Newsletter sign-up

View all newsletters

Sign up for our technology specific newsletters.

Enterprise Java

Email Address:

Rich clients with the SWT and JFace

Build a GUI application using Java and the Eclipse GUI APIs

By Brian Sam-bodden and Christopher Judd, JavaWorld.com, 04/26/04

Page 2 of 5

The following are the two main frameworks that you'll learn about:

• SWT: A widget set and graphics library that provides a portable graphics API independent of the OS but that relies on the native widgets
• JFace: A model-based UI toolkit that simplifies common UI programming tasks

Standard Widget Toolkit

SWT is the foundation upon which the Eclipse IDE is built. SWT delivers the richness and responsiveness of an application build using native widgets, yet it manages to do so in an operating system-independent fashion.

The Eclipse team realized early that creating a cross-platform set of widgets is a daunting task, both in the areas of matching the functionality of mature operating-system widgets and in making the application seamlessly blend with the native applications. SWT takes a hybrid approach between those taken by AWT and Swing. Instead of using "fat native peers," SWT uses a procedural pass-through layer to the OS graphics API. This thin Java Native Interface (JNI) layer enables SWT to control the native widgets. This approach minimizes the amount of native code involved, thereby making debugging SWT a lot easier. SWT also avoids the need for a pluggable look and feel because it adopts and immediately reflects any changes to the underlying OS look and feel.

Note

Pluggable look and feel is another hotly debated topic. The Eclipse mentality is one of "uniform is better," and we certainly agree with this when it comes to commercial business software. Many other applications can certainly benefit from a pluggable look and feel in the same way that many applications benefit from the use of skins. If your application needs to support a customizable or personalized look, then Swing is the obvious choice.

The SWT approach not only makes the API simpler, but also provides tight integration with hard-to-integrate features such as drag and drop. Drag-and-drop support is another area in which Swing's implementation was plagued for a long time by bugs and inconsistencies. With SWT, any improvements in the drag-and-drop behavior of the OS are reflected in your Java applications immediately.

To resolve the least common denominator problem, SWT widgets that aren't present in a specific platform are emulated using lightweight techniques in the way that it's done in Swing, yet the components are unencumbered by any built-in patterns. A good example is the Tree widget. In Windows, Tree widgets are native components, but in Motif, they're emulated. The SWT implementation in Motif contains the Java code to provide the Tree functionality, but in Windows, using a Tree widget is simply a matter of calling the correct Windows graphics device interface (GDI) commands. Figure 1 shows the three different approaches.

Figure 1. Rendering approaches of AWT, SWT, and Swing

The SWT API is the same on all different supported platforms. Behind the scenes, SWT uses a factory pattern of sorts to plug the right implementations for a given platform. Not only do SWT applications look like they belong among other native applications, but they also feel like native applications. Figure 2 provides a graphical overview of the SWT architecture.

 

Improve efficiency with Visual Studio(r) 2010 Beta 2. - Microsoft

About Us | Advertise | Contact Us | Terms of Service/Privacy

Copyright, 2006-2008 Network World, Inc. All rights reserved.