title: ExtJS accordion init component while collapsed
body: <p>I have following problem in EXTJS:
  I have an accordion layout with 2 panels.
  the first panel is for choosing an element and if you doubleclick the detail will be displayed in the second panel.</p>
  
  <p>However there is one problem:
  The elements of panel2 seems not to be initialised, so i get an "is undefined" error.</p>
  
  <p>When i open panel2 and close it, i dont have the problem.
  However opening and closing it looks creepy.</p>
  
  <p>Is there a way to initialise the elements while it is collapsed?
  or is there something like a callback in mainPanel.layout.setActiveItem(panel1)...callback:initPanel2() ?</p>