This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Stephen covers this topic in Chapter 10 as he takes some desktop examples from earlier in the book and discusses what it takes to run them in a mobile environment.
There are a few things you have to consider when running in the mobile environment. Some are obvious such as screen size, but there are other limitations that are less obvious. But generally, as long as you stick to JavaFX's common profile (i.e. the non-desktop-specific APIs) you won't have too much trouble. The common profile does cover most of what you would normally use anyway, so this is not a very harsh restriction.