| 1 | /****************************************************************************
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| 2 | **
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| 3 | ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
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| 4 | ** All rights reserved.
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| 5 | ** Contact: Nokia Corporation ([email protected])
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| 6 | **
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| 7 | ** This file is part of the documentation of the Qt Toolkit.
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| 8 | **
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| 9 | ** $QT_BEGIN_LICENSE:FDL$
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| 10 | ** Commercial Usage
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| 11 | ** Licensees holding valid Qt Commercial licenses may use this file in
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| 12 | ** accordance with the Qt Commercial License Agreement provided with the
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| 13 | ** Software or, alternatively, in accordance with the terms contained in a
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| 14 | ** written agreement between you and Nokia.
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| 15 | **
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| 16 | ** GNU Free Documentation License
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| 17 | ** Alternatively, this file may be used under the terms of the GNU Free
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| 18 | ** Documentation License version 1.3 as published by the Free Software
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| 19 | ** Foundation and appearing in the file included in the packaging of this
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| 20 | ** file.
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| 21 | **
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| 22 | ** If you have questions regarding the use of this file, please contact
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| 23 | ** Nokia at [email protected].
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| 24 | ** $QT_END_LICENSE$
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| 25 | **
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| 26 | ****************************************************************************/
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| 27 |
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| 28 | /*!
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| 29 | \page gettingstartedqt.html
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| 30 |
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| 31 | \title Getting Started Programming with Qt
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| 32 | \ingroup gettingStarted
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| 33 |
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| 34 | Welcome to the world of Qt--the cross-platform GUI toolkit. In
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| 35 | this getting started guide, we teach basic Qt knowledge by
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| 36 | implementing a simple Notepad application. After reading this
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| 37 | guide, you should be ready to delve into our overviews and API
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| 38 | documentation, and find the information you need for the
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| 39 | application you are developing.
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| 40 |
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| 41 | \section1 Hello Notepad
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| 42 |
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| 43 | In this first example, we simply create and show a text edit in a
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| 44 | window frame on the desktop. This represents the simplest possible
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| 45 | Qt program that has a GUI.
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| 46 |
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| 47 | \image gs1.png
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| 48 |
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| 49 | Here is the code:
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| 50 |
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| 51 | \code
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| 52 | 1 #include <QApplication>
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| 53 | 2 #include <QTextEdit>
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| 54 | 3
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| 55 | 4 int main(int argv, char **args)
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| 56 | 5 {
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| 57 | 6 QApplication app(argv, args);
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| 58 | 7
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| 59 | 8 QTextEdit textEdit;
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| 60 | 9 textEdit.show();
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| 61 | 10
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| 62 | 11 return app.exec();
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| 63 | 12 }
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| 64 | \endcode
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| 65 |
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| 66 | Let us go through the code line by line. In the first two lines, we
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| 67 | include the header files for QApplication and QTextEdit, which are
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| 68 | the two classes that we need for this example. All Qt classes have
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| 69 | a header file named after them.
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| 70 |
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| 71 | Line 6 creates a QApplication object. This object manages
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| 72 | application-wide resources and is necessary to run any Qt program
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| 73 | that has a GUI. It needs \c argv and \c args because Qt accepts a
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| 74 | few command line arguments.
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| 75 |
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| 76 | Line 8 creates a QTextEdit object. A text edit is a visual element
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| 77 | in the GUI. In Qt, we call such elements widgets. Examples of
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| 78 | other widgets are scroll bars, labels, and radio buttons. A widget
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| 79 | can also be a container for other widgets; a dialog or a main
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| 80 | application window, for example.
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| 81 |
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| 82 | Line 9 shows the text edit on the screen in its own window frame.
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| 83 | Since widgets also function as containers (for instance a
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| 84 | QMainWindow, which has toolbars, menus, a status bar, and a few
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| 85 | other widgets), it is possible to show a single widget in its own
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| 86 | window. Widgets are not visible by default; the function
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| 87 | \l{QWidget::}{show()} makes the widget visible.
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| 88 |
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| 89 | Line 11 makes the QApplication enter its event loop. When a Qt
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| 90 | application is running, events are generated and sent to the
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| 91 | widgets of the application. Examples of events are mouse presses
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| 92 | and key strokes. When you type text in the text edit widget, it
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| 93 | receives key pressed events and responds by drawing the text
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| 94 | typed.
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| 95 |
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| 96 | To run the application, open a command prompt, and enter the
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| 97 | directory in which you have the \c .cpp file of the program. The
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| 98 | following shell commands build the program.
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| 99 |
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| 100 | \code
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| 101 | qmake -project
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| 102 | qmake
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| 103 | make
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| 104 | \endcode
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| 105 |
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| 106 | This will leave an executable in the \c part1 directory (note that
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| 107 | on Windows, you may have to use \c nmake instead of \c make. Also,
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| 108 | the executable will be placed in part1/debug or part1/release). \c
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| 109 | qmake is Qt's build tool, which takes a configuration file. \c
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| 110 | qmake generates this for us when given the \c{-project} argument.
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| 111 | Given the configuration file (suffixed .pro), \c qmake produces a
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