I\'m trying to convert a cellTable into adatagrid, because I want to add a search handler later and therefor I need fixed column headers. At the mo
DataGrid requires to be put in a LayoutPanel or Panel that implements the ProvidesResize interface to be visible. ScrollPanel implements that interface.
Furthermore this chain of LayoutPanels from your DataGrid up to your root element/panel has to be unbroken. That seems to be the case in your panel hierarchy.
Finally you have to use the RootLayoutPanel instead of the RootPanel to add your LayoutPanels. So did you make sure that you add your SimpleLayoutPanel to the RootLayoutPanel ?
Also refer to this GWT: DataGrid - set height 100% not rendering properly