QMessageBox(3qt)

NAME
QMessageBox - Displays a brief message, an icon, and some buttons

SYNOPSIS

#include <qmessagebox.h>

Inherits QDialog.

  Public Members
enum Icon { NoIcon = 0, Information = 1, Warning = 2, Critical = 3 }
QMessageBox ( QWidget * parent=0, const char * name=0 )
QMessageBox ( const char * caption, const char * text, Icon icon, int button0, int button1, int button2, QWidget * parent=0, const char * name=0, bool modal=TRUE, WFlags f=0 )
~QMessageBox ()
enum { Ok = 1, Cancel = 2, Yes = 3, No = 4, Abort = 5, Retry = 6, Ignore = 7, ButtonMask = 0x07, Default = 0x100, Escape = 0x200, FlagMask = 0x300 }
const char* text () const
void setText ( const char * )
Icon icon () const
void setIcon ( Icon )
const QPixmap* iconPixmap () const
void setIconPixmap ( const QPixmap & )
const char* buttonText ( int button ) const
void setButtonText ( int button, const char * )
virtual void adjustSize ()
virtual void setStyle ( GUIStyle )

  Static Public Members
int information ( QWidget * parent, const char * caption, const char * text, int button0, int button1=0, int button2=0 )
int information ( QWidget * parent, const char * caption, const char * text, const char * button0Text = "OK", const char * button1Text = 0, const char * button2Text = 0, int defaultButtonNumber = 0, int escapeButtonNumber = -1 )
int warning ( QWidget * parent, const char * caption, const char * text, int button0, int button1, int button2=0 )
int warning ( QWidget * parent, const char * caption, const char * text, const char * button0Text = "OK", const char * button1Text = 0, const char * button2Text = 0, int defaultButtonNumber = 0, int escapeButtonNumber = -1 )
int critical ( QWidget * parent, const char * caption, const char * text, int button0, int button1, int button2=0 )
int critical ( QWidget * parent, const char * caption, const char * text, const char * button0Text = "OK", const char * button1Text = 0, const char * button2Text = 0, int defaultButtonNumber = 0, int escapeButtonNumber = -1 )
void about ( QWidget * parent, const char * caption, const char * text )
void aboutQt ( QWidget * parent, const char * caption=0 )
QPixmap standardIcon ( Icon icon, GUIStyle style )

  Protected Members
virtual void resizeEvent ( QResizeEvent * )
virtual void keyPressEvent ( QKeyEvent * )

DESCRIPTION
Displays a brief message, an icon, and some buttons.

A message box is a modal dialog that displays an icon, a text and up to three push buttons. It's used for simple messages and questions.

QMessageBox provides a range of different messages, arranged roughly along two axes: Severity and complexity.

Severity is

Information - for message boxes that are part of normal operation,

Warning - for message boxes that tell the user about errors or ask the user how to fix an error, or

Critical - as Warning, but for critical errors. The message box has a different icon for each of the severity levels.

Complexity is one button (Ok, sometimes Dismiss for Motif applications) for a simple messages, or two or even three buttons for questions.

Here are some examples of how to use the static member functions. After these examples you will find an overview of the non-static member functions.

If a program is unable to find a supporting file, it may perhaps do:

    QMessageBox::information( this, "Application name here",
                              "Unable to find the file \"index.html\".\n"
                              "The factory default will be used instead." );

The Microsoft Windows User Interface Guidelines strongly recommends using the application name as window caption. The message box has just one button, OK, and its text tells the user both what happened and what the program will do about it. Since the application is able to make do, the message box is just information, not a warning or a critical error.

Exiting a program is part of its normal operation, and if there are unsaved data the user probably should be asked what to do, for example like this:

    switch( QMessageBox::information( this, "Application name here",
                                      "The document contains unsaved work\n"
                                      "Do you want to save it before exiting?",
                                      "&Save", "&Don't Save", "&Cancel",
                                      0,      // Enter == button 0
                                      2 ) ) { // Escape == button 2
    case 0: // Save clicked, Alt-S or Enter pressed.
        // save
        break;
    case 1: // Don't Save clicked or Alt-D pressed
        // don't save but exit
        break;
    case 2: // Cancel clicked, Alt-C or Escape pressed
        // don't exit
        break;
    }

Again, the application name is used as window caption, as Microsoft recommends. The Escape button cancels the entire Exit operation, and Enter/Return saves the document and exits.

warning() can be used to tell the user about unusual errors, or errors which can't be easily fixed:

    switch( QMessageBox::warning( this, "Application name here",
                                  "Could not connect to the <mumble> server.\n"
                                  "This program can't function correctly "
                                  "without the server.\n\n",
                                  "Try again", "Quit", 0,
                                  0, 1 );
    case 0: // Try again or Enter
        // try again
        break;
    case 1: // Quit or Escape
        // exit
        break;
    }

