Flutter just_audio 包如何从字节播放音频

Question

我正在使用 just_audio 插件，它有一个功能描述：从字节流读取。

基本上，当我放置一个文件（来自 url）来播放时，我会保存文件中的字节，因此在这一步之后我想在本地播放它。

我有一个关于如何从字节流播放的问题。谁能提供一个例子如何做到这一点？我需要将其放在我的播放列表中，因此它必须是 ConcatanatingAudioSource 的子项。

我发现的唯一音频源是使用来自 Uri 的音频源。

final _playlist = ConcatenatingAudioSource(
children: [
    AudioSource.uri(
      Uri.parse(
          "https://s3.amazonaws.com/scifri-episodes/scifri20181123-episode.mp3"),
      tag: AudioMetadata(
        album: "Science Friday",
        title: "ddddd",
        artwork:
            "https://media.wnyc.org/i/1400/1400/l/80/1/ScienceFriday_WNYCStudios_1400.jpg",
      ),
    )
]
)

这就是我保存字节的方式：

void getBytes() async {
  Uri uri = Uri.parse(url);
  var rng = new Random();
// get temporary directory of device.
  Directory tempDir = await getTemporaryDirectory();
// get temporary path from temporary directory.
  String tempPath = tempDir.path;
// create a new file in temporary path with random file name.
  File file = new File('$tempPath' + (rng.nextInt(100)).toString() + '.mp3');
// call http.get method and pass imageUrl into it to get response.
  http.Response response = await http.get(uri);
// write bodyBytes received in response to file.
  await file.writeAsBytes(response.bodyBytes);
}

提前致谢

Answer 1

所以看来您需要创建自己的类作为 StreamAudioSource 的扩展。

import 'dart:typed_data';
import 'package:just_audio/just_audio.dart';

class MyJABytesSource extends StreamAudioSource {
  final Uint8List _buffer;

  MyJABytesSource(this._buffer) : super(tag: 'MyAudioSource');

  @override
  Future<StreamAudioResponse> request([int? start, int? end]) async {
    // Returning the stream audio response with the parameters
    return StreamAudioResponse(
      sourceLength: _buffer.length,
      contentLength: (end ?? _buffer.length) - (start ?? 0),
      offset: start ?? 0,
      stream: Stream.fromIterable([_buffer.sublist(start ?? 0, end)]),
      contentType: 'audio/wav',
    );
  }
}

然后像这样调用它

await thePlayer.setAudioSource(MyJABytesSource(bytes));

您可以thePlayer.play().稍后调用，但我更喜欢将其用作侦听器。

thePlayer.processingStateStream.listen((ja.ProcessingState state) {
  if (state == ja.ProcessingState.ready) {
    // I'm using flutter_cache_manager, and it serves all the file
    // under the same name, which is fine, but I think this is why
    // I need to pause before I can play again.
    // (For tracks after the first, the first plays fine.)

    // You probably won't need to pause, but I'm not sure.
    thePlayer.pause();
    thePlayer.play();
  } else if (state == ja.ProcessingState.completed) {
    // What to do when it completes.
  }
});

这样做的好处是，您实际上不需要await关键字，这在具体情况下可能很有用。我把它放在那里只是为了表明这是一个async函数。