I am not sure why your example is not working. may be you can share your code with us. Meanwhile I created table with XML view using Fiori Fast design tool and below is how my XML looks like,
<core:View
controllerName="mycontoller"
xmlns:table="sap.ui.table"
xmlns:commons="sap.ui.commons"
xmlns:core="sap.ui.core">
<table:Table
id="mytable"
selectionMode="Single"
rows="{/GRMaterialDetails}"
rowSelectionChange="onRowSelect">
<table:columns>
<table:Column>
<table:label>
<commons:Label
text="Material">
</commons:Label>
</table:label>
<table:template>
<commons:TextField
value="{Material}">
</commons:TextField>
</table:template>
</table:Column>
<table:Column>
<table:label>
<commons:Label
text="Description">
</commons:Label>
</table:label>
<table:template>
<commons:TextField
value="{Description}">
</commons:TextField>
</table:template>
</table:Column>
</table:columns>
<table:rows>
</table:rows>
</table:Table>
</core:View>
also one suggestion is do not use DataTable as it is deprecated. refer SAPUI5 SDK - Demo Kit instead of that use Table.
Regards,
Chandra