qapplication.3qt

Trolltech公司发布的基于C++图形开发环境

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#endif
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    QApplication app(argc, argv, useGUI);
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    if ( useGUI ) {
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       //start GUI version
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       ...
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    } else {
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       //start non-GUI version
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       ...
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    }
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    return app.exec();
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  }
.fi
.SH "QApplication::QApplication ( int & argc, char ** argv, Type type )"
Constructs an application object with \fIargc\fR command line arguments in \fIargv\fR.
.PP
For Qt/Embedded, passing QApplication::GuiServer for \fItype\fR makes this application the server (equivalent to running with the -qws option).
.SH "QApplication::QApplication ( Display * dpy, HANDLE visual = 0, HANDLE colormap = 0 )"
Create an application, given an already open display \fIdpy\fR. If \fIvisual\fR and \fIcolormap\fR are non-zero, the application will use those as the default Visual and Colormap contexts.
.PP
\fBWarning:\fR Qt only supports TrueColor visuals at depths higher than 8 bits-per-pixel.
.PP
This is available only on X11.
.SH "QApplication::QApplication ( Display * dpy, int argc, char ** argv, HANDLE visual = 0, HANDLE colormap = 0 )"
Create an application, given an already open display \fIdpy\fR and using \fIargc\fR command line arguments in \fIargv\fR. If \fIvisual\fR and \fIcolormap\fR are non-zero, the application will use those as the default Visual and Colormap contexts.
.PP
\fBWarning:\fR Qt only supports TrueColor visuals at depths higher than 8 bits-per-pixel.
.PP
This is available only on X11.
.SH "QApplication::~QApplication ()\fC [virtual]\fR"
Cleans up any window system resources that were allocated by this application. Sets the global variable \fCqApp\fR to 0.
.SH "void QApplication::aboutQt ()\fC [slot]\fR"
Displays a simple message box about Qt. The message includes the version number of Qt being used by the application.
.PP
This is useful for inclusion in the Help menu of an application. See the examples/menu/menu.cpp example.
.PP
This function is a convenience slot for QMessageBox::aboutQt().
.SH "void QApplication::aboutToQuit ()\fC [signal]\fR"
This signal is emitted when the application is about to quit the main event loop, e.g. when the event loop level drops to zero. This may happen either after a call to quit() from inside the application or when the users shuts down the entire desktop session.
.PP
The signal is particularly useful if your application has to do some last-second cleanup. Note that no user interaction is possible in this state.
.PP
See also quit().
.SH "QWidget * QApplication::activeModalWidget ()\fC [static]\fR"
Returns the active modal widget.
.PP
A modal widget is a special top level widget which is a subclass of QDialog that specifies the modal parameter of the constructor as TRUE. A modal widget must be closed before the user can continue with other parts of the program.
.PP
Modal widgets are organized in a stack. This function returns the active modal widget at the top of the stack.
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See also activePopupWidget() and topLevelWidgets().
.SH "QWidget * QApplication::activePopupWidget ()\fC [static]\fR"
Returns the active popup widget.
.PP
A popup widget is a special top level widget that sets the WType_Popup widget flag, e.g. the QPopupMenu widget. When the application opens a popup widget, all events are sent to the popup. Normal widgets and modal widgets cannot be accessed before the popup widget is closed.
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Only other popup widgets may be opened when a popup widget is shown. The popup widgets are organized in a stack. This function returns the active popup widget at the top of the stack.
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See also activeModalWidget() and topLevelWidgets().
.SH "QWidget * QApplication::activeWindow () const"
Returns the application top-level window that has the keyboard input focus, or 0 if no application window has the focus. Note that there might be an activeWindow() even if there is no focusWidget(), for example if no widget in that window accepts key events.
.PP
See also QWidget::setFocus(), QWidget::focus, and focusWidget().
.PP
Example: network/mail/smtp.cpp.
.SH "void QApplication::addLibraryPath ( const QString & path )\fC [static]\fR"
Append \fIpath\fR to the end of the library path list. If \fIpath\fR is empty or already in the path list, the path list is not changed.
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The default path list consists of a single entry, the installation directory for plugins. The default installation directory for plugins is \fCINSTALL/plugins\fR, where \fCINSTALL\fR is the directory where Qt was installed.
