flutter - 按下按钮时颤振倒计时开始

Question

所以我正在尝试制作一个短信验证器。我需要一个按钮来发送短信，然后它需要开始倒计时，这样你就不能再按下按钮了。我在互联网上找到了这段代码（https://dartpad.dev/23c25b17a8d663ea8c01b18eae38b2ab?），问题是它在页面打开后首先开始倒计时，而我需要完全相反，一旦页面首先打开你按下按钮，然后看到倒计时和循环重复。

import 'dart:async';

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  static const _timerDuration = 30;
  StreamController _timerStream = new StreamController<int>();
  int timerCounter;
  Timer _resendCodeTimer;
  
  @override
  void initState() {
    activeCounter();
    
    super.initState();
  }
  
  @override
  dispose(){
    _timerStream.close();
    _resendCodeTimer.cancel();
    
    super.dispose();
  }
  
  
  activeCounter(){
    _resendCodeTimer =
    new Timer.periodic(Duration(seconds: 1), (Timer timer) {
      if (_timerDuration - timer.tick > 0)
        _timerStream.sink.add(_timerDuration - timer.tick);
      else {
        _timerStream.sink.add(0);
        _resendCodeTimer.cancel();
      }
    });
  }
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: StreamBuilder(
              stream: _timerStream.stream,
              builder: (BuildContext ctx,
                  AsyncSnapshot snapshot) {
                return SizedBox(
                  width: 300,
                  height: 30,
                  child:RaisedButton(
                  textColor: Theme.of(context)
                      .accentColor,
                  child: Center(
                      child:
                      snapshot.data == 0 ?
                      Text('send code again')
                          : Row(
                        mainAxisAlignment: MainAxisAlignment.center,
                        children: <Widget>[
                          Text(' button will be enable after ${snapshot.hasData ? snapshot.data.toString() : 30} seconds '),
                        ],)
                  ),
                  onPressed: snapshot.data == 0 ? () {
                    // your sending code method

                    _timerStream.sink.add(30);
                    activeCounter();
                  } : null,
                )
                );
              },
            ),
      ),
    );
  }
}

标签： flutter

Answer 1

只需像这样更改您的 initState() ：

@override
void initState() {
_timerStream.sink.add(0); //add this line

super.initState();
}