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<h1 align="center">Qt Jambi Tutorial 3 - Family Values<br /><small></small></h1>
<p align="center"><img src="images/tutorial3-example.png" alt="Screenshot of Chapter 3" /></p><p>This example shows how to create parent and child widgets.</p>
<p>We'll keep it simple and use just a single parent and a lone child.</p>
<pre> public class FamilyValues
{
public static void main(String args[])
{
QApplication.initialize(args);
QWidget window = new QWidget();
window.resize(200, 120);
QPushButton quit = new QPushButton("Quit", window);
quit.setFont(new QFont("Times", 18, QFont.Weight.Bold.value()));
quit.setGeometry(10, 40, 180, 40);
quit.clicked.connect(QApplication.instance(), "quit()");
window.setWindowTitle("FamilyValues");
window.show();
QApplication.exec();
}
}</pre>
<a name="line-by-line-walkthrough"></a>
<h2>Line by Line Walkthrough</h2>
<pre> QWidget window = new QWidget();</pre>
<p>Here we simply create a plain widget object. The <a href="gui/QWidget.html"><tt>QWidget</tt></a> class is the base class of all user interface objects. The widget is the atom of the user interface: It receives mouse, keyboard and other events from the window system, and paints a representation of itself on the screen. A widget is clipped by its parent and by the widgets in front of it.</p>
<p>A widget that isn't embedded in a parent widget, like this particular widget, is called a window. Usually, windows have their own window frame and taskbar entry, provided by the window system. A widget without a parent widget is always an independent window. Its initial position on the screen is controlled by the window system.</p>
<pre> window.resize(200, 120);</pre>
<p>We set the window's width to 200 pixels and its height to 120 pixels.</p>
<pre> QPushButton quit = new QPushButton("Quit", window);</pre>
<p>A child is born. This <a href="gui/QPushButton.html"><tt>QPushButton</tt></a> is created with a parent widget <tt>(window)</tt>. A child widget is always displayed within its parent's area. When displayed, it is clipped by its parent's bounds. By default, it is rooted at the top-left corner of its parent, at position (0, 0).</p>
<pre> quit.setGeometry(10, 40, 180, 40);</pre>
<p>The <a href="gui/QWidget.html"><tt>QWidget</tt></a>.setGeometry() function takes four arguments: The first two arguments are the x and y coordinates of the button's top-left corner. The coordinates are relative to the parent widget. The last two arguments are the button's width and height. The result is a button that extends from position (10, 40) to position (190, 80).</p>
<pre> window.show();</pre>
<p>When a parent widget is shown, it will call show for all its children (except those that were explicitly hidden using <a href="gui/QWidget.html"><tt>QWidget</tt></a>.hide()).</p>
<a name="running-the-application"></a>
<h2>Running the Application</h2>
<p>The button no longer fills the entire window. Instead, it stays at position (10, 40) within the window and with a size of (180, 40), because of the <a href="gui/QWidget.html"><tt>QWidget</tt></a>.setGeometry() call.</p>
<a name="exercises"></a>
<h2>Exercises</h2>
<p>Try resizing the window. How does the button change? What happens to the button's height if you run the program with a bigger font? What happens if you try to make the window really small?</p>
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