ItemRenderer通过AdvancedDataGrid上的ItemEditor显示

I'm pretty new to Flex, so there's probably a good chance I'm missing something obvious, but in the first example code, everything works as expected. When not editing the cell, it shows a centered date as plain text. When editing, it shows a DateField editor. The second example is exactly the same as far as I can tell, other than the fact that it is an I'm pretty new to Flex, so there's probably a g