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