flutter-sport/lib/utils/download.dart

import 'dart:async';
import 'dart:io';

import 'package:app_installer/app_installer.dart';
import 'package:dio/dio.dart';

class DownloadStatus {
  String tag;
  String path;
  int count;
  int total;
  bool done;
  bool failed;
  DioError? error;

  DownloadStatus(
      this.tag, this.path, this.count, this.total, this.done, this.failed,{this.error});
}

/*
 * 文件下载
 * 懒加载单例
 */
class DownLoadManage {
  //用于记录正在下载的url，避免重复下载
//  var downloadingUrls = new List();
  var downloadingUrls = new Map<String, CancelToken>();

  // 单例公开访问点
  factory DownLoadManage() => _getInstance();

  // 静态私有成员，没有初始化
  static DownLoadManage? _instance;

  // 私有构造函数
  DownLoadManage._() {
    // 具体初始化代码
  }

  // 静态、同步、私有访问点
  static DownLoadManage _getInstance() {
    if (_instance == null) {
      _instance = DownLoadManage._();
    }
    return _instance!;
  }

  final StreamController<DownloadStatus> _controller =
      StreamController.broadcast();

  Stream<DownloadStatus> get stream => _controller.stream;

  /*
   *下载
   */
  Future<bool> download(url, savePath) async {
    int downloadStart = 0;
    bool fileExists = false;
    File f = File(savePath);
    if (await f.exists()) {
      downloadStart = f.lengthSync();
      fileExists = true;
    }

    print(
        "download $url $fileExists ${downloadingUrls.containsKey(url)} ${downloadingUrls[url]?.isCancelled} ${downloadingUrls.length}");
    if (fileExists &&
        downloadingUrls.containsKey(url) &&
        !(downloadingUrls[url]?.isCancelled ?? false)) {
      print("download $url $fileExists");
      //正在下载
      return false;
    }

    CancelToken cancelToken = new CancelToken();
//   downloadingUrls[url] = cancelToken;
    if (downloadingUrls[url] == null) {
      downloadingUrls[url] = cancelToken;
    }

    var dio = Dio();
    String contentLength;
    int _total = 0;
    try {
      contentLength = await _getContentLength(dio, url, cancelToken);
      print("download contentLength :$contentLength");
      _total = int.parse(contentLength);
      print("download start :$downloadStart -- contentLength: $contentLength");
      if (downloadStart >= _total) {
        stop(url);
        //存在本地文件，命中缓存
        _controller.add(
            DownloadStatus(url, savePath, downloadStart, _total, true, false));
        // done?.call();
        return true;
      }
    } catch (e) {
      print(e);
      stop(url);
      return false;
    }

    cancelToken = new CancelToken();
    downloadingUrls[url] = cancelToken;

    File tmp = File("$savePath.tmp$downloadStart");
    tmp.createSync();
    var resp = await dio
        .download(url, tmp.path,
            deleteOnError: false,
            onReceiveProgress: (index, total) {
              _controller.add(DownloadStatus(
                  url, savePath, index + downloadStart, _total, false, false));
              // print("url --- > $index, $total");
            },
            // onReceiveProgress?.call(index + downloadStart, _total),
            cancelToken: cancelToken,
            options: Options(
              followRedirects: false,
              headers: {"range": "bytes=$downloadStart-$contentLength"},
            ))
        .whenComplete(() {
      downloadingUrls.remove(url);
      print("download whenComplete $url");
    }).catchError((e) async {
      print("download catch $e");
      downloadingUrls.remove(url);
      if(e is DioError){
        _controller.add(DownloadStatus(url, savePath, 0, _total, false, true, error: e));
      }else {
        _controller.add(DownloadStatus(url, savePath, 0, _total, false, true));
      }
      // failed?.call(e);
    });
    await append(f, tmp);
    if (resp != null) {
      // done?.call();
      _controller.add(DownloadStatus(url, savePath, 0, _total, true, false));
      return true;
    }
    return false;
    // downloadingUrls.remove(url);
    // done.call();
  }

  append(File file, File tmp) async {
    IOSink ioSink = file.openWrite(mode: FileMode.writeOnlyAppend);
    await ioSink.addStream(tmp.openRead());
    await tmp.delete(); //删除临时文件
    await ioSink.close();
    print("download save file ---------file --- ${file.lengthSync()}");
  }

  /*
   * 获取下载的文件大小
   */
  Future _getContentLength(Dio dio, url, CancelToken cancelToken) async {
    try {
      Response response = await dio.head(url, cancelToken: cancelToken);
      return response.headers.value(Headers.contentLengthHeader);
    } catch (e) {
      print("download _getContentLength Failed:" + e.toString());
      return 0;
    }
  }

  void stop(String url) {
    if (downloadingUrls.containsKey(url)) {
      try {
        downloadingUrls[url]?.cancel();
      } catch (e) {
        print(e);
      }
    }
    downloadingUrls.remove(url);
  }

  bool isDowning(String url) {
    return downloadingUrls.containsKey(url);
  }
}