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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Qt Tutorial - Chapter 3: Family Values</title></head><body bgcolor="#ffffff"><p><table width="100%"><tr><td><a href="index.html"><img width="100" height="100" src="qtlogo.png"alt="Home" border="0"><img width="100"height="100" src="face.png" alt="Home" border="0"></a><td valign="top"><div align="right"><img src="dochead.png" width="472" height="27"><br><a href="classes.html"><b>Classes</b></a>- <a href="annotated.html">Annotated</a>- <a href="hierarchy.html">Tree</a>- <a href="functions.html">Functions</a>- <a href="index.html">Home</a>- <a href="topicals.html"><b>Structure</b> <font face="Arial,Helvetica,Geneva,Swiss,SunSans-Regular" align="center" size=32>Qte</font></a></div></table><p><h1 align=center>Chapter 3: Family Values</h1><br clear="all"><p><center><img src="t3.png" alt="Screenshot of tutorial three"></center><p>This example shows how to create mother and child widgets.<p>We'll keep it simple and use just a single mother (uh, family values?)and a lone child. <pre>/******************************************************************** Qt tutorial 3******************************************************************/#include <<a href="qapplication-h.html">qapplication.h</a>>#include <<a href="qpushbutton-h.html">qpushbutton.h</a>>#include <<a href="qfont-h.html">qfont.h</a>>#include <<a href="qvbox-h.html">qvbox.h</a>>int main( int argc, char **argv ){ <a href="qapplication.html">QApplication</a> a( argc, argv ); <a href="qvbox.html">QVBox</a> box; box.<a href="qwidget.html#ff9d07">resize</a>( 200, 120 ); <a href="qpushbutton.html">QPushButton</a> quit( "Quit", &box ); quit.<a href="qwidget.html#090d60">setFont</a>( <a href="qfont.html">QFont</a>( "Times", 18, QFont::Bold ) ); <a href="qobject.html#7f8e37">QObject::connect</a>( &quit, SIGNAL(clicked()), &a, SLOT(quit()) ); a.<a href="qapplication.html#7ad759">setMainWidget</a>( &box ); box.<a href="qwidget.html#200ee5">show</a>(); return a.<a href="qapplication.html#84c7bf">exec</a>();}</pre><p><h2>Line by Line Walk-Through</h2> <pre> #include <<a href="qvbox-h.html">qvbox.h</a>></pre><p>We add an include of qvbox.h, to get the layout class we'll use. <pre> <a href="qvbox.html">QVBox</a> box;</pre><p>Here we simply create a vertical box container. The QVBox arrangesits child widgets in a vertical row, one above the other, handing outspace according to each child's <a href="qwidget.html#23726d">QWidget::sizePolicy()</a>. <pre> box.<a href="qwidget.html#ff9d07">resize</a>( 200, 120 );</pre><p>We set its width to 200 pixels and the height to 120 pixels. <pre> <a href="qpushbutton.html">QPushButton</a> quit( "Quit", &box );</pre><p>A child is born.<p>This QPushButton is created with both a text, "Quit", and a mother,box. A child widget is always on top of its mother. When displayed,it is clipped by its mother's bounds.<p>The mother widget, the QVBox, automatically adds the child, centeredin its box. Since nothing else is added, the button gets all thespace the mother has. <pre> box.<a href="qwidget.html#200ee5">show</a>();</pre><p>When a mother widget is shown, it will call show for all its children(except those on which you have done an explicit <a href="qwidget.html#410481">QWidget::hide())</a>.<p><h2>Behavior</h2><p>The button no longer fills the entire widget. Instead, it gets a"natural" size. This is because there is now a new top-level widget,which uses layout management to set a good size and position for thebutton.<p><h2>Exercises</h2><p>Try resizing the window. How does the button change? What is thebutton's size change policy? What happens if you try to make thewindow <em>really</em> small?<p>You may now go on to <a href="t4.html">chapter four.</a><p>[<a href="t2.html">Previous tutorial</a>][<a href="t4.html">Next tutorial</a>][<a href="tutorial.html">Main tutorial page</a>]<p><address><hr><div align="center"><table width="100%" cellspacing="0" border="0"><tr><td>Copyright ⌨️ 快捷键说明
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