flutter 倒计时按钮 代码片段

count_timer_button.dart

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:meta/meta.dart';

typedef String TextMaker(int time);

class CountTimerButton extends StatefulWidget {
  final Function onTap;
  final TextMaker textMaker;
  const CountTimerButton({
    Key key,
    @required this.onTap,
    @required this.textMaker,
    int maxSecond = maxTime,
  }) : super(key: key);

  @override
  _CountTimerButtonState createState() => _CountTimerButtonState();
}

const maxTime = 15;

class _CountTimerButtonState extends State<CountTimerButton> {
  int time = 0;
  Timer timer;

  @override
  void initState() {
    super.initState();
  }

  @override
  void dispose() {
    timer?.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return FlatButton(
      onPressed: _getTap(),
      child: Text(widget.textMaker(time)),
    );
  }

  Function _getTap() {
    if (time == 0) {
      return () => _startCountDown();
    }
    return null;
  }

  _startCountDown() {
    widget.onTap?.call();
    setState(() {
      time = maxTime;
    });
    timer?.cancel();
    timer = Timer.periodic(Duration(seconds: 1), (timer) {
      setState(() {
        time = maxTime - timer.tick;
        if (time == 0) {
          timer.cancel();
        }
      });
    });
  }
}