Flutter之Timer实现短信验证码获取60s倒计时功能的代码

factory Timer(Duration duration, void callback()) {
  if (Zone.current == Zone.root) {
   // No need to bind the callback. We know that the root's timer will
   // be invoked in the root zone.
   return Zone.current.createTimer(duration, callback);
  }
  return Zone.current
    .createTimer(duration, Zone.current.bindCallbackGuarded(callback));
 }

factory Timer.periodic(Duration duration, void callback(Timer timer)) {
  if (Zone.current == Zone.root) {
   // No need to bind the callback. We know that the root's timer will
   // be invoked in the root zone.
   return Zone.current.createPeriodicTimer(duration, callback);
  }
  var boundCallback = Zone.current.bindUnaryCallbackGuarded<Timer>(callback);
  return Zone.current.createPeriodicTimer(duration, boundCallback);
 }

 Timer _timer;
 int _timeCount = 60;

onTap: () {
   _startTimer();
},

void _startTimer() {
  ToastUtil.showTips('短信验证码已发送，请注意查收');
  _timer = Timer.periodic(Duration(seconds: 1), (Timer timer) => {
   setState(() {
    if(_timeCount <= 0){
     _autoCodeText = '重新获取';
     _timer.cancel();
     _timeCount = 60;
    }else {
     _timeCount -= 1;
     _autoCodeText = "$_timeCount" + 's';
    }
   })
  });
 }