QMessageBox Class

 QMessageBox msgBox;
 msgBox.setText("The document has been modified.");
 msgBox.exec();

 QMessageBox msgBox;
 msgBox.setText("The document has been modified.");
 msgBox.setInformativeText("Do you want to save your changes?");
 msgBox.setStandardButtons(QMessageBox::Save | QMessageBox::Discard | QMessageBox::Cancel);
 msgBox.setDefaultButton(QMessageBox::Save);
 int ret = msgBox.exec();

 switch (ret) {
   case QMessageBox::Save:
       // Save was clicked
       break;
   case QMessageBox::Discard:
       // Don't Save was clicked
       break;
   case QMessageBox::Cancel:
       // Cancel was clicked
       break;
   default:
       // should never be reached
       break;
 }

 int ret = QMessageBox::warning(this, tr("My Application"),
                                tr("The document has been modified.\n"
                                   "Do you want to save your changes?"),
                                QMessageBox::Save | QMessageBox::Discard
                                | QMessageBox::Cancel,
                                QMessageBox::Save);

 QMessageBox msgBox;
 QPushButton *connectButton = msgBox.addButton(tr("Connect"), QMessageBox::ActionRole);
 QPushButton *abortButton = msgBox.addButton(QMessageBox::Abort);

 msgBox.exec();

 if (msgBox.clickedButton() == connectButton) {
     // connect
 } else if (msgBox.clickedButton() == abortButton) {
     // abort
 }

Member Function Documentation

QMessageBox::QMessageBox(Icon icon, const QString &title, const QString &text, StandardButtons buttons = NoButton, QWidget *parent = nullptr, Qt::WindowFlags f = Qt::Dialog | Qt::MSWindowsFixedSizeDialogHint)

Constructs a message box with the given icon, title, text, and standard buttons. Standard or custom buttons can be added at any time using addButton(). The parent and f arguments are passed to the QDialog constructor.

The message box is an application modal dialog box.

On macOS, if parent is not nullptr and you want your message box to appear as a Qt::Sheet of that parent, set the message box's window modality to Qt::WindowModal (default). Otherwise, the message box will be a standard dialog.

See also setWindowTitle(), setText(), setIcon(), and setStandardButtons().

QMessageBox::QMessageBox(QWidget *parent = nullptr)

Constructs a message box with no text and no buttons. parent is passed to the QDialog constructor.

On macOS, if you want your message box to appear as a Qt::Sheet of its parent, set the message box's window modality to Qt::WindowModal or use open(). Otherwise, the message box will be a standard dialog.

[signal] void QMessageBox::buttonClicked(QAbstractButton *button)

This signal is emitted whenever a button is clicked inside the QMessageBox. The button that was clicked in returned in button.

[override virtual slot] int QMessageBox::exec()

Reimplements: QDialog::exec().

Shows the message box as a modal dialog, blocking until the user closes it.

When using a QMessageBox with standard buttons, this function returns a StandardButton value indicating the standard button that was clicked. When using QMessageBox with custom buttons, this function returns an opaque value; use clickedButton() to determine which button was clicked.

Users cannot interact with any other window in the same application until they close the dialog, either by clicking a button or by using a mechanism provided by the window system.

See also show() and result().

[virtual] QMessageBox::~QMessageBox()

Destroys the message box.

[static] void QMessageBox::about(QWidget *parent, const QString &title, const QString &text)

Displays a simple about box with title title and text text. The about box's parent is parent.

about() looks for a suitable icon in four locations:

1. It prefers parent->icon() if that exists.
2. If not, it tries the top-level widget containing parent.
3. If that fails, it tries the active window.
4. As a last resort it uses the Information icon.

The about box has a single button labelled "OK". On macOS, the about box is popped up as a modeless window; on other platforms, it is currently application modal.

See also QWidget::windowIcon() and QApplication::activeWindow().

[static] void QMessageBox::aboutQt(QWidget *parent, const QString &title = QString())

Displays a simple message box about Qt, with the given title and centered over parent (if parent is not nullptr). The message includes the version number of Qt being used by the application.

This is useful for inclusion in the Help menu of an application, as shown in the Menus example.

QApplication provides this functionality as a slot.

On macOS, the about box is popped up as a modeless window; on other platforms, it is currently application modal.

