptr)
virtual	~QComboBox()
void	addItem(const QString &text, const QVariant &userData = QVariant())
void	addItem(const QIcon &icon, const QString &text, const QVariant &userData = QVariant())
void	addItems(const QStringList &texts)
QCompleter *	completer() const
int	count() const
QVariant	currentData(int role = Qt::UserRole) const
int	currentIndex() const
QString	currentText() const
bool	duplicatesEnabled() const
int	findData(const QVariant &data, int role = Qt::UserRole, Qt::MatchFlags flags = static_cast<Qt::MatchFlags>(Qt::MatchExactly|Qt::MatchCaseSensitive)) const
int	findText(const QString &text, Qt::MatchFlags flags = ...) const
bool	hasFrame() const
virtual void	hidePopup()
QSize	iconSize() const
void	insertItem(int index, const QString &text, const QVariant &userData = QVariant())
void	insertItem(int index, const QIcon &icon, const QString &text, const QVariant &userData = QVariant())
void	insertItems(int index, const QStringList &list)
QComboBox::InsertPolicy	insertPolicy() const
void	insertSeparator(int index)
bool	isEditable() const
QVariant	itemData(int index, int role = Qt::UserRole) const
QAbstractItemDelegate *	itemDelegate() const
QIcon	itemIcon(int index) const
QString	itemText(int index) const
QLineEdit *	lineEdit() const
int	maxCount() const
int	maxVisibleItems() const
int	minimumContentsLength() const
QAbstractItemModel *	model() const
int	modelColumn() const
void	removeItem(int index)
QModelIndex	rootModelIndex() const
void	setCompleter(QCompleter *completer)
void	setDuplicatesEnabled(bool enable)
void	setEditable(bool editable)
void	setFrame(bool)
void	setIconSize(const QSize &size)
void	setInsertPolicy(QComboBox::InsertPolicy policy)
void	setItemData(int index, const QVariant &value, int role = Qt::UserRole)
void	setItemDelegate(QAbstractItemDelegate *delegate)
void	setItemIcon(int index, const QIcon &icon)
void	setItemText(int index, const QString &text)
void	setLineEdit(QLineEdit *edit)
void	setMaxCount(int max)
void	setMaxVisibleItems(int maxItems)
void	setMinimumContentsLength(int characters)
void	setModel(QAbstractItemModel *model)
void	setModelColumn(int visibleColumn)
void	setRootModelIndex(const QModelIndex &index)
void	setSizeAdjustPolicy(QComboBox::SizeAdjustPolicy policy)
void	setValidator(const QValidator *validator)
void	setView(QAbstractItemView *itemView)
virtual void	showPopup()
QComboBox::SizeAdjustPolicy	sizeAdjustPolicy() const
const QValidator *	validator() const
QAbstractItemView *	view() const

Reimplemented Public Functions

virtual bool	event(QEvent *event) override
virtual QVariant	inputMethodQuery(Qt::InputMethodQuery query) const override
virtual QSize	minimumSizeHint() const override
virtual QSize	sizeHint() const override

Public Slots

void	clear()
void	clearEditText()
void	setCurrentIndex(int index)
void	setCurrentText(const QString &text)
void	setEditText(const QString &text)

Signals

void	activated(int index)
void	currentIndexChanged(const QString &text)
void	currentIndexChanged(int index)
void	currentTextChanged(const QString &text)
void	editTextChanged(const QString &text)
void	highlighted(int index)
void	textActivated(const QString &text)
void	textHighlighted(const QString &text)

Protected Functions

void	initStyleOption(QStyleOptionComboBox *option) const

Reimplemented Protected Functions

virtual void	changeEvent(QEvent *e) override
virtual void	contextMenuEvent(QContextMenuEvent *e) override
virtual void	focusInEvent(QFocusEvent *e) override
virtual void	focusOutEvent(QFocusEvent *e) override
virtual void	hideEvent(QHideEvent *e) override
virtual void	inputMethodEvent(QInputMethodEvent *e) override
virtual void	keyPressEvent(QKeyEvent *e) override
virtual void	keyReleaseEvent(QKeyEvent *e) override
virtual void	mousePressEvent(QMouseEvent *e) override
virtual void	mouseReleaseEvent(QMouseEvent *e) override
virtual void	paintEvent(QPaintEvent *e) override
virtual void	resizeEvent(QResizeEvent *e) override
virtual void	showEvent(QShowEvent *e) override
virtual void	wheelEvent(QWheelEvent *e) override

Detailed Description

A QComboBox provides a means of presenting a list of options to the user in a way that takes up the minimum amount of screen space.