Disk full errors are unusual (in a perfect world, they are) and they certainly can be hard to correct. This example uses predefined buttons instead of hardcoded button texts:

    switch( QMessageBox::warning( this, "Application name here",
                                  "Could not save the the user preferences,\n"
                                  "because the disk is full.  You can delete\n"
                                  "some files and press Retry, or you can\n"
                                  "abort the Save Preferences operation.",
                                  QMessageBox::Retry | QMessageBox::Default,
                                  QMessageBox::Abort | QMessageBox::Escape )) {
    case QMessageBox::Retry: // Retry or Enter
        // try again
        break;
    case QMessageBox::Abort: // Abort or Cancel
        // abort
        break;
    }

The critical() function should be reserved for critical errors. In this example, errorDetails is a QString or const char *, and QString is used to concatenate several strings:

    QMessageBox::critical( 0, "Application name here",
                           QString("An internal error occured. Please call ") +
                           "technical support at 123456789 and report these\n"+
                           "numbers:\n\n" + errorDetails +
                           "\n\n<Application> will now exit." );

QMessageBox provides a very simple About box, which displays an appropriate icon and the string you give it:

     QMessageBox::about( this, "About <Application>",
                         "<Application> is a <one-paragraph blurb>\n\n"
                         "Copyright 1951-1997 Such-and-such.  "
                         "<License words here.>\n\n"
                         "For technical support, call 123456789 or see\n"
                         "http://www.such-and-such.com/Application/\n" );

See about() for more information.

Finally, you can make a QMessageBox from scratch and set custom button texts:

    QMessageBox mb( "Application name here",
                    "Saving the file will overwrite the old file on disk.\n"
                    "Do you really want to save?",
                    QMessageBox::Information,
                    QMessageBox::Yes | QMessageBox::Default,
                    QMessageBox::No,
                    QMessageBox::Cancel | QMessageBox::Escape );
    mb.setButtonText( QMessageBox::Yes, "Save" );
    mb.setButtonText( QMessageBox::No, "Don't Save" );
    switch( mb.exec() ) {
        case QMessageBox::Yes:
            // save and exit
            break;
        case QMessageBox::No:
            // exit without saving
            break;
        case QMessageBox::Cancel:
            // don't save and don't exit
            break;
    }

QMessageBox defines two enum types, Icon and an unnamed button type. Icon defines the Information, Warning and Critical icons for each GUI style. It is used by the constructor, by the static member functions information(), warning() and critical(), and there is a function called standardIcon() which gives you access to the various icons.

The button types are:

Ok - the default for single-button message boxes

Cancel - note that this is not automatically Escape

Yes

No

Abort

Retry

Ignore

Button types can be combined with two modifiers by using OR:

Default - makes pressing Enter or Return be equivalent with clicking this button. Normally used with Ok, Yes or similar.

Escape - makes pressing Escape be equivalent with this button. Normally used with Abort, Cancel or similar.

The text(), icon() and iconPixmap() functions provide access to the current text and pixmap of a message box, and setText(), setIcon() and setIconPixmap() lets you change it. The difference between setIcon() and setIconPixmap() is that the former accepts a QMessageBox::Icon and can it be used to set standard icons while the latter accepts a QPixmap and can be used to set custom icons.

setButtonText() and buttonText() provide access to the buttons.

QMessageBox has no signals or slots.

[Image Omitted]

[Image Omitted]

See also: QDialog, Isys on error messages, and GUI Design Handbook: Message Box.

Examples: showimg/showimg.cpp

MEMBER FUNCTION DOCUMENTATION

QMessageBox::QMessageBox ( QWidget * parent=0, const char * name=0 )
Constructs a message box with no text and a button with the text "OK".

If parent is 0, then the message box becomes an application-global modal dialog box. If parent is a widget, the message box becomes modal relative to parent.

The parent and name arguments are passed to the QDialog constructor.

QMessageBox::QMessageBox ( const char * caption, const char * text, Icon icon, int button0, int button1, int button2, QWidget * parent=0, const char * name=0, bool modal=TRUE, WFlags f=0 )
Constructs a message box with a caption, a text, an icon and up to three buttons.

The icon must be one of:

QMessageBox::NoIcon

QMessageBox::Information

QMessageBox::Warning

QMessageBox::Critical

Each button can have one of the following values:

QMessageBox::Ok

QMessageBox::Cancel

QMessageBox::Yes

QMessageBox::No

QMessageBox::Abort

QMessageBox::Retry

QMessageBox::Ignore

One of the buttons can be combined with the QMessageBox::Default flag to make a default button.