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See also removeLibraryPath(), libraryPaths(), and setLibraryPaths().
.SH "QWidgetList * QApplication::allWidgets ()\fC [static]\fR"
Returns a list of all the widgets in the application.
.PP
The list is created using \fCnew\fR and must be deleted by the caller.
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The list is empty (QPtrList::isEmpty()) if there are no widgets.
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Note that some of the widgets may be hidden.
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Example that updates all widgets:
.PP
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    QWidgetList  *list = QApplication::allWidgets();
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    QWidgetListIt it( *list );         // iterate over the widgets
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    QWidget * w;
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    while ( (w=it.current()) != 0 ) {  // for each widget...
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        ++it;
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        w->update();
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    }
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    delete list;                      // delete the list, not the widgets
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.fi
.PP
The QWidgetList class is defined in the \fCqwidgetlist.h\fR header file.
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\fBWarning:\fR Delete the list as soon as you have finished using it. The widgets in the list may be deleted by someone else at any time.
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See also topLevelWidgets(), QWidget::visible, and QPtrList::isEmpty().
.SH "QString QApplication::applicationDirPath ()"
Returns the directory that contains the application executable.
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For example, if you have installed Qt in the \fCC:\Trolltech\Qt\fR directory, and you run the \fCdemo\fR example, this function will return "C:/Trolltech/Qt/examples/demo".
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On Mac OS X this will point to the directory actually containing the executable, which may be inside of an application bundle (if the application is bundled).
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\fBWarning:\fR On Unix, this function assumes that argv[0] contains the file name of the executable (which it normally does). It also assumes that the current directory hasn't been changed by the application.
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See also applicationFilePath().
.SH "QString QApplication::applicationFilePath ()"
Returns the file path of the application executable.
.PP
For example, if you have installed Qt in the \fCC:\Trolltech\Qt\fR directory, and you run the \fCdemo\fR example, this function will return "C:/Trolltech/Qt/examples/demo/demo.exe".
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\fBWarning:\fR On Unix, this function assumes that argv[0] contains the file name of the executable (which it normally does). It also assumes that the current directory hasn't been changed by the application.
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See also applicationDirPath().
.SH "int QApplication::argc () const"
Returns the number of command line arguments.
.PP
The documentation for argv() describes how to process command line arguments.
.PP
See also argv() and QApplication::QApplication().
.PP
Examples:
.)l chart/main.cpp and scribble/scribble.cpp.
.SH "char ** QApplication::argv () const"
Returns the command line argument vector.
.PP
\fCargv()[0]\fR is the program name, \fCargv()[1]\fR is the first argument and \fCargv()[argc()-1]\fR is the last argument.
.PP
A QApplication object is constructed by passing \fIargc\fR and \fIargv\fR from the \fCmain()\fR function. Some of the arguments may be recognized as Qt options and removed from the argument vector. For example, the X11 version of Qt knows about \fC-display\fR, \fC-font\fR and a few more options.
.PP
Example:
.PP
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        // showargs.cpp - displays program arguments in a list box
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        #include <qapplication.h>
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        #include <qlistbox.h>
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        int main( int argc, char **argv )
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        {
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            QApplication a( argc, argv );
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            QListBox b;
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            a.setMainWidget( &b );
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            for ( int i = 0; i < a.argc(); i++ )  // a.argc() == argc
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                b.insertItem( a.argv()[i] );      // a.argv()[i] == argv[i]
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            b.show();
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            return a.exec();
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        }
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.fi
.PP
If you run \fCshowargs -display unix:0 -font 9x15bold hello world\fR under X11, the list box contains the three strings "showargs"," hello" and "world".
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Qt provides a global pointer, \fCqApp\fR, that points to the QApplication object, and through which you can access argc() and argv() in functions other than main().
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See also argc() and QApplication::QApplication().
.PP
Examples:
.)l chart/main.cpp and scribble/scribble.cpp.
.SH "void QApplication::beep ()\fC [static]\fR"
Sounds the bell, using the default volume and sound.
.SH "QClipboard * QApplication::clipboard ()\fC [static]\fR"
Returns a pointer to the application global clipboard.
.PP
Examples:
.)l regexptester/regexptester.cpp and showimg/showimg.cpp.