A combobox is a selection widget that displays the current item, and can pop up a list of selectable items. A combobox may be editable, allowing the user to modify each item in the list.

Comboboxes can contain pixmaps as well as strings; the insertItem() and setItemText() functions are suitably overloaded. For editable comboboxes, the function clearEditText() is provided, to clear the displayed string without changing the combobox's contents.

There are two signals emitted if the current item of a combobox changes, currentIndexChanged() and activated(). currentIndexChanged() is always emitted regardless if the change was done programmatically or by user interaction, while activated() is only emitted when the change is caused by user interaction. The highlighted() signal is emitted when the user highlights an item in the combobox popup list. All three signals exist in two versions, one with a QString argument and one with an int argument. If the user selects or highlights a pixmap, only the int signals are emitted. Whenever the text of an editable combobox is changed the editTextChanged() signal is emitted.

When the user enters a new string in an editable combobox, the widget may or may not insert it, and it can insert it in several locations. The default policy is InsertAtBottom but you can change this using setInsertPolicy().

It is possible to constrain the input to an editable combobox using QValidator; see setValidator(). By default, any input is accepted.

A combobox can be populated using the insert functions, insertItem() and insertItems() for example. Items can be changed with setItemText(). An item can be removed with removeItem() and all items can be removed with clear(). The text of the current item is returned by currentText(), and the text of a numbered item is returned with text(). The current item can be set with setCurrentIndex(). The number of items in the combobox is returned by count(); the maximum number of items can be set with setMaxCount(). You can allow editing using setEditable(). For editable comboboxes you can set auto-completion using setCompleter() and whether or not the user can add duplicates is set with setDuplicatesEnabled().

QComboBox uses the model/view framework for its popup list and to store its items. By default a QStandardItemModel stores the items and a QListView subclass displays the popuplist. You can access the model and view directly (with model() and view()), but QComboBox also provides functions to set and get item data (e.g., setItemData() and itemText()). You can also set a new model and view (with setModel() and setView()). For the text and icon in the combobox label, the data in the model that has the Qt::DisplayRole and Qt::DecorationRole is used. Note that you cannot alter the SelectionMode of the view(), e.g., by using setSelectionMode().

See also QLineEdit, QSpinBox, QRadioButton, QButtonGroup, and GUI Design Handbook: Combo Box, Drop-Down List Box.

Member Type Documentation

enum QComboBox::InsertPolicy

This enum specifies what the QComboBox should do when a new string is entered by the user.

Constant	Value	Description
QComboBox::NoInsert	0	The string will not be inserted into the combobox.
QComboBox::InsertAtTop	1	The string will be inserted as the first item in the combobox.
QComboBox::InsertAtCurrent	2	The current item will be replaced by the string.
QComboBox::InsertAtBottom	3	The string will be inserted after the last item in the combobox.
QComboBox::InsertAfterCurrent	4	The string is inserted after the current item in the combobox.
QComboBox::InsertBeforeCurrent	5	The string is inserted before the current item in the combobox.
QComboBox::InsertAlphabetically	6	The string is inserted in the alphabetic order in the combobox.

enum QComboBox::SizeAdjustPolicy

This enum specifies how the size hint of the QComboBox should adjust when new content is added or content changes.

Constant	Value	Description
QComboBox::AdjustToContents	0	The combobox will always adjust to the contents
QComboBox::AdjustToContentsOnFirstShow	1	The combobox will adjust to its contents the first time it is shown.
QComboBox::AdjustToMinimumContentsLength	2	Use AdjustToContents or AdjustToContentsOnFirstShow instead.
QComboBox::AdjustToMinimumContentsLengthWithIcon	3	The combobox will adjust to minimumContentsLength plus space for an icon. For performance reasons use this policy on large models.

Member Function Documentation

QComboBox::QComboBox(QWidget *parent = nullptr)

Constructs a combobox with the given parent, using the default model QStandardItemModel.

[signal] void QComboBox::activated(int index)

This signal is sent when the user chooses an item in the combobox. The item's index is passed. Note that this signal is sent even when the choice is not changed. If you need to know when the choice actually changes, use signal currentIndexChanged().

