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QMessageBox Class Reference
[QtGui module]

The QMessageBox class provides a modal dialog for informing the user or for asking the user a question and receiving an answer. More...

Inherits QDialog.

Types

Methods

Static Methods

Qt Signals


Detailed Description

The QMessageBox class provides a modal dialog for informing the user or for asking the user a question and receiving an answer.

A message box displays a primary text to alert the user to a situation, an informative text to further explain the alert or to ask the user a question, and an optional detailed text to provide even more data if the user requests it. A message box can also display an icon and standard buttons for accepting a user response.

Two APIs for using QMessageBox are provided, the property-based API, and the static functions. Calling one of the static functions is the simpler approach, but it is less flexible than using the property-based API, and the result is less informative. Using the property-based API is recommended.

The Property-based API

To use the property-based API, construct an instance of QMessageBox, set the desired properties, and call exec_() to show the message. The simplest configuration is to set only the message text property.

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

The user must click the OK button to dismiss the message box. The rest of the GUI is blocked until the message box is dismissed.

A better approach than just alerting the user to an event is to also ask the user what to do about it. Store the question in the informative text property, and set the standard buttons property to the set of buttons you want as the set of user responses. The buttons are specified by combining values from StandardButtons using the bitwise OR operator. The display order for the buttons is platform-dependent. For example, on Windows, Save is displayed to the left of Cancel, whereas on Mac OS, the order is reversed.

Mark one of your standard buttons to be your default button.

 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_();

This is the approach recommended in the Mac OS X Guidelines. Similar guidelines apply for the other platforms, but note the different ways the informative text is handled for different platforms.

The exec_() slot returns the StandardButtons value of the button that was clicked.

 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;
 }

To give the user more information to help him answer the question, set the detailed text property. If the detailed text property is set, the Show Details... button will be shown.

Clicking the Show Details... button displays the detailed text.

Rich Text and the Text Format Property

The detailed text property is always interpreted as plain text. The main text and informative text properties can be either plain text or rich text. These strings are interpreted according to the setting of the text format property. The default setting is auto-text.

Note that for some plain text strings containing XML meta-characters, the auto-text rich text detection test may fail causing your plain text string to be interpreted incorrectly as rich text. In these rare cases, use Qt.convertFromPlainText() to convert your plain text string to a visually equivalent rich text string, or set the text format property explicitly with setTextFormat().

Severity Levels and the Icon and Pixmap Properties

QMessageBox supports four predefined message severity levels, or message types, which really only differ in the predefined icon they each show. Specify one of the four predefined message types by setting the icon property to one of the predefined icons. The following rules are guidelines:

Question For asking a question during normal operations.

Information For reporting information about normal operations.

Warning For reporting non-critical errors.

Critical For reporting critical errors.

Predefined icons are not defined by QMessageBox, but provided by the style. The default value is No Icon. The message boxes are otherwise the same for all cases. When using a standard icon, use the one recommended in the table, or use the one recommended by the style guidelines for your platform. If none of the standard icons is right for your message box, you can use a custom icon by setting the icon pixmap property instead of setting the icon property.

In summary, to set an icon, use either setIcon() for one of the standard icons, or setIconPixmap() for a custom icon.

The Static Functions API

Building message boxes with the static functions API, although convenient, is less flexible than using the property-based API, because the static function signatures lack parameters for setting the informative text and detailed text properties. One work-around for this has been to use the title parameter as the message box main text and the text parameter as the message box informative text. Because this has the obvious drawback of making a less readable message box, platform guidelines do not recommend it. The Microsoft Windows User Interface Guidelines recommend using the application name as the window's title, which means that if you have an informative text in addition to your main text, you must concatenate it to the text parameter.

Note that the static function signatures have changed with respect to their button parameters, which are now used to set the standard buttons and the default button.

Static functions are available for creating information(), question(), warning(), and critical() message boxes.

 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);

The Standard Dialogs example shows how to use QMessageBox and the other built-in Qt dialogs.

Advanced Usage

If the standard buttons are not flexible enough for your message box, you can use the addButton() overload that takes a text and a ButtonRoleto to add custom buttons. The ButtonRole is used by QMessageBox to determine the ordering of the buttons on screen (which varies according to the platform). You can test the value of clickedButton() after calling exec_(). For example,

 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
 }

Default and Escape Keys

The default button (i.e., the button activated when Enter is pressed) can be specified using setDefaultButton(). If a default button is not specified, QMessageBox tries to find one based on the button roles of the buttons used in the message box.

The escape button (the button activated when Esc is pressed) can be specified using setEscapeButton(). If an escape button is not specified, QMessageBox tries to find one using these rules:

  1. If there is only one button, it is the button activated when Esc is pressed.
  2. If there is a Cancel button, it is the button activated when Esc is pressed.
  3. If there is exactly one button having either the Reject role or the the No role, it is the button activated when Esc is pressed.

When an escape button can't be determined using these rules, pressing Esc has no effect.


