Same problem here - i tried all I can think of (fired click event, deferred focus(), cmp.fieldEl.dom.focus(), createRange..) - some methods worked on chrome desktop but not on the iphone itself. I removed all buttons to check if these will "steal" the focus but that did not help either.
I called the methods above on the show and activate, afterrender formpanel events, but it did not work at all.
Every solution, no matter how dirty :-), will be appreciated.
My current setup:
Panel in cardlayout:
card 1: Panel with list cmp
card 2: FormPanel with 1 TextArea
All components are initiated only once, so pure initComponent() logic will fail - working with the 'activate' seems to be the best solution for me, but...