Note: Signal activated is overloaded in this class. To connect to this signal by using the function pointer syntax, Qt provides a convenient helper for obtaining the function pointer as shown in this example:

connect(comboBox, QOverload<int>::of(&QComboBox::activated),
    [=](int index){ /* ... */ });

[slot] void QComboBox::clear()

Clears the combobox, removing all items.

Note: If you have set an external model on the combobox this model will still be cleared when calling this function.

[slot] void QComboBox::clearEditText()

Clears the contents of the line edit used for editing in the combobox.

[signal] void QComboBox::currentIndexChanged(const QString &text)

This signal is sent whenever the currentIndex in the combobox changes either through user interaction or programmatically. The item's text is passed.

Note: Signal currentIndexChanged is overloaded in this class. To connect to this signal by using the function pointer syntax, Qt provides a convenient helper for obtaining the function pointer as shown in this example:

connect(comboBox, QOverload<const QString &>::of(&QComboBox::currentIndexChanged),
    [=](const QString &text){ /* ... */ });

This function was introduced in Qt 4.1.

Note: Notifier signal for property currentIndex.

[signal] void QComboBox::currentIndexChanged(int index)

This signal is sent whenever the currentIndex in the combobox changes either through user interaction or programmatically. The item's index is passed or -1 if the combobox becomes empty or the currentIndex was reset.

Note: Signal currentIndexChanged is overloaded in this class. To connect to this signal by using the function pointer syntax, Qt provides a convenient helper for obtaining the function pointer as shown in this example:

connect(comboBox, QOverload<int>::of(&QComboBox::currentIndexChanged),
    [=](int index){ /* ... */ });

This function was introduced in Qt 4.1.

Note: Notifier signal for property currentIndex.

[signal] void QComboBox::currentTextChanged(const QString &text)

This signal is sent whenever currentText changes. The new value is passed as text.

This function was introduced in Qt 5.0.

Note: Notifier signal for property currentText.

[signal] void QComboBox::editTextChanged(const QString &text)

This signal is emitted when the text in the combobox's line edit widget is changed. The new text is specified by text.

[signal] void QComboBox::highlighted(int index)

This signal is sent when an item in the combobox popup list is highlighted by the user. The item's index is passed.

Note: Signal highlighted is overloaded in this class. To connect to this signal by using the function pointer syntax, Qt provides a convenient helper for obtaining the function pointer as shown in this example:

connect(comboBox, QOverload<int>::of(&QComboBox::highlighted),
    [=](int index){ /* ... */ });

[slot] void QComboBox::setEditText(const QString &text)

Sets the text in the combobox's text edit.

[signal] void QComboBox::textActivated(const QString &text)

This signal is sent when the user chooses an item in the combobox. The item's text is passed. Note that this signal is sent even when the choice is not changed. If you need to know when the choice actually changes, use signal currentIndexChanged().

This function was introduced in Qt 5.14.

[signal] void QComboBox::textHighlighted(const QString &text)

This signal is sent when an item in the combobox popup list is highlighted by the user. The item's text is passed.

This function was introduced in Qt 5.14.

[virtual] QComboBox::~QComboBox()

Destroys the combobox.

void QComboBox::addItem(const QString &text, const QVariant &userData = QVariant())

Adds an item to the combobox with the given text, and containing the specified userData (stored in the Qt::UserRole). The item is appended to the list of existing items.

void QComboBox::addItem(const QIcon &icon, const QString &text, const QVariant &userData = QVariant())

Adds an item to the combobox with the given icon and text, and containing the specified userData (stored in the Qt::UserRole). The item is appended to the list of existing items.

void QComboBox::addItems(const QStringList &texts)

Adds each of the strings in the given texts to the combobox. Each item is appended to the list of existing items in turn.

[override virtual protected] void QComboBox::changeEvent(QEvent *e)

Reimplements: QWidget::changeEvent(QEvent *event).

QCompleter *QComboBox::completer() const

Returns the completer that is used to auto complete text input for the combobox.

This function was introduced in Qt 4.2.

See also setCompleter() and editable.

[override virtual protected] void QComboBox::contextMenuEvent(QContextMenuEvent *e)

Reimplements: QWidget::contextMenuEvent(QContextMenuEvent *event).

