I am using a `ListField` for my app to show the data in a list. Now my requirement is that i want to increase the row height of the selected item of the list.

For this, i created a `GridFieldManager` and populated my list using this manager. I then override the `onFocus()` method of this manager. But, this method is never invoked. As a result i am unable to increase the height of the selected row item.

Please help.