MIDP Style Guide for the Java 2 Platform, Micro Edition

13.4 Launching and Exiting MIDlet Suites

This section assumes that the MIDP implementor is using the native launch mechanism on the device so that users launch MIDlets suites in the same way as they launch native applications. It also assumes that when the user exits a MIDlet suite, they are returned to the native operating environment, not to a special MIDP environment.

MIDP Implementors

Recommend: Present a MIDlet suite with only one MIDlet in a way that enables users to directly launch the MIDlet and to exit to the application launcher after they are through. When you represent the MIDlet, you show the icon associated with the MIDlet, as opposed to the one associated with the MIDlet suite.

For example, the SmartTicket MIDlet suite contains only one MIDlet. When this MIDlet suite is installed on a device running Sun's MIDP for Palm OS, tapping the SmartTicket icon starts the SmartTicket MIDlet, the only MIDlet in the suite. Figure 13.7 shows this sequence; when the user chooses the Smart Ticket icon from the screen on the left, SmarTicket launches and the screen on the right appears.

Recommend: Represent a MIDlet suite with multiple MIDlets so that users can choose a MIDlet from the suite after launching the suite (a MIDlet Chooser screen).

For example, the Games MIDlet suite contains multiple MIDlets. As Figure 13.8 shows, when this MIDlet suite is installed on a device running Sun's MIDP for Palm OS, tapping the Games icon shows users an interim screen that enables them to choose which MIDlet in the Games MIDlet suite they would like to launch.

The MIDP 1.0 Reference Implementation, shown in Figure 13.9, took a different approach, which did not work as well in user testing. Its application launcher shows both MIDlet suites and MIDlets, and enables users to launch either. If a MIDlet suite has a single MIDlet, only the MIDlet is represented.

Users reported feeling confused because they didn't know what they were looking at. They thought that the item representing the MIDlet suite was a folder in a file system.

The MIDP 2.0 Reference Implementation, shown in Figure 13.10, now uses the same approach as Sun's MIDP for Palm OS. The application launcher shows the MIDlet suite and an interim screen if the suite has multiple MIDlets.

Sun's MIDP for Palm OS and the MIDP 2.0 Reference Implementation behave differently, however, when the user exits a MIDlet from a suite with multiple MIDlets. For example, in MIDP for Palm OS, if the user exited the WormGame MIDlet (which is a MIDlet in a suite of multiple MIDlets), the user was returned to the MIDlet Chooser screen.

The MIDP 2.0 Reference Implementation, shown in Figure 13.12, returns the user to the application launcher. In usability testing, users preferred this model. Whichever model you follow, check your design with usability tests to make sure users understand it.

MIDP Implementors

Recommend: When the user exits a MIDlet that is part of a MIDlet suite with multiple MIDlets, exit to the application launcher (Figure 13.12), not a screen to choose a MIDlet in the suite. Usability testing has shown that users become confused if they are not returned to the application launcher.