One of the buttons can be combined with the QMessageBox::Escape flag to make an escape option. Hitting the Esc key on the keyboard has the same effect as clicking this button with the mouse.

Example:

    QMessageBox mb( "Hardware failure",
                    "Disk error detected\nDo you want to stop?",
                    QMessageBox::NoIcon,
                    QMessageBox::Yes | QMessageBox::Default,
                    QMessageBox::No | QMessageBox::Escape );
    if ( mb.exec() == QMessageBox::No )
        // try again

If parent is 0, then the message box becomes an application-global modal dialog box. If parent is a widget, the message box becomes modal relative to parent.

If modal is TRUE the message becomes modal, otherwise it becomes modeless.

The parent, name, modal and f arguments are passed to the QDialog constructor.

See also: setCaption(), setText() and setIcon().

QMessageBox::~QMessageBox ()
Destroys the message box.

void QMessageBox::about ( QWidget * parent, const char * caption, const char * text ) [static]
Displays a simple about box with window caption caption and body text text.

about() looks for a suitable icon for the box 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 too fails, it tries the main widget.

4   As a last resort it uses the Information icon.

The about box has a single button labelled OK.

See also: QWidget::icon() and QApplication::mainWidget().

Examples: menu/menu.cpp

void QMessageBox::aboutQt ( QWidget * parent, const char * caption=0 ) [static]
Displays a simple message box about Qt, with window caption caption and optionally centered over parent.

This is neat for inclusion into the Help menu. See the menu.cpp example.

Examples: trivial/trivial.cpp menu/menu.cpp

void QMessageBox::adjustSize () [virtual]
Adjusts the size of the message box to fit the contents just before QDialog::exec() or QDialog::show() is called.

This function will not be called if the message box has been explicitly resized before showing it.

Reimplemented from QWidget.

const char * QMessageBox::buttonText ( int button ) const
Returns the text of the message box button button, or null if the message box does not contain the button.

Example:

    QMessageBox mb( QMessageBox::Ok, QMessageBox::Cancel, 0 );
    mb.buttonText( QMessageBox::Cancel );  // returns "Cancel"
    mb.buttonText( QMessageBox::Ignore );  // returns 0

See also: setButtonText().

int QMessageBox::critical ( QWidget * parent, const char * caption, const char * text, const char * button0Text = OK", const char * button1Text = 0, const char * button2Text = 0, int defaultButtonNumber = 0, int escapeButtonNumber = -1 ) [static]"
Displays a critical error message box with a caption, a text and 1-3 buttons. Returns the number of the button that was clicked (0, 1 or 2).

button0Text is the text of the first button and must be present, button1Text is the text of the second button and is optional, and button2Text is the text of the third button and is optional. defaultbuttonNumber (0-2) is the index of the default button; pressing Return or Enter is the same as clicking the default button. It defaults to 0 (the first button). escapeButtonNumber is the index of the Escape button; pressing Escape is the same as clicking this button. It defaults to -1 (pressing Escape does nothing); supply 0, 1 or 2 to make pressing Escape be equivalent with clicking the relevant button.

If parent is 0, then the message box becomes an application-global modal dialog box. If parent is a widget, the message box becomes modal relative to parent.

See also: information() and warning().

int QMessageBox::critical ( QWidget * parent, const char * caption, const char * text, int button0, int button1, int button2=0 ) [static]
Opens a critical message box with a caption, a text and up to three buttons. Returns the identifier of the button that was clicked.

If parent is 0, then the message box becomes an application-global modal dialog box. If parent is a widget, the message box becomes modal relative to parent.

See also: information() and warning().

QMessageBox::Icon QMessageBox::icon() const
Returns the icon of the message box.

The return value is one of the following:

QMessageBox::NoIcon

QMessageBox::Information

QMessageBox::Warning

QMessageBox::Critical

See also: setIcon() and iconPixmap().

const QPixmap * QMessageBox::iconPixmap () const
Returns the icon pixmap of the message box.

Example:

    QMessageBox mb(...);
    mb.setIcon( QMessageBox::Warning );
    mb.iconPixmap();    // returns the warning icon pixmap

See also: setIconPixmap() and icon().

int QMessageBox::information ( QWidget * parent, const char * caption, const char * text, const char * button0Text = OK", const char * button1Text = 0, const char * button2Text = 0, int defaultButtonNumber = 0, int escapeButtonNumber = -1 ) [static]"
Displays an information message box with a caption, a text and 1-3 buttons. Returns the number of the button that was clicked (0, 1 or 2).

button0Text is the text of the first button and must be present, button1Text is the text of the second button and is optional, and button2Text is the text of the third button and is optional. defaultbuttonNumber (0-2) is the index of the default button; pressing Return or Enter is the same as clicking the default button. It defaults to 0 (the first button). escapeButtonNumber is the index of the Escape button; pressing Escape is the same as clicking this button. It defaults to -1 (pressing Escape does nothing); supply 0, 1 or 2 to make pressing Escape be equivalent with clicking the relevant button.

