Detection of Talkback

[jerome-micucci]

Sorry for my basic problem : just I want to detect if Talkback is activated or not.
Then I define a global variable TalkbackFlag and I put this lines just after my init function (called by "deviceready"):

var TalkbackFlag;
function init() {
MobileAccessibility.isTalkBackRunning(
function (flag) {
alert(TalkbackFlag); // undefined
TalkbackFlag = flag;
alert(TalkbackFlag); // true or false
}
);
nextStep();
}
function nextStep() {
alert(TalkbackFlag); // always undefined :(
}

I don't understand why my function nextStep() get always an undefined value for my var TalkbackFlag ?
Thanks for explanation...