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123 lines
5.3 KiB
123 lines
5.3 KiB
14 years ago
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/tutorial.doc:303 -->
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>Qt Tutorial - Chapter 3: Family Values</title>
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<style type="text/css"><!--
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fn { margin-left: 1cm; text-indent: -1cm; }
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a:link { color: #004faf; text-decoration: none }
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a:visited { color: #672967; text-decoration: none }
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body { background: #ffffff; color: black; }
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--></style>
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</head>
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<body>
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<table border="0" cellpadding="0" cellspacing="0" width="100%">
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<tr bgcolor="#E5E5E5">
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<td valign=center>
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<a href="index.html">
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<font color="#004faf">Home</font></a>
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<font color="#004faf">All Classes</font></a>
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<font color="#004faf">Main Classes</font></a>
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<font color="#004faf">Annotated</font></a>
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<font color="#004faf">Grouped Classes</font></a>
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<font color="#004faf">Functions</font></a>
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</td>
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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Qt Tutorial - Chapter 3: Family Values</h1>
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<p> <center><img src="t3.png" alt="Screenshot of tutorial three"></center>
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<p> This example shows how to create parent and child widgets.
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<p> We'll keep it simple and use just a single parent and a lone child.
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<p> <pre>/****************************************************************
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**
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** Qt tutorial 3
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**
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****************************************************************/
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#include <<a href="qapplication-h.html">qapplication.h</a>>
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#include <<a href="qpushbutton-h.html">qpushbutton.h</a>>
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#include <<a href="qfont-h.html">qfont.h</a>>
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#include <<a href="qvbox-h.html">qvbox.h</a>>
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int main( int argc, char **argv )
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{
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<a href="qapplication.html">QApplication</a> a( argc, argv );
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<a href="qvbox.html">QVBox</a> box;
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box.<a href="qwidget.html#resize">resize</a>( 200, 120 );
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<a href="qpushbutton.html">QPushButton</a> quit( "Quit", &box );
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quit.<a href="qwidget.html#setFont">setFont</a>( QFont( "Times", 18, QFont::Bold ) );
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QObject::<a href="qobject.html#connect">connect</a>( &quit, SIGNAL(<a href="qbutton.html#clicked">clicked</a>()), &a, SLOT(<a href="qapplication.html#quit">quit</a>()) );
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a.<a href="qapplication.html#setMainWidget">setMainWidget</a>( &box );
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box.<a href="qwidget.html#show">show</a>();
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return a.<a href="qapplication.html#exec">exec</a>();
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}
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</pre>
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<p> <h2> Line-by-line Walkthrough
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</h2>
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<a name="1"></a><p> <pre> #include <<a href="qvbox-h.html">qvbox.h</a>>
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</pre>
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<p> We add an include of qvbox.h to get the layout class we'll use.
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<p> <pre> <a href="qvbox.html">QVBox</a> box;
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</pre>
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<p> Here we simply create a vertical box container. The <a href="qvbox.html">QVBox</a> arranges
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its child widgets in a vertical row, one above the other, handing out
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space according to each child's <a href="qwidget.html#sizePolicy">QWidget::sizePolicy</a>().
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<p> <pre> <a name="x2300"></a> box.<a href="qwidget.html#resize">resize</a>( 200, 120 );
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</pre>
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<p> We set its width to 200 pixels and the height to 120 pixels.
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<p> <pre> <a href="qpushbutton.html">QPushButton</a> quit( "Quit", &box );
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</pre>
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<p> A child is born.
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<p> This <a href="qpushbutton.html">QPushButton</a> is created with both a text ("Quit") and a parent
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(box). A child widget is always on top of its parent. When
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displayed, it is clipped by its parent's bounds.
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<p> The parent widget, the QVBox, automatically adds the child centered in
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its box. Because nothing else is added, the button gets all the space
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the parent has.
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<p> <pre> <a name="x2302"></a> box.<a href="qwidget.html#show">show</a>();
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</pre>
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<p> When a parent widget is shown, it will call show for all its children
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(except those on which you have done an explicit <a href="qwidget.html#hide">QWidget::hide</a>()).
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<p> <h2> Behavior
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</h2>
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<a name="2"></a><p> The button no longer fills the entire widget. Instead, it gets a
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"natural" size. This is because there is now a new top-level widget,
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which uses the button's size hint and size change policy to set the
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button's size and position. (See <a href="qwidget.html#sizeHint">QWidget::sizeHint</a>() and <a href="qwidget.html#setSizePolicy">QWidget::setSizePolicy</a>() for more information about these functions.)
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<p> (See <a href="tutorial1-01.html#compiling">Compiling</a> for how to create a
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makefile and build the application.)
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<p> <h2> Exercises
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</h2>
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<a name="3"></a><p> Try resizing the window. How does the button change? What is the
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button's size-change policy? What happens to the button's height if
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you run the program with a bigger font? What happens if you try to
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make the window <em>really</em> small?
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<p> You're now ready for <a href="tutorial1-04.html">Chapter 4.</a>
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<p> [<a href="tutorial1-02.html">Previous tutorial</a>]
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[<a href="tutorial1-04.html">Next tutorial</a>]
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[<a href="tutorial.html">Main tutorial page</a>]
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<p>
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<!-- eof -->
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<p><address><hr><div align=center>
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<table width=100% cellspacing=0 border=0><tr>
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<td>Copyright © 2007
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<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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<td align=right><div align=right>Qt 3.3.8</div>
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</table></div></address></body>
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</html>
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