The visual look and feel of Nokia Asha UI is very different from the previous Series 40 UI’s. Luckily, most of the API’s remained the same!
One major API change that affects the UI and UX has been done for the CategoryBar API; it now supports two different modes. You can use it as a tab bar (like it has been used for Full touch), and in addition as a toolbar for the most frequently used actions. At the same time the CategoryBar extension has been disabled for Nokia Asha UI. There is a fixed number of four items you can place in the Category bar, both in portrait and in landscape.
You probably remember my blog post from a while back, where I discussed this same issue but saying that actions are not allowed in the CategoryBar? Well, that still holds for the Full touch; the API change doesn’t apply there. So, when you are bringing your Full touch MIDlet to Nokia Asha and you have “played by the rules” (i.e. not having actions in your CategoryBar), you only need to consider the amount of tabs you have (only 4 possible with Nokia Asha UI, compared to 15 with Full touch).
But if you decide to create a new MIDlet for Asha and use actions in the CategoryBar, you will need to have another solution for Full touch, due to the facts described in my old post.
It’s also important to keep in mind that tabs and actions cannot be mixed in the same CategoryBar. This also comes back to the visualization of the component. So either use tabs (one item is always selected, used for changing the view) or actions (none of the items is in selected mode, used to trigger an action).
See the Nokia Asha design guidelines if you haven’t already!