Abstract Window Toolkit

The Abstract Window Toolkit (AWT) is

History

When

In J2SE 1.2, the Swing toolkit largely superseded the AWT's widgets. In addition to providing a richer set of UI widgets, Swing draws its own widgets (by using Java 2D to call into low-level subroutines in the local graphics subsystem) instead of relying on the operating system's high-level user interface module. Swing provides the option of using either the native platform's "look and feel" or a cross-platform look and feel (the "Java Look and Feel") that looks the same on all windowing systems.

Architecture

The AWT provides two levels of

• A general interface between Java and the native system, used for windowing, events, and layout managers. This API is at the core of Java GUI programming and is also used by Swing and Java 2D. It contains:
  • The interface between the native windowing system and the Java application;
  • The core of the GUI event subsystem;
  • Several layout managers;
  • The interface to
    keyboard
    ; and
  • A java.awt.datatransfer
    Clipboard and Drag and Drop
    .
• A basic set of GUI widgets such as buttons, text boxes, and menus. It also provides the
  native code to draw directly to an AWT Canvas object
  drawing surface.

Neither AWT nor Swing is inherently thread safe. Therefore, code that updates the GUI or processes events should execute on the Event dispatching thread. Failure to do so may result in a deadlock or race condition. To address this problem, a utility class called SwingWorker allows applications to perform time-consuming tasks following user-interaction events in the event dispatching thread.

Mixing AWT and Swing components

Where there is a Swing version of an AWT component it will begin with J- and should be used exclusively, replacing the AWT version. For example, in Swing, only use JButton, never Button class. As mentioned above, the AWT core classes, such as Color and Font, are still used as-is in Swing.

When drawing in Swing, use JPanel and override paintComponent(Graphics g) instead of using the AWT paint() methods.

Before

Starting in Java 6 Update 12, it is possible to mix Swing and AWT widgets without having z-order problems.^[2]

Example

import java.awt.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

public class MyApp {

    public static void main(char[] args) {
        Frame frame = new Frame("Application");
        
        frame.add(new Label("Hello!"));
        frame.setSize(500, 500);
        frame.setLocationRelativeTo(null); // Centers the window
        
        frame.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                frame.dispose(); // Releases native screen resources
            }
        });
        
        frame.setVisible(true);
    }
}

Implementation

As the AWT is a bridge to the underlying native user-interface, its implementation on a new operating system may involve a lot of work, especially if it involves any of the AWT GUI widgets, because each of them requires that its native peers be developed from scratch.

A new project, Caciocavallo, has been created, that provides an

• Swing (Java)
• Standard Widget Toolkit

References

External links

Wikibooks has a book on the topic of: Java Swings/AWT

Wikimedia Commons has media related to AWT.

• java.awt (AWT Javadoc API documentation)
• AWT documentation
• AWT/Swing
• java.awt