[override virtual] bool QComboBox::event(QEvent *event)

Reimplements: QWidget::event(QEvent *event).

int QComboBox::findData(const QVariant &data, int role = Qt::UserRole, Qt::MatchFlags flags = static_cast<Qt::MatchFlags>(Qt::MatchExactly|Qt::MatchCaseSensitive)) const

Returns the index of the item containing the given data for the given role; otherwise returns -1.

The flags specify how the items in the combobox are searched.

int QComboBox::findText(const QString &text, Qt::MatchFlags flags = ...) const

Returns the index of the item containing the given text; otherwise returns -1.

The flags specify how the items in the combobox are searched.

[override virtual protected] void QComboBox::focusInEvent(QFocusEvent *e)

Reimplements: QWidget::focusInEvent(QFocusEvent *event).

[override virtual protected] void QComboBox::focusOutEvent(QFocusEvent *e)

Reimplements: QWidget::focusOutEvent(QFocusEvent *event).

[override virtual protected] void QComboBox::hideEvent(QHideEvent *e)

Reimplements: QWidget::hideEvent(QHideEvent *event).

[virtual] void QComboBox::hidePopup()

Hides the list of items in the combobox if it is currently visible and resets the internal state, so that if the custom pop-up was shown inside the reimplemented showPopup(), then you also need to reimplement the hidePopup() function to hide your custom pop-up and call the base class implementation to reset the internal state whenever your custom pop-up widget is hidden.

See also showPopup().

[protected] void QComboBox::initStyleOption(QStyleOptionComboBox *option) const

Initialize option with the values from this QComboBox. This method is useful for subclasses when they need a QStyleOptionComboBox, but don't want to fill in all the information themselves.

See also QStyleOption::initFrom().

[override virtual protected] void QComboBox::inputMethodEvent(QInputMethodEvent *e)

Reimplements: QWidget::inputMethodEvent(QInputMethodEvent *event).

[override virtual] QVariant QComboBox::inputMethodQuery(Qt::InputMethodQuery query) const

Reimplements: QWidget::inputMethodQuery(Qt::InputMethodQuery query) const.

void QComboBox::insertItem(int index, const QString &text, const QVariant &userData = QVariant())

Inserts the text and userData (stored in the Qt::UserRole) into the combobox at the given index.

If the index is equal to or higher than the total number of items, the new item is appended to the list of existing items. If the index is zero or negative, the new item is prepended to the list of existing items.

See also insertItems().

void QComboBox::insertItem(int index, const QIcon &icon, const QString &text, const QVariant &userData = QVariant())

Inserts the icon, text and userData (stored in the Qt::UserRole) into the combobox at the given index.

If the index is equal to or higher than the total number of items, the new item is appended to the list of existing items. If the index is zero or negative, the new item is prepended to the list of existing items.

See also insertItems().

void QComboBox::insertItems(int index, const QStringList &list)

Inserts the strings from the list into the combobox as separate items, starting at the index specified.

If the index is equal to or higher than the total number of items, the new items are appended to the list of existing items. If the index is zero or negative, the new items are prepended to the list of existing items.

See also insertItem().

void QComboBox::insertSeparator(int index)

Inserts a separator item into the combobox at the given index.

If the index is equal to or higher than the total number of items, the new item is appended to the list of existing items. If the index is zero or negative, the new item is prepended to the list of existing items.

This function was introduced in Qt 4.4.

See also insertItem().

QVariant QComboBox::itemData(int index, int role = Qt::UserRole) const

Returns the data for the given role in the given index in the combobox, or QVariant::Invalid if there is no data for this role.

See also setItemData().

QAbstractItemDelegate *QComboBox::itemDelegate() const

Returns the item delegate used by the popup list view.

See also setItemDelegate().

QIcon QComboBox::itemIcon(int index) const

Returns the icon for the given index in the combobox.

See also setItemIcon().

QString QComboBox::itemText(int index) const

Returns the text for the given index in the combobox.

See also setItemText().

[override virtual protected] void QComboBox::keyPressEvent(QKeyEvent *e)

Reimplements: QWidget::keyPressEvent(QKeyEvent *event).

[override virtual protected] void QComboBox::keyReleaseEvent(QKeyEvent *e)

Reimplements: QWidget::keyReleaseEvent(QKeyEvent *event).

QLineEdit *QComboBox::lineEdit() const

Returns the line edit used to edit items in the combobox, or nullptr if there is no line edit.

Only editable combo boxes have a line edit.

See also setLineEdit().

