Flutter中audioplayers库报错：String无法赋值给Source参数

在使用audioplayers库实现音频播放按钮时，执行代码出现以下类型错误：

The argument type 'String' can't be assigned to the parameter type 'Source'

报错代码片段：

playMusic() async {
  await audioPlayer.play(url);
}

原因分析 #

audioplayers库v1.0.0及以上版本对API进行了更新：play()方法不再直接接收字符串格式的URL，而是要求传入Source类型的对象（如UrlSource、AssetSource等）。你参考的教程代码基于旧版本库编写，因此出现类型不兼容问题。

解决方案 #

有两种可行的修改方式：

方式1：直接传入UrlSource实例 #

修改playMusic方法，将字符串URL包装为UrlSource对象传入play()：

playMusic() async {
  await audioPlayer.play(UrlSource(url));
}

方式2：利用已设置的音频源 #

由于你在initState中已经通过audioPlayer.setSourceUrl(url)设置了音频源，也可以直接调用无参数的play()方法：

playMusic() async {
  await audioPlayer.play();
}

修改后的完整代码 #

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

class AudioPlayerUrl extends StatefulWidget {
  @override
  _AudioPlayerUrlState createState() => _AudioPlayerUrlState();
}

class _AudioPlayerUrlState extends State<AudioPlayerUrl> {
  AudioPlayer audioPlayer = AudioPlayer();
  PlayerState audioPlayerState = PlayerState.paused;
  String url = 'https://www.soundhelix.com/examples/mp3/SoundHelix-Song-13.mp3';

  int timeProgress = 0;
  int audioDuration = 0;

  Widget slider() {
    return Container(
      width: 300.0,
      child: Slider.adaptive(
          value: timeProgress.toDouble(),
          max: audioDuration.toDouble(),
          onChanged: (value) {
            seekToSec(value.toInt());
          }),
    );
  }

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

    audioPlayer.onPlayerStateChanged.listen((PlayerState state) {
      setState(() {
        audioPlayerState = state;
      });
    });

    audioPlayer.setSourceUrl(url);
    audioPlayer.onDurationChanged.listen((Duration duration) {
      setState(() {
        audioDuration = duration.inSeconds;
      });
    });
    audioPlayer.onPositionChanged.listen((Duration position) async {
      setState(() {
        timeProgress = position.inSeconds;
      });
    });
  }

  @override
  void dispose() {
    audioPlayer.release();
    audioPlayer.dispose();
    super.dispose();
  }

  playMusic() async {
    await audioPlayer.play();
  }

  pauseMusic() async {
    await audioPlayer.pause();
  }

  void seekToSec(int sec) {
    Duration newPos = Duration(seconds: sec);
    audioPlayer.seek(newPos);
  }

  String getTimeString(int seconds) {
    String minuteString =
        '${(seconds / 60).floor() < 10 ? 0 : ''}${(seconds / 60).floor()}';
    String secondString = '${seconds % 60 < 10 ? 0 : ''}${seconds % 60}';
    return '$minuteString:$secondString';
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
          alignment: Alignment.center,
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              IconButton(
                  iconSize: 50,
                  onPressed: () {
                    audioPlayerState == PlayerState.playing
                        ? pauseMusic()
                        : playMusic();
                  },
                  icon: Icon(audioPlayerState == PlayerState.playing
                      ? Icons.pause_rounded
                      : Icons.play_arrow_rounded)),
              Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  Text(getTimeString(timeProgress)),
                  SizedBox(width: 20),
                  Container(width: 200, child: slider()),
                  SizedBox(width: 20),
                  Text(getTimeString(audioDuration))
                ],
              )
            ],
          )),
    );
  }
}

内容的提问来源于stack exchange，提问作者G G