Firstly there's no need to refactor ready made UiBinder if it written well. This's a great GWT framework allowing separation of logic from view. If you reject it your project will be very difficult to maintain.
Secondly one and the same GWT project can contain the view implemented both in Java code and in UiBinder xml files. This situation occurs with a support of old projects where UiBinder wasn't yet. Uibinder is a much more modern approach which has many benefits. That is if you for some reason prefer declare view only in Java code without xml then write it in Java code. And this will coexist and work properly.
And most importantly present-day GWT Designer has support UiBinder. Otherwise, no one would use it.