See also QApplication::aboutQt().

void QMessageBox::addButton(QAbstractButton *button, ButtonRole role)

Adds the given button to the message box with the specified role.

This function was introduced in Qt 4.2.

See also removeButton(), button(), and setStandardButtons().

QPushButton *QMessageBox::addButton(const QString &text, ButtonRole role)

This is an overloaded function.

Creates a button with the given text, adds it to the message box for the specified role, and returns it.

This function was introduced in Qt 4.2.

QPushButton *QMessageBox::addButton(StandardButton button)

This is an overloaded function.

Adds a standard button to the message box if it is valid to do so, and returns the push button.

This function was introduced in Qt 4.2.

See also setStandardButtons().

QAbstractButton *QMessageBox::button(StandardButton which) const

Returns a pointer corresponding to the standard button which, or nullptr if the standard button doesn't exist in this message box.

This function was introduced in Qt 4.2.

See also standardButtons and standardButton().

ButtonRole QMessageBox::buttonRole(QAbstractButton *button) const

Returns the button role for the specified button. This function returns InvalidRole if button is nullptr or has not been added to the message box.

This function was introduced in Qt 4.5.

See also buttons() and addButton().

QList<QAbstractButton *> QMessageBox::buttons() const

Returns a list of all the buttons that have been added to the message box.

This function was introduced in Qt 4.5.

See also buttonRole(), addButton(), and removeButton().

[override virtual protected] void QMessageBox::changeEvent(QEvent *ev)

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

QCheckBox *QMessageBox::checkBox() const

Returns the checkbox shown on the dialog. This is nullptr if no checkbox is set.

This function was introduced in Qt 5.2.

See also setCheckBox().

QAbstractButton *QMessageBox::clickedButton() const

Returns the button that was clicked by the user, or nullptr if the user hit the Esc key and no escape button was set.

If exec() hasn't been called yet, returns nullptr.

Example:

 QMessageBox messageBox(this);
 QAbstractButton *disconnectButton =
       messageBox.addButton(tr("Disconnect"), QMessageBox::ActionRole);
 ...
 messageBox.exec();
 if (messageBox.clickedButton() == disconnectButton) {
     ...
 }

This function was introduced in Qt 4.2.

See also standardButton() and button().

[override virtual protected] void QMessageBox::closeEvent(QCloseEvent *e)

Reimplements: QDialog::closeEvent(QCloseEvent *e).

[static] StandardButton QMessageBox::critical(QWidget *parent, const QString &title, const QString &text, StandardButtons buttons = Ok, StandardButton defaultButton = NoButton)

Opens a critical message box with the given title and text in front of the specified parent widget.

The standard buttons are added to the message box. defaultButton specifies the button used when Enter is pressed. defaultButton must refer to a button that was given in buttons. If defaultButton is QMessageBox::NoButton, QMessageBox chooses a suitable default automatically.

Returns the identity of the standard button that was clicked. If Esc was pressed instead, the escape button is returned.

The message box is an application modal dialog box.

This function was introduced in Qt 4.2.

See also question(), warning(), and information().

QPushButton *QMessageBox::defaultButton() const

Returns the button that should be the message box's default button. Returns nullptr if no default button was set.

This function was introduced in Qt 4.2.

See also setDefaultButton(), addButton(), and QPushButton::setDefault().

QAbstractButton *QMessageBox::escapeButton() const

Returns the button that is activated when escape is pressed.

By default, QMessageBox attempts to automatically detect an escape button as follows:

1. If there is only one button, it is made the escape button.
2. If there is a Cancel button, it is made the escape button.
3. On macOS only, if there is exactly one button with the role QMessageBox::RejectRole, it is made the escape button.

When an escape button could not be automatically detected, pressing Esc has no effect.

This function was introduced in Qt 4.2.

See also setEscapeButton() and addButton().

[override virtual protected] bool QMessageBox::event(QEvent *e)

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

[static] StandardButton QMessageBox::information(QWidget *parent, const QString &title, const QString &text, StandardButtons buttons = Ok, StandardButton defaultButton = NoButton)

Opens an information message box with the given title and text in front of the specified parent widget.

The standard buttons are added to the message box. defaultButton specifies the button used when Enter is pressed. defaultButton must refer to a button that was given in buttons. If defaultButton is QMessageBox::NoButton, QMessageBox chooses a suitable default automatically.

