BrowserWindowOpener without two phase action

Hi all,

i tried to search the Net but so far was not lucky to get my Answer.
I have a MultiSelect-Table and a DisplayPDF-Button on the Bottom.

What I want to do is to to let the User select 1 or more Items in the Table.
When he clicks the Button it gets the selected Items and creates the PDF-Resources based on the Selection and opens them in new Browser Tabs.

From the Documentation i got that I have to use the BrowserWindowOpener and extend a Button.
Can I change or set the resource only on the Button Click?
Is it really required that I have a Button “Generate PDF” and a second Button “Display PDF”?

Also any Idea how I can open mutliple new Tabs on 1 Click?
Can Vaadin 7.1 fore a Push to open new Tabs from the ServerSide?

Thanks for any Ideas