[override virtual] QSize QComboBox::minimumSizeHint() const

Reimplements an access function for property: QWidget::minimumSizeHint.

QAbstractItemModel *QComboBox::model() const

Returns the model used by the combobox.

See also setModel().

[override virtual protected] void QComboBox::mousePressEvent(QMouseEvent *e)

Reimplements: QWidget::mousePressEvent(QMouseEvent *event).

[override virtual protected] void QComboBox::mouseReleaseEvent(QMouseEvent *e)

Reimplements: QWidget::mouseReleaseEvent(QMouseEvent *event).

[override virtual protected] void QComboBox::paintEvent(QPaintEvent *e)

Reimplements: QWidget::paintEvent(QPaintEvent *event).

void QComboBox::removeItem(int index)

Removes the item at the given index from the combobox. This will update the current index if the index is removed.

This function does nothing if index is out of range.

[override virtual protected] void QComboBox::resizeEvent(QResizeEvent *e)

Reimplements: QWidget::resizeEvent(QResizeEvent *event).

QModelIndex QComboBox::rootModelIndex() const

Returns the root model item index for the items in the combobox.

See also setRootModelIndex().

void QComboBox::setCompleter(QCompleter *completer)

Sets the completer to use instead of the current completer. If completer is 0, auto completion is disabled.

By default, for an editable combo box, a QCompleter that performs case insensitive inline completion is automatically created.

Note: The completer is removed when the editable property becomes false. Setting a completer on a QComboBox that is not editable will be ignored.

This function was introduced in Qt 4.2.

See also completer().

void QComboBox::setItemData(int index, const QVariant &value, int role = Qt::UserRole)

Sets the data role for the item on the given index in the combobox to the specified value.

See also itemData().

void QComboBox::setItemDelegate(QAbstractItemDelegate *delegate)

Sets the item delegate for the popup list view. The combobox takes ownership of the delegate.

Warning: You should not share the same instance of a delegate between comboboxes, widget mappers or views. Doing so can cause incorrect or unintuitive editing behavior since each view connected to a given delegate may receive the closeEditor() signal, and attempt to access, modify or close an editor that has already been closed.

See also itemDelegate().

void QComboBox::setItemIcon(int index, const QIcon &icon)

Sets the icon for the item on the given index in the combobox.

See also itemIcon().

void QComboBox::setItemText(int index, const QString &text)

Sets the text for the item on the given index in the combobox.

See also itemText().

void QComboBox::setLineEdit(QLineEdit *edit)

Sets the line edit to use instead of the current line edit widget.

The combo box takes ownership of the line edit.

See also lineEdit().

void QComboBox::setModel(QAbstractItemModel *model)

Sets the model to be model. model must not be nullptr. If you want to clear the contents of a model, call clear().

See also model() and clear().

void QComboBox::setRootModelIndex(const QModelIndex &index)

Sets the root model item index for the items in the combobox.

See also rootModelIndex().

void QComboBox::setValidator(const QValidator *validator)

Sets the validator to use instead of the current validator.

Note: The validator is removed when the editable property becomes false.

See also validator().

void QComboBox::setView(QAbstractItemView *itemView)

Sets the view to be used in the combobox popup to the given itemView. The combobox takes ownership of the view.

Note: If you want to use the convenience views (like QListWidget, QTableWidget or QTreeWidget), make sure to call setModel() on the combobox with the convenience widgets model before calling this function.

See also view().

[override virtual protected] void QComboBox::showEvent(QShowEvent *e)

Reimplements: QWidget::showEvent(QShowEvent *event).

[virtual] void QComboBox::showPopup()

Displays the list of items in the combobox. If the list is empty then no items will be shown.

If you reimplement this function to show a custom pop-up, make sure you call hidePopup() to reset the internal state.

See also hidePopup().

[override virtual] QSize QComboBox::sizeHint() const

Reimplements an access function for property: QWidget::sizeHint.

This implementation caches the size hint to avoid resizing when the contents change dynamically. To invalidate the cached value change the sizeAdjustPolicy.

const QValidator *QComboBox::validator() const

Returns the validator that is used to constrain text input for the combobox.

See also setValidator() and editable.

QAbstractItemView *QComboBox::view() const

Returns the list view used for the combobox popup.

See also setView().

[override virtual protected] void QComboBox::wheelEvent(QWheelEvent *e)

Reimplements: QWidget::wheelEvent(QWheelEvent *event).