QMessageBox Class Reference

 #include <QMessageBox>

 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 ( QWidget * parent = 0 )

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

On Mac OS X, 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.

QMessageBox::QMessageBox ( Icon icon, const QString & title, const QString & text, StandardButtons buttons = NoButton, QWidget * parent = 0, 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.

If parent is 0, the message box is an application modal dialog box. If parent is a widget, the message box is window modal relative to parent.

On Mac OS X, if parent is not 0 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 ()

Destroys the message box.

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

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 Mac OS X, the about box is popped up as a modeless window; on other platforms, it is currently a window modal.

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

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

Displays a simple message box about Qt, with the given title and centered over parent (if parent is not 0). 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 Mac OS X, the about box is popped up as a modeless window; on other platforms, it is currently window 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 0 if the standard button doesn't exist in this message box.

This function was introduced in Qt 4.2.

See also standardButtons and standardButton().

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

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

ButtonRole QMessageBox::buttonRole ( QAbstractButton * button ) const

Returns the button role for the specified button. This function returns InvalidRole if button is 0 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().

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

Reimplemented from QWidget::changeEvent().

QAbstractButton * QMessageBox::clickedButton () const

Returns the button that was clicked by the user, or 0 if the user hit the Esc key and no escape button was set.

If exec() hasn't been called yet, returns 0.

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().

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

Reimplemented from QWidget::closeEvent().

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

Opens a critical message box with the specified title and text. 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.

If parent is 0, the message box is an application modal dialog box. If parent is a widget, the message box is window modal relative to parent.

Warning: Do not delete parent during the execution of the dialog. If you want to do this, you should create the dialog yourself using one of the QMessageBox constructors.

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 0 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 Mac OS X 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().

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

Reimplemented from QObject::event().

int QMessageBox::exec () [slot]

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

When using a QMessageBox with standard buttons, this functions 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().

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

Opens an information message box with the specified title and text. 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.

If parent is 0, the message box is an application modal dialog box. If parent is a widget, the message box is window modal relative to parent.

This function was introduced in Qt 4.2.

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

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

Reimplemented from QWidget::keyPressEvent().

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

This is an overloaded function.

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.

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

Opens a question message box with the specified title and text. 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.

If parent is 0, the message box is an application modal dialog box. If parent is a widget, the message box is window modal relative to parent.

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().

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

Reimplemented from QWidget::resizeEvent().

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::setVisible ( bool visible ) [virtual]

Reimplemented from QWidget::setVisible().

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

This function shadows QWidget::setWindowModality().

Sets the modality of the message box to windowModality.

On Mac OS X, 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 Mac OS X, the window title is ignored (as required by the Mac OS X Guidelines).

This function was introduced in Qt 4.2.

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

Reimplemented from QWidget::showEvent().

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().

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

Opens a warning message box with the specified title and text. 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.

If parent is 0, the message box is an application modal dialog box. If parent is a widget, the message box is window modal relative to parent.

This function was introduced in Qt 4.2.

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