function listenBackButton() {
var lastClickBackTime = 0;
var closeWidget = function closeWidget() {
api.addEventListener({
name: 'keyback'
}, function(ret, err){
var timestamp=new Date().getTime();
if(timestamp - lastClickBackTime > 2000){
api.toast({
msg: '再按一次返回键退出'+api.appName,
duration:2000,
location: 'bottom'
});
lastClickBackTime = timestamp;
}else {
api.closeWidget({
id: 'A6908760571803'
});
}
});
}
return closeWidget();
}