Here is a simple example using the Ruby Console:

Show the current material:

 > printf "%s\n", Sketchup.active_model.materials.current.name
 \[Color_D05]
 nil

Select a new material in the materials window, check the current material again:

 > printf "%s\n", Sketchup.active_model.materials.current.name
 \[Color_D05]
 nil

Fill a face with the new material, then check the current material:

 > printf "%s\n", Sketchup.active_model.materials.current.name
 \[Color_F09]
 nil

Sketchup.active_model.materials.current does not change until the last step

I am writing a script to change the material for specific part of the model. The idea is that the user will select a material from the Materials window then they will run the script which will use the current material to change some parts of the active model. To get the current material I am using Sketchup.active_model.materials.current. This seems to return the last material that was used (i.e. you actually have to apply it to a face), selecting a new material in the Materials window is not sufficient to change the value of Sketchup.active_model.materials.current.

Any suggestions on how I can determine the material that is selected in the Materials window?