Type Documentation

QMessageBox.ButtonRole

This enum describes the roles that can be used to describe buttons in the button box. Combinations of these roles are as flags used to describe different aspects of their behavior.

Constant Value Description
QMessageBox.InvalidRole -1 The button is invalid.
QMessageBox.AcceptRole 0 Clicking the button causes the dialog to be accepted (e.g. OK).
QMessageBox.RejectRole 1 Clicking the button causes the dialog to be rejected (e.g. Cancel).
QMessageBox.DestructiveRole 2 Clicking the button causes a destructive change (e.g. for Discarding Changes) and closes the dialog.
QMessageBox.ActionRole 3 Clicking the button causes changes to the elements within the dialog.
QMessageBox.HelpRole 4 The button can be clicked to request help.
QMessageBox.YesRole 5 The button is a "Yes"-like button.
QMessageBox.NoRole 6 The button is a "No"-like button.
QMessageBox.ApplyRole 8 The button applies current changes.
QMessageBox.ResetRole 7 The button resets the dialog's fields to default values.

See also StandardButton.

QMessageBox.Icon

This enum has the following values:

Constant Value Description
QMessageBox.NoIcon 0 the message box does not have any icon.
QMessageBox.Question 4 an icon indicating that the message is asking a question.
QMessageBox.Information 1 an icon indicating that the message is nothing out of the ordinary.
QMessageBox.Warning 2 an icon indicating that the message is a warning, but can be dealt with.
QMessageBox.Critical 3 an icon indicating that the message represents a critical problem.

QMessageBox.StandardButton

These enums describe flags for standard buttons. Each button has a defined ButtonRole.

Constant Value Description
QMessageBox.Ok 0x00000400 An "OK" button defined with the AcceptRole.
QMessageBox.Open 0x00002000 A "Open" button defined with the AcceptRole.
QMessageBox.Save 0x00000800 A "Save" button defined with the AcceptRole.
QMessageBox.Cancel 0x00400000 A "Cancel" button defined with the RejectRole.
QMessageBox.Close 0x00200000 A "Close" button defined with the RejectRole.
QMessageBox.Discard 0x00800000 A "Discard" or "Don't Save" button, depending on the platform, defined with the DestructiveRole.
QMessageBox.Apply 0x02000000 An "Apply" button defined with the ApplyRole.
QMessageBox.Reset 0x04000000 A "Reset" button defined with the ResetRole.
QMessageBox.RestoreDefaults 0x08000000 A "Restore Defaults" button defined with the ResetRole.
QMessageBox.Help 0x01000000 A "Help" button defined with the HelpRole.
QMessageBox.SaveAll 0x00001000 A "Save All" button defined with the AcceptRole.
QMessageBox.Yes 0x00004000 A "Yes" button defined with the YesRole.
QMessageBox.YesToAll 0x00008000 A "Yes to All" button defined with the YesRole.
QMessageBox.No 0x00010000 A "No" button defined with the NoRole.
QMessageBox.NoToAll 0x00020000 A "No to All" button defined with the NoRole.
QMessageBox.Abort 0x00040000 An "Abort" button defined with the RejectRole.
QMessageBox.Retry 0x00080000 A "Retry" button defined with the AcceptRole.
QMessageBox.Ignore 0x00100000 An "Ignore" button defined with the AcceptRole.
QMessageBox.NoButton 0x00000000 An invalid button.

The following values are obsolete:

Constant Value Description
QMessageBox.YesAll YesToAll Use YesToAll instead.
QMessageBox.NoAll NoToAll Use NoToAll instead.
QMessageBox.Default 0x00000100 Use the defaultButton argument of information(), warning(), etc. instead, or call setDefaultButton().
QMessageBox.Escape 0x00000200 Call setEscapeButton() instead.
QMessageBox.FlagMask 0x00000300  
QMessageBox.ButtonMask ~FlagMask  

This enum was introduced or modified in Qt 4.2.

The StandardButtons type is a typedef for QFlags<StandardButton>. It stores an OR combination of StandardButton values.

See also ButtonRole and standardButtons.


Method Documentation

QMessageBox.__init__ (self, QWidget parent = None)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

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.__init__ (self, Icon icon, QString title, QString text, StandardButtons buttons = QMessageBox.NoButton, QWidget parent = None, Qt.WindowFlags flags = Qt.Dialog|Qt.MSWindowsFixedSizeDialogHint)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

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 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.__init__ (self, QString title, QString text, Icon icon, int button0, int button1, int button2, QWidget parent = None, Qt.WindowFlags flags = Qt.Dialog|Qt.MSWindowsFixedSizeDialogHint)

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

QMessageBox.about (QWidget parent, QString caption, 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 Mac OS X, 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().

QMessageBox.aboutQt (QWidget parent, QString title = QString())

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 application modal.

See also QApplication.aboutQt().

QMessageBox.addButton (self, QAbstractButton button, ButtonRole role)

The button argument has it's ownership transferred to Qt.

