为什么从邻近信标API观察到的方法beaconinfo.getfor返回错误请求（响应代码= 400）？

Question

我正在尝试使用API​​_KEY从在我的Google开发者控制台项目中注册的信标中获取附件。如Proximity Beacon API中所述，可以通过仅使用API​​密钥并在POST请求中发送正文来进行请求。 我已经完成了下面显示的所有操作。 1）发出http请求的方法：

 public String getAttachments(String beaconname, String account,String data) {

    //beacon name =  beacons/3!....
    //acountname = emailused;
   //data = json body

    String token = null;

    String SCOPE = "oauth2:https://www.googleapis.com/auth/userlocation.beacon.registry";

    String result = null;


    try {

        token = GoogleAuthUtil.getToken(getActivity(), account, SCOPE);
        Log.w("Token", token);
    } catch (IOException e) {
        e.printStackTrace();
    } catch (GoogleAuthException e) {
        e.printStackTrace();
    }
    BufferedReader bufferedReader = null;
    HttpURLConnection httpURLConnection = null;
    try {
        URL url = new URL("https://proximitybeacon.googleapis.com/v1beta1/beaconinfo:getforobserved?key="+API_KEY);
        Log.w("URL", url.toString());


        httpURLConnection = (HttpURLConnection) url.openConnection();
        httpURLConnection.setRequestMethod("POST");
        httpURLConnection.setRequestProperty("Content-Type", "application/json; charset=utf-8");
        httpURLConnection.setRequestProperty("Accept","application/json");
        httpURLConnection.setRequestProperty("Authorization", "Bearer " + token);
        httpURLConnection.setDoOutput(true);
        httpURLConnection.setDoInput(true);


        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(httpURLConnection.getOutputStream(),"UTF-8"));

        writer.write(data);
        writer.flush();
        writer.close();
        Log.w("data sent",data);


        int resposnecode = httpURLConnection.getResponseCode();
        String responsemessage = httpURLConnection.getResponseMessage();
        Log.e("Response code", resposnecode + "");
        Log.e("Response message",responsemessage);

        bufferedReader = new BufferedReader(new InputStreamReader(httpURLConnection.getInputStream(),"UTF-8"));
        String line = null;
        StringBuilder builder = new StringBuilder();
        while ((line = bufferedReader.readLine()) != null) {
            builder.append(line);
        }

        result = builder.toString();


    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {

        try {
            httpURLConnection.disconnect();
            bufferedReader.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    return result;
}

我与此发布请求一起发送的正文（上述方法中使用的数据参数）为：

 { "observations":[  
  {  
     "advertisedId":{  
        "type":"EDDYSTONE",
        "id":"vv8QICkg/0QBAwASb9z/Ug=="
     },
     "timestampMs":"2018-11-20T10:31:02.972000000Z"
  }],"namespacedTypes":[  
  "true-bla-020202/Bye"]} 

我收到错误请求，代码为400。信标在信标仪表板中具有两个附件，并具有POST正文中提到的名称空间。我从几天开始一直没有成功。