<page xmlns="http://projectmallard.org/1.0/" xmlns:its="http://www.w3.org/2005/11/its" xmlns:xi="http://www.w3.org/2001/XInclude" type="guide" style="task" id="button.vala" xml:lang="de">

  <info>

  <title type="text">Knopf (Vala)</title>

    <link type="guide" xref="beginner.vala#buttons"/>

    <link type="seealso" xref="GtkApplicationWindow.vala"/>

    <revision version="0.1" date="2012-02-21" status="stub"/>

    <credit type="author copyright">

      <name>Tiffany Antopolski</name>

      <email its:translate="no">tiffany.antopolski@gmail.com</email>

      <years>2012</years>

    </credit>

    <desc>A button widget which emits a signal when clicked</desc>

    <mal:credit xmlns:mal="http://projectmallard.org/1.0/" type="translator copyright">

      <mal:name>Mario Blättermann</mal:name>

      <mal:email>mario.blaettermann@gmail.com</mal:email>

      <mal:years>2011, 2013</mal:years>

    </mal:credit>

  </info>

  <title>Knopf-Widget</title>

  <media type="image" mime="image/png" src="media/button.png"/>

  
A button widget connected to a simple callback function.

/* A window in the application */

public class MyWindow : Gtk.ApplicationWindow {

	/* The constructor of the window */

	internal MyWindow (MyApplication app) {

		Object (application: app, title: "GNOME Button");

		var button = new Gtk.Button.with_label ("Click Me");

		button.clicked.connect (this.reverse_label);

		button.show ();

		this.window_position = Gtk.WindowPosition.CENTER;

		this.set_default_size (250,50);

		this.add (button);

	}

	/* The callback function connected to the

	 * 'clicked' signal of the button.

	 */

	void reverse_label (Gtk.Button button) {

		button.label = button.label.reverse ();

	}

}

/* This is the application. */

public class MyApplication : Gtk.Application {

	/* This is the constructor */

	internal MyApplication () {

		Object (application_id: "org.example.MyApplication");

	}

	/* Override the activate signal of GLib.Application */

	protected override void activate () {

		new MyWindow (this).show ();

	}

}

/* main creates and runs the application */

public int main (string[] args) {

	return new MyApplication ().run (args);

}

  In this sample we used the following:

  <link href="http://www.valadoc.org/gtk+-3.0/Gtk.Button.html">Gtk.Button</link>

</page>