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 (self, 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 (self, 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 (self, StandardButton which)

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().

ButtonRole QMessageBox.buttonRole (self, QAbstractButton button)

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().

list-of-QAbstractButton QMessageBox.buttons (self)

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().

QString QMessageBox.buttonText (self, int button)

QMessageBox.changeEvent (self, QEvent)

Reimplemented from QWidget.changeEvent().

QAbstractButton QMessageBox.clickedButton (self)

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().

QMessageBox.closeEvent (self, QCloseEvent)

Reimplemented from QWidget.closeEvent().

StandardButton QMessageBox.critical (QWidget parent, QString title, QString text, StandardButtons buttons = QMessageBox.Ok, StandardButton defaultButton = QMessageBox.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.

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().

int QMessageBox.critical (QWidget parent, QString title, QString text, int button0, int button1, int button2 = 0)

int QMessageBox.critical (QWidget parent, QString title, QString text, QString button0Text, QString button1Text = QString(), QString button2Text = QString(), int defaultButtonNumber = 0, int escapeButtonNumber = -1)

QPushButton QMessageBox.defaultButton (self)

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().

QString QMessageBox.detailedText (self)

QAbstractButton QMessageBox.escapeButton (self)

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 (self, QEvent e)

Reimplemented from QObject.event().

Icon QMessageBox.icon (self)

QPixmap QMessageBox.iconPixmap (self)

StandardButton QMessageBox.information (QWidget parent, QString title, QString text, StandardButtons buttons = QMessageBox.Ok, StandardButton defaultButton = QMessageBox.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.

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 critical().

int QMessageBox.information (QWidget parent, QString title, QString text, int button0, int button1 = 0, int button2 = 0)

int QMessageBox.information (QWidget parent, QString title, QString text, QString button0Text, QString button1Text = QString(), QString button2Text = QString(), int defaultButtonNumber = 0, int escapeButtonNumber = -1)

QString QMessageBox.informativeText (self)

QMessageBox.keyPressEvent (self, QKeyEvent)

Reimplemented from QWidget.keyPressEvent().

QMessageBox.open (self)

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.

QMessageBox.open (self, QObject receiver, SLOT()SLOT() member)

QMessageBox.open (self, callable receiver)

StandardButton QMessageBox.question (QWidget parent, QString title, QString text, StandardButtons buttons = QMessageBox.Ok, StandardButton defaultButton = QMessageBox.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.

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

int QMessageBox.question (QWidget parent, QString title, QString text, int button0, int button1 = 0, int button2 = 0)

int QMessageBox.question (QWidget parent, QString title, QString text, QString button0Text, QString button1Text = QString(), QString button2Text = QString(), int defaultButtonNumber = 0, int escapeButtonNumber = -1)

QMessageBox.removeButton (self, QAbstractButton button)

The button argument

Removes button from the button box without deleting it.

This function was introduced in Qt 4.2.

See also addButton() and setStandardButtons().

QMessageBox.resizeEvent (self, QResizeEvent)

Reimplemented from QWidget.resizeEvent().

QMessageBox.setButtonText (self, int button, QString)

QMessageBox.setDefaultButton (self, 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().

QMessageBox.setDefaultButton (self, 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().

QMessageBox.setDetailedText (self, QString text)

QMessageBox.setEscapeButton (self, 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().

QMessageBox.setEscapeButton (self, 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().

QMessageBox.setIcon (self, Icon)

QMessageBox.setIconPixmap (self, QPixmap)

QMessageBox.setInformativeText (self, QString text)

QMessageBox.setStandardButtons (self, StandardButtons buttons)

QMessageBox.setText (self, QString)

QMessageBox.setTextFormat (self, Qt.TextFormat)

QMessageBox.setWindowModality (self, 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.

QMessageBox.setWindowTitle (self, 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.

QMessageBox.showEvent (self, QShowEvent)

Reimplemented from QWidget.showEvent().

QSize QMessageBox.sizeHint (self)

StandardButton QMessageBox.standardButton (self, QAbstractButton button)

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().

StandardButtons QMessageBox.standardButtons (self)

QPixmap QMessageBox.standardIcon (Icon icon)

QString QMessageBox.text (self)

Qt.TextFormat QMessageBox.textFormat (self)

StandardButton QMessageBox.warning (QWidget parent, QString title, QString text, StandardButtons buttons = QMessageBox.Ok, StandardButton defaultButton = QMessageBox.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.

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(), information(), and critical().

int QMessageBox.warning (QWidget parent, QString title, QString text, int button0, int button1, int button2 = 0)

int QMessageBox.warning (QWidget parent, QString title, QString text, QString button0Text, QString button1Text = QString(), QString button2Text = QString(), int defaultButtonNumber = 0, int escapeButtonNumber = -1)


Qt Signal Documentation

void buttonClicked (QAbstractButton*)

This is the default overload of this signal.

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


PyQt 4.11.1 for X11Copyright © Riverbank Computing Ltd and Digia 2014Qt 4.8.6