MIDP Style Guide for the Java 2 Platform, Micro Edition

4.2 Onscreen Indicators

In addition to the title and ticker, a MIDP implementation can also reserve screen space for other purposes. For example, the MIDP Reference Implementation also renders a signal strength indicator, battery indicator, trust indicator (see Chapter 15 for more information), input mode indicator (see Chapter 6 for more information), scroll indicator, and the labels of abstract commands (see Chapter 12). It could, but does not, put a network activity indicator on the screen. Figure 4.5 points out these indicators and labels.

Within some contexts, a volume indicator also may be helpful.

MIDP Implementors

Strongly Recommend: Follow your device conventions as much as possible when designing the layout of your MIDP screens. Consistency among Java applications and native applications makes using MIDlets a more predictable experience for users.

Consider: Include an indicator that turns on when a MIDlet uses airtime. (All MIDP implementations must provide a visual network-usage indicator. If your device has such an indicator on its body, that is sufficient to satisfy the MIDP 2.0 Specification [19].)

Strongly Recommend: If you provide an onscreen network-usage indicator or a trust indicator, do not put them in the application area. For security, these indicators should not be controlled by the Java application. Instead, put them in a part of the screen that is controlled by the system.