Returns the identity of the standard button that was clicked. If Esc was pressed instead, the escape button is returned.

The message box is an application modal dialog box.

This function was introduced in Qt 4.2.

See also question(), warning(), and critical().

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

Reimplements: QDialog::keyPressEvent(QKeyEvent *e).

void QMessageBox::open(QObject *receiver, const char *member)

Opens the dialog and connects its finished() or buttonClicked() signal to the slot specified by receiver and member. If the slot in member has a pointer for its first parameter the connection is to buttonClicked(), otherwise the connection is to finished().

The signal will be disconnected from the slot when the dialog is closed.

[static] StandardButton QMessageBox::question(QWidget *parent, const QString &title, const QString &text, StandardButtons buttons = StandardButtons(Yes | No), StandardButton defaultButton = NoButton)

Opens a question message box with the given title and text in front of the specified parent widget.

The standard buttons are added to the message box. defaultButton specifies the button used when Enter is pressed. defaultButton must refer to a button that was given in buttons. If defaultButton is QMessageBox::NoButton, QMessageBox chooses a suitable default automatically.

Returns the identity of the standard button that was clicked. If Esc was pressed instead, the escape button is returned.

The message box is an application modal dialog box.

This function was introduced in Qt 4.2.

See also information(), warning(), and critical().

void QMessageBox::removeButton(QAbstractButton *button)

Removes button from the button box without deleting it.

This function was introduced in Qt 4.2.

See also addButton() and setStandardButtons().

[override virtual protected] void QMessageBox::resizeEvent(QResizeEvent *event)

Reimplements: QDialog::resizeEvent(QResizeEvent *).

void QMessageBox::setCheckBox(QCheckBox *cb)

Sets the checkbox cb on the message dialog. The message box takes ownership of the checkbox. The argument cb can be nullptr to remove an existing checkbox from the message box.

This function was introduced in Qt 5.2.

See also checkBox().

void QMessageBox::setDefaultButton(QPushButton *button)

Sets the message box's default button to button.

This function was introduced in Qt 4.2.

See also defaultButton(), addButton(), and QPushButton::setDefault().

void QMessageBox::setDefaultButton(StandardButton button)

Sets the message box's default button to button.

This function was introduced in Qt 4.3.

See also addButton() and QPushButton::setDefault().

void QMessageBox::setEscapeButton(QAbstractButton *button)

Sets the button that gets activated when the Escape key is pressed to button.

This function was introduced in Qt 4.2.

See also escapeButton(), addButton(), and clickedButton().

void QMessageBox::setEscapeButton(StandardButton button)

Sets the buttons that gets activated when the Escape key is pressed to button.

This function was introduced in Qt 4.3.

See also addButton() and clickedButton().

void QMessageBox::setWindowModality(Qt::WindowModality windowModality)

This function shadows QWidget::setWindowModality().

Sets the modality of the message box to windowModality.

On macOS, if the modality is set to Qt::WindowModal and the message box has a parent, then the message box will be a Qt::Sheet, otherwise the message box will be a standard dialog.

This function was introduced in Qt 4.2.

void QMessageBox::setWindowTitle(const QString &title)

This function shadows QWidget::setWindowTitle().

Sets the title of the message box to title. On macOS, the window title is ignored (as required by the macOS Guidelines).

This function was introduced in Qt 4.2.

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

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

StandardButton QMessageBox::standardButton(QAbstractButton *button) const

Returns the standard button enum value corresponding to the given button, or NoButton if the given button isn't a standard button.

This function was introduced in Qt 4.2.

See also button() and standardButtons().

[static] StandardButton QMessageBox::warning(QWidget *parent, const QString &title, const QString &text, StandardButtons buttons = Ok, StandardButton defaultButton = NoButton)

Opens a warning message box with the given title and text in front of the specified parent widget.

The standard buttons are added to the message box. defaultButton specifies the button used when Enter is pressed. defaultButton must refer to a button that was given in buttons. If defaultButton is QMessageBox::NoButton, QMessageBox chooses a suitable default automatically.

Returns the identity of the standard button that was clicked. If Esc was pressed instead, the escape button is returned.

The message box is an application modal dialog box.

This function was introduced in Qt 4.2.

See also question(), information(), and critical().