As you start designing an application, decide which BlackBerry® Device Software version to develop for. The version defines the minimum set of features that you can use.
Applications are compatible with future software versions. For example, if you design an application for BlackBerry® Bold™ 9000 smartphones running BlackBerry Device Software 4.6, it can run on BlackBerry® Storm2™ 9550 smartphones running BlackBerry Device Software 5.0. You should verify the layout of each screen since some adjustments might be required to the layout and size of the UI elements.
After you decide which device software version to develop for, decide which devices to design for. If you are designing for more than one device, design the UI to accommodate the different screen sizes and resolutions among BlackBerry devices. Use BlackBerry UI components to help make the layout more extensible. You can also group BlackBerry devices according to screen size and choose a reference device for each group. If you lay out the screens for each reference device, then you do not have to design the screens for each device — but you can make adjustments if necessary.
Example 1: You choose the BlackBerry Storm2 9550 smartphone as the reference device. If you apply the layout to the BlackBerry® Pearl™ Flip Series smartphone and the BlackBerry® Pearl™ 8100 Series smartphone, you keep the UI elements the same size since there is not much difference in the resolution between the reference device and the other devices. However, you need to adjust the layout of the UI elements (for example, by wrapping some content) since the screen sizes are different.
Example 2: You choose the BlackBerry® Curve™ 8300 smartphone as the reference device. If you apply the layout to the BlackBerry Bold 9000 smartphone and the BlackBerry® Curve™ 8900 smartphone, you need to make the UI elements larger since the resolution between the reference device and the other devices is different. However, since the screen sizes are similar, you do not need to adjust the layout of the UI elements.
Verify the layout of each screen on each device that you are designing for. Try to create a UI that works the same on all of the devices running a specific version of device software. Carefully consider compromises that are made to consistency for the sake of simplifying development. Compromises should only be made when necessary.
Considerations for existing applications
If you have an existing application and you want to make it available on BlackBerry touch screen devices, you need to adjust the layout to accommodate touch interactions and different size banners, background images, and icons. For more information on touch interactions, see the "Touch screen" topic.
You also need to decide whether to display the application in portrait mode, landscape mode, or both. If you use BlackBerry UI components, the orientation mode will be handled automatically. If you develop an application using a version of the BlackBerry® Java® Development Environment earlier than version 4.7, the application runs in compatibility mode, which is designed to provide an operating environment for applications that were not developed to support touch screens. For more information on compatibility mode, see the Transitioning to Touch Screen Development Technical Note.