help! how to add a TextField to TableItem's cell?

[cqiao]

i want to implement the function:
double click a table's cell, the cell display a TextField in it. then, the cell gets users input string from the TextField's input box.

how can i get it ?

[cqiao]

i try to add a widget into a TableItem,but not work.
TextField<String> tf=new TextField<String>();
itemSelected.setWidget(itemIndex, tf);