How to detect last call to server in GWT?

I want to detect last asy开发者_StackOverflow中文版nchronous call to server, because i want to display loading box before all javascript code download and display successfully.

Like gmail- gmail display loading box after sign in before all javascript code download and display properly

Please help me

Thanks

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I would suggest to use a unified RPC caller that handle retries on errors and display your loading box.