Android and iOS have a concept of a "density independent pixel" so your layouts look the same on devices with different densities and screen sizes.
Up until now I've written code to manually space elements using pixels (i.e. I want this button to be 10 pixels from the left side of the screen). This is great on a Curve, but when I load it up on a Bold the resolution is much higher, so 10 pixels is a much smaller physical space.
What are the best practices for multiple screen sizes on BlackBerry? Is there any easy way to define a density independent pixel? RIM seems to not offer much in terms of documentation or APIs to make this easy.
Points are density independent pixels (to a good degree of accuracy).
For BlackBerry, the most relevant class is net.rim.device.api.ui.Ui which defines a UNITS_pt constant (and a UNITS_px constant), a convertSize method to convert between points and pixels (since operations on Graphics take pixels instead of points).
A useful methodology for BlackBerry apps is to take everything in relation to your font sizes, which you define in points - there's a version of net.rim.device.api.ui.Font.derive that takes a units parameter and makes it easy to get fonts with a particular point size.
Of course, you can't take anything for granted - defining things in points will make things easier, but with BlackBerry you deal with lots of different pixel densities and aspect ratios so test thoroughly, at least on the simulators.
来源：https://stackoverflow.com/questions/3451738/developing-for-multiple-screen-sizes-on-blackberry