I have a problem when I want to mask a grid panel the first time is loading.
I create a tab that has this grid and this page takes many minutes to load, so I want to apply the mask on it.
If I try to mask the tab, I can't obviously because it isn't completely created. I put the variable of the grid like this:
Looks like you are using GWT-Ext. Not having worked with GWT-Ext I cannot offer any suggestions for it.
However, you might want to consider GWT LazyPanel or something like a GlassPanel I personally would prefer the LazyPanel as the glass panel will block all user interaction with the whole UI.
In future, while posting code, please UseCodeTags I have edited out your original post this time. As you can see the code tags make the code much more readable and easy to understand.