J2ME in a Nutshell

Name

Gauge

Synopsis

This class is an Item that can be used as either a progress bar or a slider. The Gauge displays a fixed range of integer values together with the current value. The maximum value of the range and the initial value are set when the Gauge is constructed and may subsequently be changed using the setMaxValue() and setValue() methods. The minimum value is always implicitly zero.

In normal operation, the current value would probably start at zero and be updated by application code by calling the setValue() method to reflect the progress of an ongoing operation. In this mode, the Gauge operates as a progress bar and its value cannot be changed by the user. To prevent the user changing the value, the Gauge should be made non-interactive, which can be done by setting the interactive constructor argument to false. Note that this attribute cannot be changed once the Gauge has been constructed, although its value can be obtained by calling isInteractive().

To use the Gauge as a slider, it should be made interactive. In this mode, the user can change the current value within the permitted range using a device-dependent gesture. As the value changes, the Gauge notifies the ItemStateListener for the Form on which it is displayed, which can retrieve the new value using the getValue() method.

Owing to display limitations, it may not be possible for every possible value in the allowed range to be displayed and therefore the user may have to adjust the Gauge value several times ...