flutter-template/lib/core/widgets/count_down_button.dart

import 'dart:async';

import 'package:flutter/material.dart';

/// 带倒计时的发送按钮（常用于短信验证码）。
///
/// 倒计时结束后自动恢复可点击状态。
class CountDownButton extends StatefulWidget {
  const CountDownButton({
    super.key,
    required this.onSend,
    this.label = '发送验证码',
    this.countingLabel = '重新发送',
    this.seconds = 60,
  });

  final VoidCallback onSend;
  final String label;
  final String countingLabel;
  final int seconds;

  @override
  State<CountDownButton> createState() => _CountDownButtonState();
}

class _CountDownButtonState extends State<CountDownButton> {
  int _remaining = 0;
  Timer? _timer;

  bool get _isCounting => _remaining > 0;

  void _start() {
    widget.onSend();
    setState(() => _remaining = widget.seconds);
    _timer = Timer.periodic(const Duration(seconds: 1), (t) {
      if (_remaining <= 1) {
        t.cancel();
        if (mounted) setState(() => _remaining = 0);
      } else {
        if (mounted) setState(() => _remaining--);
      }
    });
  }

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

  @override
  Widget build(BuildContext context) {
    return TextButton(
      onPressed: _isCounting ? null : _start,
      child: Text(
        _isCounting ? '${widget.countingLabel}(${_remaining}s)' : widget.label,
      ),
    );
  }
}