UI and navigation design
3
BlackBerry device user input and navigation
BlackBerry® devices include a keyboard, a trackwheel or trackball, and an Escape key, for input and navigation. The Escape key
provides an easy way for BlackBerry device users to go back to the previous screen or remove a menu or dialog box from the
screen.
A BlackBerry® Java Application for BlackBerry devices should use the following input and navigation model as closely as possible.
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Clicking the trackwheel or trackball typically invokes a menu.
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Pressing the Escape key changes the display to the previous screen or closes the application from the main screen.
By default, the BlackBerry screen objects provide this functionality without customization; however, you must add menu items
and additional UI and navigation logic.
Trackwheel versus Trackball
Trackball sensitivity
Trackball sensitivity refers to the amount of trackball movement that is required for the system to identify the movement as a
navigation event, and to dispatch a navigation event to the software layer. The BlackBerry® device hardware measures physical
trackball movement using units called ticks. When the number of ticks along an axis surpasses the threshold of the system or a
BlackBerry® Java Application, a navigation event along that axis is dispatched to the software layer, and the system resets the
tick count to zero. Tick counts are also reset to zero after a certain amount of idle time passes.
You can use the TrackBall API to set the trackball sensitivity. High trackball sensitivity equates to a smaller tick threshold, which
means that small trackball movements will trigger navigation events. Conversely, low trackball sensitivity equates to a larger tick
threshold, which means that larger trackball movements are required to generate navigation events.
Trackball movement
You can use the Trackball API to filter the trackball movement data that the BlackBerry® device hardware sends to the software
layer. The Trackball API can filter out movement "noise" or unwanted movements.
You can also use the Trackball API to change settings such as trackball movement acceleration. Increasing the trackball movement
acceleration setting can result in the software layer identifying trackball movements as moving at a faster rate than the rate
detected by the BlackBerry device hardware, as long as the user continually rolls the trackball. The trackball sensitivity temporarily
increases as the user rolls the trackball without pausing.
Fundamentals Guide
UI and navigation design
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