J2ME in a Nutshell

Chapter 4. MIDlet User Interfaces

MIDlets are intended to be portable to a range of devices with widely varying input and display capabilities, ranging from the very small, mainly two-color screens and restricted keypads on pagers and cell phones to the larger, often multicolor displays and more sophisticated keyboards or handwriting recognizers available on PDAs. Creating a set of user interface components suitable for such a wide range of devices is not a simple task. One option available to the MIDP designers was to use a subset of the Abstract Windows Toolkit (AWT) or Swing components from J2SE. However, this is not really a viable solution. Resource constraints rule out the adoption of Swing, while the basic user interface model around which the AWT is based is far too complex to be used on small devices.

Both AWT and Swing are based on giving the developer maximum freedom to create a rich and complex GUI in a multiwindowed environment, in which the user might be interacting with several applications at the same time. By contrast, because of the limited screen size, cell phone users do not expect to be able to work with more than one window or even more than one MIDlet at any given time. Instead of trying to find a subset of the AWT that would be appropriate for this restricted environment, the MIDP expert group chose to introduce a much simpler set of components and a lighter, screen-based programming model. In this model, the MIDlet developer focuses more on the business ...