Blackberry Smartphones Specifications download pdf (Page 43)

Containers

Application screens

Multiple screens can be open on a BlackBerry® device at one time, but users can view only one screen at a time. When multiple

screens are open, they are organized in a stack. The screen at the top of the stack is the active screen. When an application

displays a screen, the BlackBerry® Java® Virtual Machine pushes it to the top of the stack. When a screen closes, the BlackBerry

Java Virtual Machine deletes the screen from the top of the stack and displays the next screen on the stack. The application

redraws the screen as necessary.

Users can perform the following common actions on screens:

Action User interaction

Move around the screen. Move a finger on the trackpad or touch screen.

Open the menu. Press the Menu key.

Invoke an action in the menu.

• Click or tap the item.

• When an item is highlighted in the menu, press the Menu key.

Switch applications.

• Press the Alt key and the Escape key.

• Hold the Menu key.

Switch between portrait view and landscape view on

BlackBerry devices with a touch screen.

Turn the device sideways.

Close an application. Click Close in the menu.

Return to the Home screen without closing the

application screen.

Press the End key.

Best practice: Designing application screens

• Delete your application screen from the stack when users close a screen. If you use standard components, the BlackBerry®

device automatically deletes screens from the stack.

• Repaint the screen judiciously. Your BlackBerry device application should not perform unnecessary screen repaints.

• Use a limited number of nested layouts. The more nested layouts that you use to build your screen, the longer it takes for

the BlackBerry device to render the screen.

• Prompt users with a dialog box to save any unsaved data before closing a screen.

• Avoid hardcoding color values. The color values that you choose might not work with the theme that users have selected.

Guidelines for layout

UI Guidelines

Containers

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Blackberry Smartphones Specifications Page 43