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dart - Flutter - How to download a file from server using binary stream

问题描述

I need to be able to download and display an image from a private server. The request that I send needs to include a header with content-type and a body with sessionToken and userId. The server responds with a binary stream with the Content-type application/octet-stream.

This is the code I have right now: 

 Future<Null> _downloadFile(String url, String userId, sessionToken) async {
    Map map = {'token': sessionToken, 'UserId': userId};

    try {
      var request = await httpClient.getUrl(Uri.parse(url));
      request.headers.set('content-type', 'application/json');
      request.add(utf8.encode(json.encode(map)));
      var response = await request.close();
      var bytes = await consolidateHttpClientResponseBytes(response);
      await _image.writeAsBytes(bytes);
      userImage(_image);
    }
    catch (value){
      print(value);
    }

  }

When I try to read the response I get this error: HttpException: Content size exceeds specified contentLength. 72 bytes written while expected 0.

I've tried to google this endlessly on how to download a file from a server using a stream, but I can't find anything. What I need is something similar to the bitmap class in .NET that can take in a stream and turn it into an image.

Can anybody help me? It would be greatly appreciated.

标签： dartflutter

解决方案

我能够用这段代码成功地做到这一点：

 void getImage(String url, String userId, sessionToken) async{
    var uri = Uri.parse(url);

    Map body = {'Session': sessionToken, 'UserId': userId};
    try {
      final response = await http.post(uri,
          headers: {"Content-Type": "application/json"},
          body: utf8.encode(json.encode(body)));

      if (response.contentLength == 0){
        return;
      }
      Directory tempDir = await getTemporaryDirectory();
      String tempPath = tempDir.path;
      File file = new File('$tempPath/$userId.png');
      await file.writeAsBytes(response.bodyBytes);
      displayImage(file);
    }
    catch (value) {
      print(value);
    }
  }

谢谢您的帮助 ：）

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