If parent is 0, then the message box becomes an application-global modal dialog box. If parent is a widget, the message box becomes modal relative to parent.

See also: warning() and critical().

int QMessageBox::information ( QWidget * parent, const char * caption, const char * text, int button0, int button1=0, int button2=0 ) [static]
Opens an information message box with a caption, a text and up to three buttons. Returns the identifier of the button that was clicked.

If parent is 0, then the message box becomes an application-global modal dialog box. If parent is a widget, the message box becomes modal relative to parent.

See also: warning() and critical().

Examples: picture/picture.cpp widgets/widgets.cpp

void QMessageBox::keyPressEvent ( QKeyEvent * e ) [virtual protected]
Handles key press events for the message box.

Reimplemented from QWidget.

void QMessageBox::resizeEvent ( QResizeEvent * ) [virtual protected]
Handles resize events for the message box.

Reimplemented from QWidget.

void QMessageBox::setButtonText ( int button, const char * text )
Sets the text of the message box button button to text. Setting the text of a button that is not in the message box is quietly ignored.

Example:

    QMessageBox mb( QMessageBox::Ok, QMessageBox::Cancel, 0 );
    mb.setButtonText( QMessageBox::Ok, "All Right" );
    mb.setButtonText( QMessageBox::Yes, "Yo" );   // ignored

See also: buttonText().

void QMessageBox::setIcon ( Icon icon )
Sets the icon of the message box to icon, which is a predefined icon:

QMessageBox::NoIcon

QMessageBox::Information

QMessageBox::Warning

QMessageBox::Critical

The actual pixmap used for displaying the icon depends on the current GUI style. You can also set a custom pixmap icon using the setIconPixmap() function.

See also: icon(), setIconPixmap() and iconPixmap().

void QMessageBox::setIconPixmap ( const QPixmap & pixmap )
Sets the icon of the message box to a custom pixmap. Note that it's often hard to draw one pixmap which looks appropriate in both Motif and Windoes GUI styles. You may want to draw two.

See also: iconPixmap() and setIcon().

void QMessageBox::setStyle ( GUIStyle s ) [virtual]
Reimplemented for implementational reasons.

Reimplemented from QWidget.

void QMessageBox::setText ( const char * text )
Sets the message box text to be displayed.

See also: text().

QPixmap QMessageBox::standardIcon ( Icon icon, GUIStyle style ) [static]
Returns the pixmap used for a standard icon. This allows the pixmaps to be used in more complex message boxes.

const char * QMessageBox::text () const
Returns the message box text currently set, or null if no text has been set.

See also: setText().

int QMessageBox::warning ( QWidget * parent, const char * caption, const char * text, const char * button0Text = OK", const char * button1Text = 0, const char * button2Text = 0, int defaultButtonNumber = 0, int escapeButtonNumber = -1 ) [static]"
Displays a warning message box with a caption, a text and 1-3 buttons. Returns the number of the button that was clicked (0, 1 or 2).

button0Text is the text of the first button and must be present, button1Text is the text of the second button and is optional, and button2Text is the text of the third button and is optional. defaultbuttonNumber (0-2) is the index of the default button; pressing Return or Enter is the same as clicking the default button. It defaults to 0 (the first button). escapeButtonNumber is the index of the Escape button; pressing Escape is the same as clicking this button. It defaults to -1 (pressing Escape does nothing); supply 0, 1 or 2 to make pressing Escape be equivalent with clicking the relevant button.

If parent is 0, then the message box becomes an application-global modal dialog box. If parent is a widget, the message box becomes modal relative to parent.

See also: information() and critical().

int QMessageBox::warning ( QWidget * parent, const char * caption, const char * text, int button0, int button1, int button2=0 ) [static]
Opens a warning message box with a caption, a text and up to three buttons. Returns the identifier of the button that was clicked.

If parent is 0, then the message box becomes an application-global modal dialog box. If parent is a widget, the message box becomes modal relative to parent.

See also: information() and critical().

Examples: showimg/showimg.cpp

SEE ALSO
http://www.troll.no/qt/qmessagebox.html

COPYRIGHT
Copyright 1992-1997 Troll Tech AS. See the LICENSE file included in the distribution for a complete license statement.

AUTHOR
Generated automatically from the source code.