Users touch the screen with their fingertips, so touch targets (also called hit areas) for UI components should be large enough for users to use without frustration. If you use BlackBerry UI components, you don’t need to worry about the size of the touch target for each UI component. The sizes are designed to be large enough for users to touch with a finger without having to hit the target precisely.
If you create custom UI components, remember that the size of the touch target depends on the ppi of the screen. If you are designing your app for different BlackBerry devices, create a touch target for the pixel density of each screen size.
Best practices for custom UI components
Create touch targets. For BlackBerry smartphones, create touch targets that are at least 101 x 101 pixels (7.2 mm).
Make the size of the touch target larger than the visible UI component. Provide enough space around each component so that users can initiate an action easily. The extra space provides leniency for users whose attention is divided or those who are on the go.
For check boxes and radio buttons, create a touch target area for the entire row and the associated label. These UI components have small visible areas.
Make the size of the release area larger than the visible UI component. The extra space allows for imprecise interactions, such as when a finger moves after initially touching the screen.
Test the size of each touch target with your users.