.SH "void QApplication::closeAllWindows ()\fC [slot]\fR"
Closes all top-level windows.
.PP
This function is particularly useful for applications with many top-level windows. It could, for example, be connected to a "Quit" entry in the file menu as shown in the following code example:
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    // the "Quit" menu entry should try to close all windows
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    QPopupMenu* file = new QPopupMenu( this );
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    file->insertItem( "&Quit", qApp, SLOT(closeAllWindows()), CTRL+Key_Q );
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    // when the last window is closed, the application should quit
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    connect( qApp, SIGNAL( lastWindowClosed() ), qApp, SLOT( quit() ) );
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.fi
.PP
The windows are closed in random order, until one window does not accept the close event.
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See also QWidget::close(), QWidget::closeEvent(), lastWindowClosed(), quit(), topLevelWidgets(), and QWidget::isTopLevel.
.PP
Examples:
.)l action/application.cpp, application/application.cpp, helpviewer/helpwindow.cpp, mdi/application.cpp, and qwerty/qwerty.cpp.
.SH "bool QApplication::closingDown ()\fC [static]\fR"
Returns TRUE if the application objects are being destroyed; otherwise returns FALSE.
.PP
See also startingUp().
.SH "int QApplication::colorSpec ()\fC [static]\fR"
Returns the color specification.
.PP
See also QApplication::setColorSpec().
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Example: showimg/showimg.cpp.
.SH "void QApplication::commitData ( QSessionManager & sm )\fC [virtual]\fR"
This function deals with session management. It is invoked when the QSessionManager wants the application to commit all its data.
.PP
Usually this means saving all open files, after getting permission from the user. Furthermore you may want to provide a means by which the user can cancel the shutdown.
.PP
Note that you should not exit the application within this function. Instead, the session manager may or may not do this afterwards, depending on the context.
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\fBWarning:\fR Within this function, no user interaction is possible, \fIunless\fR you ask the session manager \fIsm\fR for explicit permission. See QSessionManager::allowsInteraction() and QSessionManager::allowsErrorInteraction() for details and example usage.
.PP
The default implementation requests interaction and sends a close event to all visible top level widgets. If any event was rejected, the shutdown is canceled.
.PP
See also isSessionRestored(), sessionId(), saveState(), and the Session Management overview.
.SH "int QApplication::cursorFlashTime ()\fC [static]\fR"
Returns the text cursor's flash (blink) time in milliseconds. The flash time is the time required to display, invert and restore the caret display.
.PP
The default value on X11 is 1000 milliseconds. On Windows, the control panel value is used.
.PP
Widgets should not cache this value since it may be changed at any time by the user changing the global desktop settings.
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See also setCursorFlashTime().
.SH "QTextCodec * QApplication::defaultCodec () const"
\fBThis function is obsolete.\fR It is provided to keep old source working. We strongly advise against using it in new code.
.PP
Returns QTextCodec::codecForTr().
.SH "QDesktopWidget * QApplication::desktop ()\fC [static]\fR"
Returns the desktop widget (also called the root window).
.PP
The desktop widget is useful for obtaining the size of the screen. It may also be possible to draw on the desktop. We recommend against assuming that it's possible to draw on the desktop, since this does not work on all operating systems.
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    QDesktopWidget *d = QApplication::desktop();
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    int w = d->width();     // returns desktop width
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    int h = d->height();    // returns desktop height
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.fi
.PP
Examples:
.)l canvas/main.cpp, helpviewer/main.cpp, i18n/main.cpp, qmag/qmag.cpp, qwerty/main.cpp, qwerty/qwerty.cpp, and scribble/main.cpp.
.SH "bool QApplication::desktopSettingsAware ()\fC [static]\fR"
Returns the value set by setDesktopSettingsAware(); by default TRUE.
.PP
See also setDesktopSettingsAware().
.SH "int QApplication::doubleClickInterval ()\fC [static]\fR"
Returns the maximum duration for a double click.
.PP
The default value on X11 is 400 milliseconds. On Windows, the control panel value is used.
.PP
See also setDoubleClickInterval().
.SH "int QApplication::enter_loop ()"
\fBThis function is obsolete.\fR It is provided to keep old source working. We strongly advise against using it in new code.
.PP